Blood Tests to Ask Your GP For: A Longevity Panel Guide
Most NHS blood tests are designed to diagnose disease — not to catch the slow, silent decline in biomarkers that precedes it by years or decades. A proactive longevity panel works differently: it tracks the markers that predict long-term health trajectory before anything goes clinically wrong.
This guide covers exactly which blood tests to request, what optimal ranges look like (not just "normal"), which tests your GP can order on the NHS, and which require private testing if you want the full picture.
What Is a Longevity Blood Panel?
A longevity blood panel is a set of blood tests that measures metabolic health, inflammation, cardiovascular risk, hormonal ageing, and organ function — chosen not just to rule out disease, but to track biological ageing and identify areas for targeted intervention.
Standard NHS health checks typically cover full blood count, basic metabolic panel, cholesterol, and HbA1c. These are useful baselines but fall short of what's needed to proactively manage healthspan. A longevity-oriented panel extends this to include inflammatory markers, insulin dynamics, hormonal ageing indicators, and nutrient status — several of which require either a specific GP request or private testing.
The distinction that matters most is between reference ranges and optimal ranges. NHS reference ranges define the boundary between sick and not-sick. Longevity research defines a narrower zone where risk of age-related disease and biological ageing is meaningfully lower. The two are not the same.
The Core Panel: What to Ask Your GP For on the NHS
The following tests can generally be requested through your GP, though availability varies by practice and clinical indication. The most effective approach is to frame the request around proactive cardiovascular and metabolic health monitoring — GPs are more likely to authorise tests within that framing than under a general "longevity" request.
1. HbA1c (Glycated Haemoglobin)
What it measures: Average blood glucose over the preceding 8–12 weeks, expressed as a percentage of haemoglobin molecules with glucose attached.
Why it matters for longevity: Elevated HbA1c — even within the "normal" NHS range — is one of the strongest independent predictors of cardiovascular disease, cognitive decline, and all-cause mortality. The glycation process that HbA1c reflects (glucose molecules binding to proteins) is a core mechanism of biological ageing, driving cross-linking of collagen, lens proteins, and blood vessel walls.
| Range | Classification |
|---|---|
| Below 39 mmol/mol (5.7%) | Optimal for longevity |
| 39–47 mmol/mol (5.7–6.4%) | Pre-diabetic / elevated risk |
| 48 mmol/mol+ (6.5%+) | Diabetic range |
Longevity note: The NHS "normal" upper limit is 47 mmol/mol. Longevity-focused clinicians typically target below 39 mmol/mol (below 5.7%) as the zone of lowest long-term risk.
2. Fasting Glucose and Fasting Insulin
What it measures: Blood glucose after an 8–12 hour fast. Fasting insulin measures the hormonal response required to maintain that glucose level.
Why it matters for longevity: Fasting glucose alone misses early insulin resistance — a metabolic state that can persist for a decade before glucose levels become visibly elevated. Fasting insulin is a more sensitive early marker. The HOMA-IR score (Homeostatic Model Assessment of Insulin Resistance) can be calculated from both values: HOMA-IR = (fasting glucose mmol/L × fasting insulin mU/L) ÷ 22.5.
| HOMA-IR Score | Interpretation |
|---|---|
| Below 1.0 | Optimal insulin sensitivity |
| 1.0–1.9 | Mildly elevated — monitor |
| 2.0–2.9 | Insulin resistant |
| 3.0+ | Significantly insulin resistant |
GP request note: Fasting insulin is not routinely offered on the NHS but can often be requested. Frame it as assessing insulin resistance risk given family history or metabolic health concerns. Many GPs will oblige. If not, it is inexpensive as a private test (typically £20–35).
3. Full Lipid Panel + ApoB
What it measures: Total cholesterol, LDL-C, HDL-C, triglycerides — and ideally Apolipoprotein B (ApoB).
Why ApoB matters more than LDL-C: LDL-C measures the cholesterol content of LDL particles. ApoB measures the actual number of atherogenic particles (one ApoB protein per LDL, VLDL, and IDL particle). Particle number is a stronger predictor of cardiovascular risk than cholesterol concentration — particularly in people with metabolic syndrome, where LDL-C can appear normal while ApoB is elevated.
Data from the INTERHEART study and multiple prospective cohorts consistently demonstrate that ApoB outperforms LDL-C as a cardiovascular mortality predictor.
| Marker | Optimal (Longevity) | NHS Standard Reference |
|---|---|---|
| LDL-C | Below 2.0 mmol/L | Below 3.0 mmol/L |
| HDL-C | Above 1.5 mmol/L (men), above 1.8 mmol/L (women) | Above 1.0 mmol/L (men) |
| Triglycerides | Below 1.0 mmol/L | Below 1.7 mmol/L |
| ApoB | Below 0.7 g/L | Varies; often not routinely reported |
GP request note: Standard lipid panels are routinely available. ApoB requires a specific request — some NHS labs offer it, others do not. Worth asking explicitly. Alternatively available privately for around £25–40.
4. hs-CRP (High-Sensitivity C-Reactive Protein)
What it measures: A highly sensitive measure of systemic inflammation, specifically detecting low-grade chronic inflammation that standard CRP tests miss.
Why it matters for longevity: Chronic low-grade inflammation — "inflammageing" — is one of the most robustly evidenced biological mechanisms of accelerated ageing. hs-CRP is among the best accessible blood-based proxies for this process. Elevated hs-CRP is an independent predictor of cardiovascular disease, cancer risk, cognitive decline, and all-cause mortality.
| hs-CRP Level | Cardiovascular Risk / Longevity Interpretation |
|---|---|
| Below 0.5 mg/L | Optimal |
| 0.5–1.0 mg/L | Low risk |
| 1.0–3.0 mg/L | Moderate risk — investigate |
| Above 3.0 mg/L | High risk — action required |
GP request note: Standard CRP is routinely available. High-sensitivity CRP (hs-CRP) requires a specific request — it uses a more sensitive assay and is available on the NHS, though some practices default to standard CRP unless asked. Be explicit: "I'd like high-sensitivity CRP specifically."
5. Homocysteine
What it measures: An amino acid produced during methionine metabolism. Elevated levels indicate impaired methylation — typically due to insufficient B12, folate, or B6.
Why it matters for longevity: Elevated homocysteine is an independent risk factor for cardiovascular disease, stroke, cognitive decline, and Alzheimer's disease. It damages arterial endothelium directly and promotes oxidative stress. Homocysteine also sits at the intersection of the methylation cycle — the same pathway through which TMG (trimethylglycine) and B vitamins support NMN metabolism, as covered in our article on how TMG supports NMN metabolism.
| Homocysteine Level | Interpretation |
|---|---|
| Below 7 µmol/L | Optimal |
| 7–10 µmol/L | Acceptable — monitor |
| 10–15 µmol/L | Mildly elevated — supplement B vitamins |
| Above 15 µmol/L | Elevated — clinical review warranted |
GP request note: Homocysteine is available on the NHS but is not routinely checked. Request it as part of cardiovascular risk assessment. If your GP declines, it is one of the most informative private tests available at low cost (£30–50).
6. Vitamin D (25-OH-D3)
What it measures: Serum 25-hydroxyvitamin D — the storage form of vitamin D and the correct marker of vitamin D status.
Why it matters for longevity: Vitamin D deficiency is associated with increased all-cause mortality, cardiovascular disease, autoimmune conditions, depression, and impaired immune function. In the UK, where dietary sources are limited and sunlight exposure insufficient for 6–8 months of the year, deficiency is extremely common — estimated to affect over 40% of adults by some measures.
| 25-OH-D3 Level | Interpretation |
|---|---|
| Below 30 nmol/L | Deficient |
| 30–50 nmol/L | Insufficient |
| 50–75 nmol/L | Adequate (NHS threshold) |
| 75–150 nmol/L | Optimal for longevity |
| Above 250 nmol/L | Potentially toxic — rare with supplementation |
GP request note: Vitamin D testing is available on the NHS, though in recent years many practices have restricted routine testing to symptomatic patients or high-risk groups. If declined, it is the single most cost-effective private test available — typically £25–30 — and arguably the highest-yield intervention available from a population-level perspective.
7. Full Blood Count (FBC) and Iron Studies (Including Ferritin)
What it measures: Red and white blood cell counts, haemoglobin, platelets; and separately, serum ferritin (the body's iron storage protein).
Why ferritin specifically matters for longevity: Ferritin is routinely used to detect iron deficiency anaemia. However, elevated ferritin is a less commonly discussed risk factor — excess iron catalyses the Fenton reaction, generating highly reactive hydroxyl radicals that cause oxidative damage to DNA and lipids. This is directly relevant to the ferroptosis mechanism discussed in our NAC and longevity article. High ferritin is also an inflammatory marker in its own right.
| Ferritin Level | Interpretation |
|---|---|
| Below 30 µg/L | Low — risk of iron deficiency |
| 30–100 µg/L | Optimal range |
| 100–200 µg/L | Acceptable — monitor dietary iron |
| Above 200 µg/L | Elevated — investigate cause |
GP request note: FBC is standard. Ferritin requires a specific request but is routinely available on the NHS.
8. Kidney Function: eGFR and Creatinine
What it measures: Estimated glomerular filtration rate — a calculation of how efficiently the kidneys filter waste from the blood, derived from serum creatinine, age, and sex.
Why it matters for longevity: eGFR is one of the cleaner functional proxies for biological age in the kidney — and kidney function is tightly correlated with all-cause mortality even in the "normal" range. An eGFR that is declining over successive tests — even within normal limits — is a meaningful signal worth tracking.
| eGFR (mL/min/1.73m²) | Kidney Function Stage |
|---|---|
| Above 90 | Normal (longevity optimal: above 90) |
| 60–89 | Mildly reduced — monitor |
| 45–59 | Moderately reduced — GP review |
| Below 45 | Clinically significant — specialist referral |
GP request note: eGFR is part of the standard renal function panel (U&Es) — routinely available.
9. Liver Function Tests (LFTs) Including GGT
What it measures: ALT, AST, ALP, bilirubin, albumin. Of particular longevity relevance: gamma-glutamyl transferase (GGT).
Why GGT matters beyond alcohol: GGT is commonly associated with alcohol use, but it is also a sensitive marker of oxidative stress and glutathione turnover. Elevated GGT in non-drinkers often reflects metabolic dysfunction, liver fat accumulation, or high oxidative burden — all relevant to ageing trajectories.
GP request note: LFTs are standard. GGT is typically included automatically.
10. Thyroid Function: TSH (and Free T3/T4 if indicated)
What it measures: TSH (thyroid-stimulating hormone) is the primary screening marker for thyroid dysfunction. Free T3 and T4 provide more detail if TSH is abnormal.
Why it matters for longevity: Thyroid hormones regulate metabolic rate, mitochondrial function, body composition, and cardiovascular health. Both hypothyroidism and subclinical hypothyroidism (normal T4, mildly elevated TSH) are associated with accelerated cardiovascular ageing and cognitive decline. Hyperthyroidism carries its own risks including atrial fibrillation and bone density loss.
| TSH Level | Interpretation |
|---|---|
| 0.5–2.0 mIU/L | Optimal |
| 2.0–4.0 mIU/L | Normal but worth monitoring over time |
| Above 4.0 mIU/L | Elevated — possible subclinical hypothyroidism |
GP request note: TSH is routinely available. Free T3 and free T4 are available on the NHS but often only requested if TSH is outside range.
The Extended Panel: High-Value Private Tests
The following are not routinely available on the NHS but represent the highest-yield additions to a longevity monitoring protocol. Most are available through private blood testing services (Medichecks, Thriva, Randox Health) at relatively low cost.
IGF-1 (Insulin-Like Growth Factor 1)
What it measures: A downstream mediator of growth hormone (GH) signalling, produced primarily in the liver.
Why it matters for longevity: IGF-1 occupies a unique and somewhat paradoxical position in longevity research. High IGF-1 in youth supports tissue repair and muscle mass. However, chronically elevated IGF-1 in mid-to-later life is associated with accelerated cellular growth signalling via the mTOR pathway — one of the central ageing mechanisms. Populations with naturally low IGF-1 (such as Laron syndrome patients with GH receptor deficiency) show markedly reduced rates of cancer and diabetes despite short stature.
Optimal longevity range: approximately 100–180 ng/mL in adults over 40. Very high (above 250 ng/mL) or very low (below 75 ng/mL) levels both warrant investigation.
DHEA-S (Dehydroepiandrosterone Sulphate)
What it measures: The sulphated storage form of DHEA — an adrenal hormone that serves as a precursor to both testosterone and oestrogen.
Why it matters for longevity: DHEA-S declines more steeply and consistently with age than almost any other measurable hormone — typically falling by 80–90% between age 25 and 75. It is used as a functional marker of adrenal reserve and biological ageing. Low DHEA-S is associated with reduced muscle mass, increased visceral fat, impaired immune function, and higher all-cause mortality in older adults.
Sex Hormones: Testosterone (Men) / Oestradiol (Women)
For men: Total and free testosterone decline approximately 1–2% per year from around age 30. Low testosterone is associated with reduced muscle mass, increased visceral adiposity, insulin resistance, cardiovascular risk, and cognitive decline. Free testosterone (the biologically active fraction) is more clinically informative than total testosterone alone.
For women: Oestradiol is the primary oestrogen with protective effects on cardiovascular health, bone density, cognitive function, and skin integrity. The perimenopause transition — marked by declining and fluctuating oestradiol — is increasingly recognised as a critical window for proactive health intervention, not just symptom management.
Omega-3 Index
What it measures: The percentage of EPA and DHA (omega-3 fatty acids) in red blood cell membranes — a reliable reflection of long-term omega-3 intake.
Why it matters for longevity: An Omega-3 Index below 4% is classified as high cardiovascular risk. Above 8% is considered optimal. The VITAL trial (over 25,000 participants) demonstrated significant reductions in cardiovascular events with omega-3 supplementation, particularly in people with low baseline fish intake.
Advanced Cardiovascular: Lp(a) and NMR Lipid Panel
Lp(a): Lipoprotein(a) is a genetically determined cardiovascular risk factor that does not respond to statins and is unaffected by lifestyle. It is tested once (levels are largely fixed) and provides important context for lifetime cardiovascular risk stratification. Available privately for ~£40–60.
NMR Lipid Panel: Nuclear magnetic resonance spectroscopy provides LDL particle number and size distribution — more granular than standard lipid panels. Small, dense LDL particles are more atherogenic than large buoyant particles even at equivalent LDL-C concentrations.
What to Say to Your GP
The most practical approach for the NHS-available tests is to combine your request under a "proactive cardiovascular and metabolic health review." Most GPs will authorise the majority of core markers under this framing without requiring clinical justification for each individual test.
A reasonable script:
"I'd like to do a proactive health review. I'm particularly interested in metabolic markers including fasting glucose and insulin, hs-CRP, homocysteine, vitamin D, and a full lipid panel including ApoB if your lab offers it. I'm not presenting with symptoms — I'm tracking long-term health."
If your GP declines specific markers, private blood testing in the UK has become highly accessible. Services including Medichecks and Randox Health offer comprehensive longevity panels for £150–350 that cover most of the extended panel above with home finger-prick or clinic venepuncture options.
Tracking Results Over Time: The Principle That Matters Most
A single blood test is a snapshot. A longevity protocol requires longitudinal tracking — ideally annual testing of the core panel with the same laboratory to ensure reference consistency.
The markers most informative as trends rather than absolutes include:
- eGFR — a declining trend within normal range is meaningful
- HbA1c — creeping upward within normal limits predicts future metabolic dysfunction
- hs-CRP — persistently elevated even at low levels signals chronic inflammation
- Testosterone / DHEA-S — trajectory of decline matters as much as absolute level
- Ferritin — gradual accumulation over years is the relevant pattern in iron overload risk
One of the things I've found genuinely useful from tracking my own biomarkers is the shift in perspective it creates — from reactive to proactive. You stop thinking about health in terms of whether you feel ill, and start thinking about where your trajectory is heading. It changes which interventions feel urgent. — Mat Stuckey, Founder, Longevity Formulas
For guidance on monitoring biological age with non-blood methods alongside these tests, our biological age calculator and guide to measuring biological age at home provide additional tracking frameworks.
How These Markers Connect to the Supplements You Take
Understanding your blood panel makes supplementation more targeted and more rational. Some direct connections:
- Elevated homocysteine → strong case for TMG, B12, folate; directly relevant to NMN + TMG stacking
- Low vitamin D → supplement D3+K2; see our Vitamin D3+K2 supplement
- Elevated hs-CRP / inflammageing markers → omega-3, magnesium, resveratrol; covered in our magnesium and longevity article
- High ferritin / oxidative stress markers → NAC for glutathione support; see our NAC supplement
- Declining metabolic markers (HbA1c, insulin) → NMN for NAD+ restoration and sirtuin activation; how NMN works in the body
- Elevated ApoB / cardiovascular risk → krill oil omega-3; see our Superba Krill Oil
For broader context on which longevity supplements have the strongest evidence base and where they sit in a protocol, our 10 best supplements for longevity article ranks by research quality.
Quick Reference: The Full Longevity Blood Panel
| Test | NHS Available? | Optimal Range | Primary Longevity Relevance |
|---|---|---|---|
| HbA1c | ✅ Yes | Below 39 mmol/mol | Glycation, metabolic ageing |
| Fasting glucose | ✅ Yes | 3.9–5.0 mmol/L | Insulin resistance screening |
| Fasting insulin | ⚠️ Request specifically | Below 7 mIU/L | Early insulin resistance |
| HOMA-IR | ⚠️ Calculated | Below 1.0 | Insulin sensitivity |
| Full lipid panel | ✅ Yes | See table above | Cardiovascular risk |
| ApoB | ⚠️ Request specifically | Below 0.7 g/L | Atherogenic particle count |
| hs-CRP | ⚠️ Request specifically | Below 0.5 mg/L | Inflammageing |
| Homocysteine | ⚠️ Request specifically | Below 7 µmol/L | Methylation, CVD, cognition |
| Vitamin D (25-OH) | ⚠️ Often restricted | 75–150 nmol/L | Immune, CV, all-cause mortality |
| Ferritin | ✅ Yes (with FBC) | 30–100 µg/L | Oxidative stress, iron overload |
| eGFR / creatinine | ✅ Yes | Above 90 | Kidney biological age |
| LFTs + GGT | ✅ Yes | GGT below 30 U/L | Liver health, oxidative burden |
| TSH | ✅ Yes | 0.5–2.0 mIU/L | Metabolic rate, cardiovascular |
| IGF-1 | ❌ Private | 100–180 ng/mL (40+) | mTOR / longevity signalling |
| DHEA-S | ❌ Private | Age-adjusted | Biological ageing marker |
| Testosterone (men) | ⚠️ Request | Age-adjusted | Healthspan, body composition |
| Oestradiol (women) | ⚠️ Request | Cycle/age adjusted | Cardiovascular, bone, cognition |
| Omega-3 Index | ❌ Private | Above 8% | Cardiovascular, inflammatory |
| Lp(a) | ❌ Private | Below 75 nmol/L | Genetic CVD risk (test once) |
Frequently Asked Questions
Which blood tests should I ask my GP for longevity? The highest-priority NHS-accessible tests are: HbA1c, fasting glucose and insulin, full lipid panel with ApoB, hs-CRP, homocysteine, vitamin D, ferritin, eGFR, LFTs, and TSH. For a complete longevity picture, add IGF-1, DHEA-S, sex hormones, and an Omega-3 Index through private testing.
Will my GP agree to these blood tests? Most core metabolic and cardiovascular markers can be requested under a proactive health review framing. Tests like fasting insulin, hs-CRP, and homocysteine may require a specific clinical justification or follow-up request. Tests such as IGF-1 and DHEA-S are generally only available privately.
What is the difference between a normal range and an optimal range? NHS normal ranges define the statistical boundary between disease and non-disease in the general population. Optimal ranges — as used in longevity medicine — define the narrower zone where the risk of long-term age-related disease is meaningfully lower. For example, an HbA1c of 46 mmol/mol is "normal" on the NHS; longevity-focused clinicians aim for below 39 mmol/mol.
How often should I get a longevity blood panel? Annually is the standard recommendation for core metabolic and inflammatory markers. Trend tracking over 3–5 years is where the real value lies. Lp(a) and genetic cardiovascular markers are typically tested once.
What private blood test services are available in the UK? Medichecks, Thriva, Randox Health, and Bluecrest Wellness all offer comprehensive longevity panels ranging from approximately £150–350. Most offer home finger-prick collection or clinic appointments.
Can blood tests tell you your biological age? Not directly, but several markers — eGFR, HbA1c, hs-CRP, DHEA-S, and telomere length — are used as proxies for biological ageing rate. Epigenetic clock testing (such as TruDiagnostic or Elysium Health's Index test) offers a more direct biological age estimate but requires specialist testing.
What does homocysteine tell you? Homocysteine reflects methylation efficiency and B-vitamin status. Elevated levels damage arterial walls, promote oxidative stress, and are associated with cognitive decline and cardiovascular disease. It is one of the most actionable markers on this list — high homocysteine typically responds well to B12, folate, B6, and TMG supplementation.
This article is for informational purposes only and does not constitute medical advice. Blood test interpretation should be discussed with a qualified healthcare professional. Reference ranges cited are general guides; individual clinical context always applies.
