I spent years assuming that if my doctor ran a blood test and didn’t call me, everything was fine. It took me a while to realise that “normal” and “optimal” are two very different things — and that the standard panel most GPs order leaves out some of the most informative markers.
This is the panel I now track, why each test matters, and what the target ranges look like through a longevity lens rather than a “just not sick” lens.
Why the Standard Panel Isn’t Enough
A typical GP-ordered blood test will catch acute problems — anaemia, thyroid collapse, wildly out-of-range glucose. What it won’t catch is the slow drift toward metabolic dysfunction that happens years before anything shows up as “abnormal.”
The markers that matter most for longevity aren’t exotic. They’re just not on the default order form.
Metabolic Health
Fasting insulin is the test I wish I’d known about years ago. It rises long before glucose or HbA1c do — we’re talking a 10-15 year head start on detecting insulin resistance. Yet most doctors skip it entirely. The optimal range is below 5 uIU/mL. Combine it with fasting glucose and you can calculate HOMA-IR, a simple score of insulin resistance. Target: below 1.0.
HbA1c reflects your average blood sugar over the past two to three months. The lab flags anything below 5.7% as normal, but for longevity purposes, 4.8–5.2% is where you want to be. An HbA1c of 5.6% is technically fine by clinical standards, yet research links it to measurably higher cardiovascular risk. Worth knowing.
Fasting glucose is the most commonly ordered metabolic marker and also the latest to move. It won’t tell you much until things have already gone wrong. That said, consistently above 90 mg/dL warrants a closer look even when it reads as “normal.” Optimal range: 72–88 mg/dL.
Uric acid doesn’t get talked about enough. It’s an early marker of metabolic dysfunction — independently associated with hypertension, insulin resistance, fatty liver, and cardiovascular mortality. If you eat a lot of fructose or red meat, or you’re not well-hydrated, it can creep up quietly. Optimal: 3.5–5.0 mg/dL.
Cardiovascular Risk
ApoB is the most important cardiovascular test that most doctors still don’t order. Standard LDL-C measures the cholesterol content inside LDL particles. ApoB counts the particles themselves — and particles are what damages arterial walls. Two people can have identical LDL-C with very different ApoB levels and very different actual risk. The European Society of Cardiology now endorses ApoB as a primary risk marker. Optimal: below 70 mg/dL. Ask for it specifically.
Lp(a) only needs to be tested once in your life — it’s almost entirely genetically determined and doesn’t change much regardless of lifestyle. About one in five people carry elevated levels, which can double or triple heart attack risk independent of everything else. There’s no approved treatment yet, which is why many doctors argue it’s not worth testing. I disagree. Knowing you have high Lp(a) changes how aggressively you should manage every other risk factor. Test it once, know your number.
Standard lipid panel is still worth having, particularly for triglycerides (a clean metabolic health signal) and the TG/HDL ratio (a reliable proxy for insulin resistance). Below 70 mg/dL for triglycerides and a TG/HDL ratio below 1.0 is where you want to be.
Inflammation
hs-CRP (high-sensitivity C-reactive protein) measures low-grade chronic inflammation. Labs mark anything below 3.0 mg/L as normal. But studies on long-lived populations show consistently low hs-CRP — ideally below 0.5 mg/L. If yours comes back elevated, retest before drawing conclusions. It spikes from infection or hard training.
Homocysteine is an amino acid that reflects how well your body is methylating — essentially a B-vitamin status check. Elevated levels are associated with cardiovascular disease and dementia risk. Optimal: below 8 umol/L. If it’s high, the first thing to check is B12 and folate.
Hormones
Thyroid: TSH, Free T4, and Free T3. Most doctors order TSH alone and call it done. That tells you almost nothing about what’s actually happening at the cellular level. Free T3 is the active hormone. Optimal TSH: 1.0–2.5. Important: if you take biotin supplements, stop them five days before your blood draw — biotin interferes with thyroid assays.
Testosterone: total, free, and SHBG. Total testosterone alone is only half the picture. SHBG determines how much is actually available. Two men with identical total T can have very different free T depending on SHBG. Low SHBG is also an independent signal of insulin resistance. Draw must be before 10 AM.
Nutrient Status
This is where blood testing connects directly to your supplement stack. Without these markers, you’re flying blind.
Vitamin D (25-OH) — direct measure of your D3 supplementation. Optimal: 40–60 ng/mL. Test in late winter to catch your lowest point.
RBC magnesium (or serum as a minimum) — serum magnesium stays normal until you’re genuinely depleted. RBC magnesium is a better measure of tissue status. Optimal: 5.2–6.5 mg/dL. Harder to get through standard labs.
Zinc and copper — must be tested together if you supplement zinc. Zinc-induced copper deficiency develops slowly without obvious symptoms until it’s serious.
Omega-3 index — EPA and DHA as a percentage of red blood cell membranes. The only reliable way to know if your omega-3 supplementation is working. Optimal: 8–12%. Requires a private lab or home test kit.
Ferritin and iron panel — both ends of the spectrum cause problems. Haemochromatosis is the most common genetic disorder in Europeans (~1 in 200). Optimal ferritin: 40–100 ng/mL.
B12 and folate — optimal B12 is above 500 pg/mL. Most labs flag deficiency too conservatively at 200.
Organ Function
Liver enzymes: ALT, AST, and GGT. GGT in particular is a marker of oxidative stress. Lab normal goes up to 56–60 U/L; longevity-optimal is below 25 for all three. Avoid intense training 48 hours before your draw.
Kidney: creatinine and cystatin C. If you take creatine, creatinine is not a reliable kidney marker for you — creatine supplementation raises it and can make your eGFR look falsely low. Cystatin C is unaffected by creatine and gives the real picture. Note your creatine use on the lab form.
CBC with differential. Standard but important. The neutrophil-to-lymphocyte ratio (NLR) is emerging as a useful inflammation marker — optimal is below 2.0.
Summary: What to Test and Target Ranges
| Marker | Optimal Range | Frequency |
|---|---|---|
| Fasting insulin | <5 uIU/mL | Annually |
| HOMA-IR | <1.0 | Annually |
| HbA1c | 4.8–5.2% | Annually |
| Fasting glucose | 72–88 mg/dL | Annually |
| Uric acid | 3.5–5.0 mg/dL | Annually |
| ApoB | <70 mg/dL | Annually |
| Lp(a) | <30 mg/dL | Once |
| Triglycerides | <70 mg/dL | Annually |
| TG/HDL ratio | <1.0 | Annually |
| hs-CRP | <0.5 mg/L | Annually |
| Homocysteine | <8 umol/L | Annually |
| TSH / Free T4 / Free T3 | TSH 1.0–2.5 | Annually |
| Total T / Free T / SHBG | Context-dependent | Annually |
| Vitamin D (25-OH) | 40–60 ng/mL | Annually |
| RBC Magnesium | 5.2–6.5 mg/dL | Annually |
| Zinc + Copper | Monitor ratio | Annually |
| Omega-3 Index | 8–12% | Annually |
| Ferritin | 40–100 ng/mL | Annually |
| B12 / Folate | B12 >500 pg/mL | Annually |
| ALT / AST / GGT | <25 U/L each | Annually |
| Creatinine + Cystatin C | Per lab range | Annually |
| CBC with differential | NLR <2.0 | Annually |
You don’t need all of this every draw — Lp(a) is one-time, and once vitamin D and omega-3 levels are dialled in, you might recheck every other year. But the metabolic markers, ApoB, and organ function are worth tracking annually. Trends matter as much as individual numbers.
The goal isn’t to become obsessed with data. It’s to stop finding out something was quietly wrong for a decade once it’s already a problem.
If you’re in Spain and want a practical guide to actually getting these tests — navigating CatSalut, Sanitas, and private labs — I wrote a companion piece: A Practical Guide to Blood Testing in Spain.
This article is for informational purposes only and does not constitute medical advice. Consult your doctor before making changes to your health monitoring or treatment plan.
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