# Longevity blood test: The 8 biomarkers that actually matter, and why 'normal' is not 'optimal'

_By Maurice Lichtenberg · Published 2026-06-14 · Updated 2026-09-23_

A longevity blood test usually covers eight markers: fasting insulin, HOMA-IR, hs-CRP, homocysteine, HbA1c, the Omega-3 Index, ferritin and vitamin D (25-OH-D). Here is the catch. A lab "normal" range only reflects the middle 95% of a population, not your lowest-risk value, so the optimal targets are tighter: hs-CRP below 1 mg/L, a HOMA-IR near 1, an Omega-3 Index of 8% or more. Only glucose, fasting insulin and HOMA-IR need a fast of at least 8 hours. As a self-pay test in Germany, all eight cost roughly 170 to 290 euros. And several "optimal" targets are wellness goals with no outcome trials behind them.

A lab reference range only tells you whether you sit inside the middle 95% of a population, not whether your value is healthy. Here are eight markers, their tighter optimal window from peer-reviewed literature and the places where 'optimizing' does nothing. We sell neither tests nor supplements.

## On this page

- Which blood tests matter for longevity? The 8 markers and why 'normal' is not 'optimal'
- HOMA-IR and fasting insulin: How do I catch insulin resistance before blood sugar slips?
- Hs-CRP: What level is good, and what does a high value mean?
- High homocysteine: Is lowering it with folate and B vitamins worth it?
- HbA1c: When is it prediabetes, and which value is really optimal?
- Omega-3 Index: What is a good level, and what if yours is low?
- Ferritin and iron deficiency: Why 'within range' can still mean a deficiency
- Vitamin D: Deficiency, optimum, and what the big VITAL trial actually showed
- Longevity blood test optimal ranges: Table of all 8 markers

## Which blood tests matter for longevity? The 8 markers and why 'normal' is not 'optimal'

Eight markers cover most of what you can get out of a 'longevity blood test': fasting insulin, HOMA-IR, hs-CRP, homocysteine, HbA1c, the Omega-3 Index, ferritin and vitamin D (25-OH-D). Each one has an official lab reference range and a tighter, literature-cited 'optimal' window. The two most causal lipid markers, [ApoB and Lp(a)](/en/guide/apob-lpa), we deliberately do not go deep on here; they get their own guide.

Here is the spine of this guide: 'normal' is not the same as 'optimal'. A lab reference range is defined statistically, as the central 95% of a reference population. It tells you whether you fall into the middle of the distribution, not whether your value carries the lowest risk of disease and death. Those two things often come apart.

Timing matters: glucose, fasting insulin and therefore HOMA-IR need a fast (usually at least 8 hours), because HOMA-IR is explicitly computed from fasting glucose and fasting insulin. [1] HbA1c, hs-CRP, homocysteine, the Omega-3 Index, ferritin and 25-OH-D do not. Homocysteine is reported as a fasting value in most reference studies, but a non-fasting sample is acceptable for screening. [6]

One point where a lot of results flip: hs-CRP and ferritin are so-called acute-phase reactants, markers that spike with any inflammation. Do not test them within about two to three weeks of an infection, injury, surgery or vaccination, or the result is uninterpretable for its intended purpose. Retest when you are well again. [2][12]

A complete panel adds a few cheap basics this guide does not cover in depth: creatinine with eGFR for the kidneys, ALT and GGT for the liver, a blood count, and ApoB and Lp(a) for heart risk. The statutory Check-up 35 measures none of them. What it does measure, and what the extras cost, is in the [Check-up 35 guide](/en/guide/check-up-35-blutwerte).

About money, up front: we sell neither lab tests nor supplements and earn no commission on panels. The 'optimal' targets below come from guidelines and peer-reviewed research, not from a lab's upsell page. Want to know which of these markers your insurer covers when there is a medical reason, and what you pay yourself? See the guide on [statutory cover vs. self-pay](/en/guide/biologischer-alterstest-krankenkasse) and the [self-pay longevity guide](/en/guide/selbstzahler-longevity).

- A lab reference range is the central 95% of a population, not a health-optimized target: 'normal' and 'optimal' often come apart.
- Only glucose, fasting insulin and HOMA-IR strictly need a fast (at least 8 hours); the other six markers do not [1][6].
- hs-CRP and ferritin are acute-phase reactants: do not test within 2 to 3 weeks of infection, surgery or vaccination, or they are useless [2][12].
- We sell neither tests nor supplements: the optimal targets come from guidelines and studies, not from a lab upsell.
- The two most causal lipid markers, ApoB and Lp(a), we cover in the sister guide, not here.

## HOMA-IR and fasting insulin: How do I catch insulin resistance before blood sugar slips?

HOMA-IR is a simple calculation from fasting insulin and fasting glucose that estimates how insulin-resistant your metabolism is, meaning how poorly your cells still respond to the hormone insulin. The catch: insulin resistance often builds for years before fasting glucose or HbA1c leave the normal range. In the Whitehall II study, insulin sensitivity fell steeply about 5 years before a diabetes diagnosis, while fasting glucose only jumped in the last 3. [31] That is the entire point of measuring early.

The formula comes from the original HOMA paper by Matthews et al. 1985: HOMA-IR = fasting insulin (micro-units per mL) times fasting glucose (mg/dL) divided by 405. The SI variant is insulin times glucose (mmol/L) divided by 22.5. [1] You do not have to do the math yourself: drop your lab values into our [HOMA-IR calculator](/en/tools/homa-ir), which handles both unit systems automatically and interprets the result.

There is no single cutoff that works worldwide. Thresholds depend on population, ethnicity, age and lab assay, and usually land between 2.0 and 2.9. So instead of importing a US or Asian value, use German data. The population-based Gutenberg Health Study looked at 1,065 strictly healthy adults aged 35 to 74. Their median HOMA-IR (the middle value) was 1.09, and the middle half sat between 0.85 and 1.42 (the IQR). Only 2.5% were above 2.35 (the 97.5th percentile). So the statistical upper limit of 'normal' in healthy Germans is around 2.35. [3] That number is tied to the insulin test the study used. Other lab assays can read systematically higher or lower. [3]

The optimal longevity window is best read from the median: a healthy median near 1.0 (German data: 1.09) supports the often-cited 'optimal around below 1.0 to 1.5'. One caveat: 'below 1.0' is a wellness target. It is not a clinical cutoff tested against hard endpoints like heart attacks or death. [3] HOMA-IR still deserves attention. A meta-analysis of non-diabetic adults compared the highest with the lowest HOMA-IR category [4]:

- All-cause mortality: 34% higher (RR 1.34, 95% CI 1.11 to 1.62)
- Cardiovascular mortality: roughly 2.1-fold higher (RR 2.11, 95% CI 1.01 to 4.41). This figure comes from only two studies, so treat it as shaky.

RR is the relative risk. The 95% CI (confidence interval) is the range the true value most likely sits in. Both figures are associations from observational cohorts, not proof that lowering HOMA-IR extends life. [4]

Now an important caveat about fasting insulin on its own: the usual lab reference range of about 2.6 to 24.9 micro-units per mL is very wide, and metabolic-health literature cites an optimal window of roughly 2 to 6. But that '2 to 6' is wellness consensus with no backing from outcome trials at all. The meta-analysis above concludes that the mortality association holds for HOMA-IR, not for fasting insulin in isolation. So read '2 to 6' as an aspirational metabolic target, not a proven value. [4] Conversion: 1 micro-unit per mL is about 6.0 pmol/L, so 2 to 6 lands at roughly 12 to 36 pmol/L.

HbA1c and HOMA-IR are the metabolic pair you read together: HOMA-IR flags early insulin resistance, while [HbA1c](#hba1c) shows whether blood sugar has already caught up.

- HOMA-IR = fasting insulin x fasting glucose / 405 (mg/dL) or / 22.5 (mmol/L), from the original Matthews paper 1985 [1].
- There is no universal cutoff; in the German Gutenberg study the median in healthy adults was 1.09, the 97.5th percentile 2.35, and the values depend on the lab's insulin assay [3].
- A higher HOMA-IR was tied to 34% higher all-cause (RR 1.34) and roughly 2.1-fold higher cardiovascular mortality (RR 2.11, from only two studies) in a non-diabetic meta-analysis [4].
- The 'fasting insulin 2 to 6' target has NO outcome-trial backing: the mortality signal is for HOMA-IR, not insulin alone [4].
- Insulin resistance builds years before fasting glucose and HbA1c leave the normal range: in Whitehall II, insulin sensitivity fell steeply about 5 years before diagnosis [31].

## Hs-CRP: What level is good, and what does a high value mean?

hs-CRP (high-sensitivity C-reactive protein) is an inflammation marker in your blood. It picks up the low-grade background inflammation that tracks with atherosclerosis, the slow build-up of plaque in your arteries. For heart risk, the AHA/CDC consensus sorts it into three bands [2]:

- Below 1 mg/L: low risk
- 1 to 3 mg/L: average risk
- Above 3 mg/L: high risk

It is the same molecule as standard CRP. The high-sensitivity test can also resolve the low range below 10 mg/L, which is exactly the window that matters for heart risk. [2]

The longevity-optimal target is below 1 mg/L, which is directly the AHA/CDC 'low risk' band. Some practitioners aim for below 0.5 mg/L. The difference matters: below 1 is guideline-backed. Below 0.5 is a tighter wellness threshold that is not in the AHA/CDC statement. [2]

A value above 10 mg/L almost always means an acute phase, a running infection or inflammation. For heart risk it is then worthless; the consensus advises discarding it and retesting when you are well again. If the value stays high, it is worth searching for a non-cardiac source of inflammation. [2]

What else skews hs-CRP: infection, recent injury or surgery, vaccination and active inflammatory disease push it up for days to weeks. Obesity and smoking also raise the baseline, so interpret with care. [2]

hs-CRP and [ferritin](#ferritin) are the acute-phase pair you always read together: if both are high at the same time, inflammation is often behind it rather than the value you actually set out to measure.

- AHA/CDC risk strata: below 1 mg/L low, 1 to 3 average, above 3 high cardiovascular risk [2].
- Longevity-optimal is below 1 mg/L (guideline-backed); the below 0.5 some cite is a wellness threshold, not an AHA/CDC value [2].
- Above 10 mg/L means an acute phase: for heart risk, discard and retest when you are well [2].
- Infection, surgery, vaccination, active inflammation, obesity and smoking raise hs-CRP, so read it with care [2].
- hs-CRP measures the same molecule as standard CRP, just with an assay that resolves the heart-relevant range below 10 mg/L [2].

## High homocysteine: Is lowering it with folate and B vitamins worth it?

The short version: B vitamins reliably lower homocysteine by around 25%. But three large heart and stroke trials and a meta-analysis of 8 trials with 37,485 people show that this lowering did not reliably cut heart attacks. Treat homocysteine as a risk marker and a clue to your B-vitamin status, not as a proven drug target. [7][8][9][11]

Homocysteine is an amino acid that climbs when folate, vitamin B12 or B6 run low or methylation (a central metabolic pathway) stalls. The usual upper lab limit is about 15 micromol per liter (often around 13 for women, 15 for men). Hyperhomocysteinemia is classically defined above 15. [6] As a practical optimum, below 7 to 10 is often cited; risk appears to rise continuously from about 6 to 7 upward, well below the lab limit. Here too: 'below 10' is a practitioner target, not a hard guideline cutoff, and the exact value depends on method and population. [6]

That B vitamins work is not in dispute: folate, B12 and B6 typically lower homocysteine by about 25%. [7][8][11] The catch: this lowering did not reliably reduce cardiovascular events. Here are the trials that show it:

- The HOPE-2 trial (NEJM 2006) gave 5,522 high-risk patients folic acid 2.5 mg plus B6 50 mg plus B12 1 mg. Homocysteine fell, but the primary composite of cardiovascular death, heart attack and stroke did not (RR 0.95, 95% CI 0.84 to 1.07). Only stroke showed a modest signal (RR 0.75, 95% CI 0.59 to 0.97). More people on the vitamins were hospitalized for unstable angina (RR 1.24). [7]
- The NORVIT trial (NEJM 2006) treated 3,749 patients after a heart attack. No benefit (primary RR 1.08, not significant), and the triple-combination arm even trended toward harm (RR 1.22, P=0.05). The authors advised against routine use after a heart attack. [8]
- The VITATOPS trial (Lancet Neurol 2010) gave 8,164 patients after stroke or TIA B vitamins. Homocysteine fell, but major vascular events did not drop significantly (RR 0.91, P=0.05, not significant). [9]
- The B-PROOF trial (Am J Clin Nutr 2014) tested fractures, not the heart, but it adds a safety signal. It gave older people with high homocysteine folic acid 400 micrograms plus B12 500 micrograms. No significant effect on fractures, and an unexpected rise in cancer incidence in the treatment arm. The authors could not recommend it. [10]
- The Clarke et al. 2010 meta-analysis pooled 8 randomized trials with 37,485 people. Despite a roughly 25% homocysteine reduction, no significant effect on major vascular events (RR 1.01), coronary events (1.03), stroke (0.96), cancer or all-cause mortality (1.02). All null. [11]

The reading: the only residual signal is a small, inconsistent stroke effect (and even VITATOPS was not significant here, at P=0.05). Everything else is null, with three harm signals (the NORVIT combination, unstable angina in HOPE-2, the B-PROOF cancer signal). High homocysteine is a clue to check your B-vitamin and methylation status, not a promise that 'lowering it' prevents heart attacks. What you actually do is best discussed with your GP.

- B vitamins (folate, B12, B6) reliably lower homocysteine by around 25% [7][8][11].
- HOPE-2 (NEJM 2006, 5,522 patients): no effect on the primary cardiovascular endpoint (RR 0.95), only a stroke signal (RR 0.75) [7].
- NORVIT (NEJM 2006, 3,749 patients): no benefit and a harm trend in the triple combination (RR 1.22, P=0.05) [8].
- Clarke meta-analysis 2010 (8 trials, 37,485 people): despite 25% lowering, all endpoints null, all-cause mortality RR 1.02 [11].
- B-PROOF (2014), a fracture trial, showed an unexpected cancer signal in the B-vitamin arm: lowering homocysteine is NOT proven heart protection [10].

## HbA1c: When is it prediabetes, and which value is really optimal?

HbA1c is your long-term blood sugar: the share of your hemoglobin (the oxygen carrier in red blood cells) with sugar stuck to it, averaged over about three months. It is the counterpart to HOMA-IR and shows whether blood sugar has already caught up. The ADA 2026 cutoffs [5]:

- Normal: below 5.7% (below 39 mmol/mol)
- Prediabetes: 5.7 to 6.4% (39 to 47 mmol/mol)
- Diabetes: at or above 6.5% (at or above 48 mmol/mol), confirmed on a second test

The WHO confirmed the same diagnostic threshold of 6.5% (48 mmol/mol) for diabetes in 2011, but notes that a value below 6.5 does not rule out diabetes diagnosed via glucose. [14] The German DDG/DGKL practice recommendation (2022 update) uses the same anchors: HbA1c at or above 48 mmol/mol (6.5%) and fasting glucose at or above 126 mg/dL (7.0 mmol/L). [15]

German lab reports give HbA1c in two units, and they get muddled. NGSP is the percent value. IFCC is the value in mmol/mol. The master formula: NGSP (%) = 0.09148 x IFCC + 2.152 (commonly rounded to 0.0915 x IFCC + 2.15). So 5.7% is about 39, 6.0% about 42 and 6.5% about 48 mmol/mol. [16][32]

What is optimal? Below 5.4 to 5.6% is often named as the optimum. That sits below the prediabetes line of 5.7. One distinction: the '5.4' is a wellness optimum. The guideline ceiling of 'normal' is 5.6% (below 5.7). [5] The best outcome data come from a large US cohort (ARIC). There, an HbA1c of 5.0 to 5.5% went with low diabetes and heart risk. For death from any cause the curve was J-shaped, so very low values were not better. [29]

And now the most important trap: HbA1c is distorted by your red-cell turnover. Iron deficiency (with or without anemia) falsely raises the measured HbA1c without any rise in your actual blood sugar. Conversely, non-iron-deficiency anemia, hemolysis (breakdown of red cells), recent blood loss and many hemoglobinopathies lower it. The systematic review by English et al. 2015 (Diabetologia) confirms the direction: iron deficiency upward, non-iron-deficiency anemia downward. So read a borderline-high HbA1c in someone with low [ferritin](#ferritin) with caution, it may be an artefact. Always read HbA1c alongside ferritin and a blood count. [13]

- ADA 2026: HbA1c normal below 5.7% (below 39 mmol/mol), prediabetes 5.7 to 6.4 (39 to 47), diabetes at or above 6.5 (at or above 48) [5].
- WHO 2011 and the German DDG/DGKL recommendation 2022 use the same diabetes cutoff of 6.5% (48 mmol/mol) [14][15].
- Conversion: NGSP-% = 0.09148 x IFCC + 2.152, which makes 6.5% equal to 48 mmol/mol [16][32].
- The often-cited optimum below 5.4 to 5.6% is partly a wellness target; the guideline ceiling of 'normal' is 5.6% [5], and very low values did not lower mortality further (J-curve) [29].
- Iron deficiency FALSELY RAISES the measured HbA1c, so always read HbA1c alongside ferritin and a blood count [13].

## Omega-3 Index: What is a good level, and what if yours is low?

The Omega-3 Index is the share of EPA and DHA (the two marine omega-3 fatty acids) in the membrane of your red blood cells, expressed as a percentage. It is a status marker and reflects about 120 days of intake, a stable weeks-to-months average, unlike the swinging plasma fatty acids. You do not need to fast for it. [17]

The index goes back to a 2004 paper by Harris and von Schacky (Prev Med). They proposed it as a risk factor for death from coronary heart disease that works on a sliding scale: the higher the index, the lower the risk. At or above 8%, protection was greatest, so 8% is the desirable target. At 4% or below, protection was lowest, which counts as high risk. The often-quoted 'intermediate' band of 4 to 8% is simply the stretch of the same curve in between. So read the index as a sliding scale, not three rigid boxes. [17]

The optimal range quoted most often is 8 to 12%. The 8% target comes from the 2004 paper. [17] The upper bound is a later convention: von Schacky proposes 8 to 11% [30], and some labs quote 8 to 12%. A 2007 review by the same two authors described the risk of sudden cardiac death climbing steeply as the index fell from 6.5% to 3.3%. [18]

Capsules are a different story: the trial evidence for omega-3 supplements is mixed. The REDUCE-IT trial (NEJM 2019) gave statin-treated patients with high triglycerides high-dose, purified EPA (icosapent ethyl, 4 g per day). Major cardiovascular events fell by around 25% (HR 0.75, 95% CI 0.68 to 0.83). But the placebo was mineral oil, and it raised LDL and hs-CRP in the comparison group, which makes the benefit contested. [19] The STRENGTH trial (JAMA 2020), using an EPA-plus-DHA formulation, found no cardiovascular benefit at all (HR 0.99). It was stopped early because a benefit had become very unlikely (futility). [20] The VITAL trial (NEJM 2019) gave 1 g of marine omega-3 per day to a general population not selected for low intake. It did not lower the primary cardiovascular and cancer endpoints (HR 0.92 and 1.03). A secondary endpoint, heart attacks alone, was lower (HR 0.72), but that was not the main test. [26]

The consequence: the index measures your status cleanly, but raising it with capsules has not consistently led to fewer events. The first lever is diet, meaning oily sea fish. Want to see how a meal affects your own metabolism? The [glucose and blood sugar guide](/en/guide/glukose-blutzucker-hacks) shows how, using glucose.

- The Omega-3 Index = EPA + DHA as a percentage of red-blood-cell fatty acids, a 120-day status marker, no fasting needed [17].
- Harris and von Schacky 2004: at or above 8% greatest protection, at 4% or below high risk, as a graded continuum [17].
- Optimal range usually 8 to 12%, with below 4% counting as high risk; the 8% target is from the 2004 paper [17], the upper bound a later convention (von Schacky: 8 to 11%) [30].
- REDUCE-IT (2019) cut events by 25% (HR 0.75), but the mineral-oil placebo makes the finding contested [19].
- STRENGTH (HR 0.99) and VITAL missed their primary endpoints: raising the index with capsules did not consistently cut events, diet first [20][26].

## Ferritin and iron deficiency: Why 'within range' can still mean a deficiency

Ferritin reflects your iron stores, but it is also an acute-phase reactant: an infection or inflammation falsely raises it, independent of your actual iron status. So always read ferritin alongside [hs-CRP](#hs-crp). [12]

The WHO 2020 thresholds for iron deficiency [12]:

- Apparently healthy people 5 and older (including non-pregnant women and adults): ferritin below 15 micrograms per liter
- Apparently healthy children under 5: below 12
- With infection or inflammation at the same time: below 70 (5 and older) and below 30 (children under 5)

In practice, many clinicians use below 30 micrograms per liter as the deficiency cutoff in adults. It catches more real cases than below 15 (it is more sensitive). Below 15 is rarely wrong when it flags a deficiency (highly specific), but it misses many. For ferritin, ng/mL and micrograms per liter are the same number: 1 ng/mL = 1 microgram per liter.

This is exactly where the headline example of 'normal is not optimal' sits. Iron deficiency can cause fatigue even without anemia. [12] Practitioners often link fatigue and hair loss to 'low-normal' ferritin of about 15 to 50 micrograms per liter, in the middle of the lab normal range. Those thresholds come from practitioner literature, not from a guideline, so treat them as a clue, not a settled cutoff. One threshold does have a guideline now. If you have diagnosed restless legs, the US sleep society (AASM) recommends iron at a ferritin of 75 or lower, or a transferrin saturation below 20%. [27]

And more is not better: ferritin above 150 (women) or above 200 (men) in apparently healthy people, or above 500 in non-healthy individuals, can flag iron overload or disease. [12] Whether a low or a high value needs to be worked up in your case belongs in the hands of your GP.

- WHO 2020 (healthy): iron deficiency from a ferritin below 15 micrograms per liter (5 and older), below 12 in children under 5 [12].
- With inflammation the higher cutoffs apply: below 30 (children under 5) and below 70 (5 and older) [12].
- Iron deficiency can cause fatigue without anemia [12]; for diagnosed restless legs the AASM gives iron at a ferritin of 75 or lower [27].
- More is not better: above 150 (women) or above 200 (men) can flag iron overload [12].
- Ferritin is an acute-phase reactant and must be read alongside hs-CRP; 1 ng/mL = 1 microgram per liter [12].

## Vitamin D: Deficiency, optimum, and what the big VITAL trial actually showed

25-OH-D is the storage form of vitamin D in your blood. Two threshold systems are in use, and they disagree.

The older Endocrine Society 2011 thresholds [22]:

- Deficiency: below 20 ng/mL (below 50 nmol/L)
- Insufficiency: 20 to below 30 ng/mL (50 to below 75 nmol/L)
- Sufficient: at or above 30 ng/mL (at or above 75 nmol/L)

The US Institute of Medicine (IOM), by contrast, considered 20 ng/mL (50 nmol/L) already enough for bone health. [22] The Endocrine Society's own 2024 update no longer names a target level: it found no clear evidence for any optimal 25-OH-D level to prevent disease. [23]

The German line used by the RKI [24]:

- Deficient: below 30 nmol/L (below 12 ng/mL)
- Suboptimal: 30 to below 50 nmol/L (12 to below 20 ng/mL)
- Adequate for bone health: at or above 50 nmol/L (at or above 20 ng/mL)

In the RKI survey DEGS1, about 62% of German adults sat below 50 nmol/L. The RKI uses 50 nmol/L as the common threshold. [24] Many longevity practitioners aim for 30 to 50 ng/mL (75 to 125 nmol/L). That is a higher target than the 20 ng/mL considered adequate for bone health at population level. It is not a longevity value validated against endpoints. [22]

The most important result comes from the VITAL trial (NEJM 2019). It gave 25,871 US adults, most of whom already had enough vitamin D, vitamin D3 at 2000 IU per day for about five years. It lowered neither cancer (HR 0.96) nor major cardiovascular events (HR 0.97) versus placebo. [21] Consequently the 2024 Endocrine Society guideline advises against routine 25-OH-D testing. That holds for healthy adults and even for the groups where it suggests taking vitamin D anyway (such as 75 and older, pregnancy, prediabetes, under-18s). It calls this empiric supplementation, meaning without prior testing. [23]

The reading: correct a genuine deficiency (bone, fall risk), but do not sell vitamin D as a heart or cancer prevention drug for people who are already replete. And more is not better here either. A 25-OH-D above 150 ng/mL (above 375 nmol/L) is the hallmark of vitamin D intoxication with hypercalcemia (too much calcium in the blood). The IOM also flagged possible harm from long-term levels above 50 ng/mL, based on association studies. [25] If you want to supplement vitamin D, discuss dose and monitoring with your doctor. For how epigenetic age tests differ from single biomarkers like these, see the guide on [epigenetic age tests](/en/guide/epigenetic-tests).

- Older Endocrine Society 2011 thresholds: 25-OH-D below 20 ng/mL (below 50 nmol/L) deficient, 20 to 30 insufficient, at or above 30 sufficient [22].
- RKI: at or above 50 nmol/L (20 ng/mL) adequate for bone health; about 62% of German adults sit below that (DEGS1) [24].
- VITAL (NEJM 2019, n=25,871): 2000 IU/day lowered neither cancer (HR 0.96) nor cardiovascular events (HR 0.97) [21].
- The 2024 Endocrine Society guideline names no target level and advises against routine 25-OH-D testing, even in the groups it suggests supplementing [23].
- More is not better: above 150 ng/mL (375 nmol/L) is the hallmark of vitamin D intoxication [25].

## Longevity blood test optimal ranges: Table of all 8 markers

Here is everything in one table: on the left the standard lab reference range (in conventional and SI units), in the middle the tighter 'optimal' longevity window cited in the literature, on the right the sources. Read the optimal column as aspirational, not as a diagnosis: several of these tighter targets are practitioner or wellness goals, not guideline cutoffs validated against hard endpoints.

| Marker | Standard / lab reference (conventional and SI) | Optimal longevity target | Sources |
|---|---|---|---|
| HOMA-IR | healthy 97.5th pct up to 2.35 (unitless, assay-dependent); IR cutoffs ~2.0 to 2.9 (population-dependent) | ~below 1.0 to 1.5 (healthy median ~1.09) | [1][3][4] |
| Fasting insulin | ~2.6 to 24.9 micro-U/mL; ~16 to 150 pmol/L | ~2 to 6 micro-U/mL; ~12 to 36 pmol/L (wellness target, NO outcome-trial backing, the mortality signal is for HOMA-IR) | wellness consensus |
| hs-CRP | below 1 low / 1 to 3 average / above 3 high mg/L; above 10 = acute | below 1 mg/L (guideline); some aim for below 0.5 (not guideline) | [2] |
| Homocysteine | upper limit ~15 micromol/L (~13 women / 15 men) | below 7 to 10 micromol/L (practitioner target; lowering NOT proven as heart protection) | [6][7][11] |
| HbA1c | normal below 5.7% (below 39 mmol/mol); preDM 5.7 to 6.4 (39 to 47); DM at or above 6.5 (at or above 48) | below 5.4 to 5.6% (below 5.4 is a wellness target; very low values not better for mortality) | [5][14][16][29] |
| Omega-3 Index | below 4% high risk / 4 to 8% intermediate / at or above 8% desirable (continuum) | 8 to 11% (von Schacky) or 8 to 12% (some labs), RBC EPA+DHA; 8% target from [17], upper bound a later convention [30] | [17][18][30] |
| Ferritin | deficiency below 15 micrograms/L (5 and older, healthy); below 30/70 with inflammation; overload above 150 women / 200 men | ~30 to ~150 micrograms/L comfort window (symptoms possible below 50, practitioner level; iron for diagnosed restless legs at 75 or lower, AASM); 1 ng/mL = 1 microgram/L | [12][27] |
| Vitamin D (25-OH-D) | deficient below 20 ng/mL (below 50 nmol/L); insufficient 20 to 30 (50 to 75); sufficient at or above 30 (ES 2011, no target named in 2024) / at or above 20 (IOM/RKI) | 30 to 50 ng/mL; 75 to 125 nmol/L (practitioner; toxicity above 150 ng/mL) | [22][23][24][25] |
| ApoB / Lp(a) | in the sister lipid guide | see link below | (sister guide) |

Two things to take away. First: the two most causal lipid markers are missing here on purpose. [ApoB and Lp(a)](/en/guide/apob-lpa) we cover in the sister guide, because they deserve their own depth. Second: 'normal' is the start, not the goal, but do not overclaim the optimum. Where the evidence is thin (fasting insulin, hs-CRP below 0.5, HbA1c below 5.4, ferritin symptom thresholds), we flagged it openly above. And we still sell neither tests nor supplements: these targets come from the literature, not from a product catalogue.

- The table sets each marker's lab reference next to its tighter optimal window, with sources [1][2][5][12][22].
- Several optimal values are practitioner targets with no endpoint validation, above all fasting insulin and hs-CRP below 0.5 [4][2].
- ApoB and Lp(a) are missing on purpose and are covered in depth in the sister lipid guide.
- More is not better for ferritin and vitamin D: overload and toxicity have their own upper limits [12][25].
- The targets come from guidelines and studies, not a product catalogue; we sell nothing.


## FAQ

### Which blood values should I test for longevity?

Eight markers cover most of it: fasting insulin, HOMA-IR, hs-CRP, homocysteine, HbA1c, the Omega-3 Index, ferritin and vitamin D (25-OH-D). The two most causal lipid markers, ApoB and Lp(a), come on top in the sister guide. Only glucose, fasting insulin and the HOMA-IR computed from them need a fast of at least 8 hours [1].

### How much does a longevity blood test cost?

In Germany the eight markers in this guide cost roughly 170 to 290 euros as a self-pay service (IGeL), including 10 to 20 euros for the blood draw. Typical ranges per marker: HbA1c 13 to 20, fasting insulin 15 to 25, hs-CRP 13 to 25, ferritin 15 to 25, homocysteine and vitamin D 30 to 45 each, Omega-3 Index 40 to 80 euros. Skip homocysteine and vitamin D, the two with the thinnest evidence, and you land near 110 to 200 euros. Per-marker prices for all but the Omega-3 Index are in the [Check-up 35 guide](/en/guide/check-up-35-blutwerte).

### Do I need to fast for a longevity blood test?

Only for part of it. Glucose, fasting insulin and the HOMA-IR calculated from them need at least 8 hours without food, because the HOMA formula is built on fasting values [1]. HbA1c, hs-CRP, ferritin, the Omega-3 Index and vitamin D work without fasting. Homocysteine is usually reported fasting, but a non-fasting sample is fine for screening [6]. Do not test hs-CRP or ferritin within two to three weeks of an infection, or they read falsely high [2][12].

### Why is my blood value 'normal' but still not optimal?

Because a lab reference range is defined statistically, as the central 95% of a reference population. It tells you whether you fall into the middle of the distribution, not whether your value carries the lowest risk of disease and death. The best example is ferritin. Iron deficiency can cause fatigue even without anemia [12], and practitioners often see complaints at 'low-normal' values of 15 to 50 micrograms per liter, in the middle of the normal range. For diagnosed restless legs, the US sleep society AASM recommends iron at a ferritin of 75 or lower [27].

### At what HbA1c do I have prediabetes?

By the ADA 2026 cutoffs, prediabetes starts at an HbA1c of 5.7 to 6.4% (39 to 47 mmol/mol); at or above 6.5% (48 mmol/mol) counts as diabetes, confirmed on a second test [5]. The WHO and the German DDG/DGKL recommendation use the same diabetes cutoff of 6.5% [14][15]. But iron deficiency can falsely raise the measured HbA1c, so always read it alongside ferritin [13].

### Is it worth lowering high homocysteine with B vitamins?

B vitamins reliably lower homocysteine by around 25%, but large trials and a meta-analysis of 8 trials with 37,485 people (Clarke 2010) show this lowering did not reliably cut heart attacks (all-cause mortality RR 1.02) [7][11]. The only residual signal is a small, inconsistent stroke effect. There were also harm signals: the NORVIT combination, more unstable angina in HOPE-2 and a cancer signal in B-PROOF [7][8][10]. Treat homocysteine as a clue to your B-vitamin status and discuss any consequences with your GP.

### What is a good Omega-3 Index?

The Omega-3 Index measures EPA and DHA as a percentage of your red-blood-cell fatty acids; at or above 8% counts as the greatest protection per Harris and von Schacky 2004, with below 4% high risk [17]. As an optimal range, 8 to 12% is usually cited. The upper bound is a later convention, not from that 2004 paper: von Schacky himself proposes 8 to 11% [30]. Raising the index with capsules, though, did not consistently cut events in trials like STRENGTH (HR 0.99) and VITAL, so go to diet first with oily sea fish [20][26].

### My Omega-3 Index is low. What should I do?

Below 4% counts as high risk, 8% or more as the desirable target [17]. The first lever is diet: oily sea fish such as salmon, mackerel or herring. Capsules can lift the number, but in trials that did not reliably cut heart events: STRENGTH was null (HR 0.99) and VITAL missed its primary endpoint at 1 g a day [20][26]. Because the index tracks about 120 days, retest no sooner than three to four months after a change [17].

### Is an hs-CRP value below 1 mg/L good?

Yes, below 1 mg/L is the 'low risk' band of the AHA/CDC consensus, 1 to 3 is average and above 3 is high cardiovascular risk [2]. A value above 10 mg/L usually means an acute infection and is worthless for heart risk, so retest when you are well again [2]. The below 0.5 some cite is a tighter wellness threshold, not an AHA/CDC value.

### At what ferritin do I have iron deficiency?

By the WHO 2020, iron deficiency in apparently healthy people 5 and older sits at a ferritin below 15 micrograms per liter; with concurrent inflammation, below 70 applies [12]. Clinically, many use below 30 as the practical cutoff in adults. Because ferritin is an acute-phase reactant, read it alongside hs-CRP. Inflammation can push a low value up into the normal range and hide a real deficiency [12].

### Should I test vitamin D, and at what value is it a deficiency?

By the older 2011 Endocrine Society thresholds, deficiency sits below 20 ng/mL (below 50 nmol/L), while the German line used by the RKI considers 50 nmol/L enough for bone health [22][24]. But the VITAL trial showed that 2000 IU per day in replete adults lowered neither cancer (HR 0.96) nor heart events (HR 0.97), which is why the 2024 Endocrine Society guideline advises against routine screening in healthy people [21][23]. Test if there is a risk or a suspected deficiency, and correct a genuine deficiency with your doctor.

### Does statutory insurance cover a longevity blood test?

Usually not: without a documented medical indication, most of these markers run as an IGeL (Individuelle Gesundheitsleistung), the German term for a self-pay service. HbA1c, ferritin and vitamin D are covered by statutory insurance only with a concrete indication (such as suspected diabetes, documented deficiency symptoms, osteoporosis); pure longevity screening in healthy people is self-pay. For vitamin D, the IGeL-Monitor of the Medizinischer Dienst says it directly: screening people without symptoms is IGeL, at roughly 28 to 32 euros in lab fees plus the draw [28]. What the statutory Check-up 35 already measures is in the [Check-up 35 guide](/en/guide/check-up-35-blutwerte); what the rest costs privately is in the guide on [statutory cover vs. self-pay](/en/guide/biologischer-alterstest-krankenkasse).

### How often should I repeat a longevity blood test?

No guideline sets a retest interval for healthy people, so let biology set the pace. HbA1c reflects about three months of blood sugar and the Omega-3 Index about 120 days of intake [17], so retesting sooner after a change tells you little. A sensible rhythm: one baseline, a recheck three to four months after any change in diet or supplements, then roughly once a year while everything sits in range.

## Sources

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_Full guide: https://longevity-germany.com/en/guide/longevity-bluttest-biomarker_

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