Blood

Why blood matters for longevity

Blood is a liquid organ. It carries oxygen, nutrients, hormones, and immune cells to every tissue in the body, and it hauls metabolic waste back out. The composition of your blood at any given moment reflects how well your metabolism, immune system, liver, kidneys, and endocrine glands are performing. That makes it the single most information-dense sample you can provide for health assessment.

What separates proactive health management from conventional medicine is the question you're asking. A standard checkup asks: "Are you sick?" A longevity-oriented blood analysis asks: "How well are you aging, and where are the early warning signs?" Those are very different questions, and they require different tests, different reference ranges, and a different approach to interpretation ^[1].

Blood testing beyond the basics

A complete blood count (CBC) and basic metabolic panel are a reasonable starting point, but they miss a lot. For a fuller picture, you need advanced lipid markers like ApoB and Lp(a), fasting insulin alongside fasting glucose, inflammatory markers like hs-CRP and homocysteine, a complete thyroid panel, and sex hormones. A 35-year Swedish cohort study found that centenarians had consistently more favorable blood biomarker values than non-centenarians, with differences visible as early as age 65 ^[2].

Standard "normal" ranges on lab reports are derived from the general population, which includes plenty of metabolically unhealthy people. A fasting glucose of 99 mg/dL is technically normal but far from optimal. Longevity physicians work with tighter reference ranges that correlate with the lowest disease and mortality risk ^[3].

Key blood markers and what they reveal

Metabolic health

Fasting insulin is arguably the most underappreciated metabolic marker. It rises years before fasting glucose does, making it the earliest signal of insulin resistance. HbA1c gives you a 2-3 month average of blood sugar. HOMA-IR, calculated from glucose and insulin together, provides a single insulin-resistance score. These three markers together catch metabolic dysfunction much earlier than glucose alone ^[4].

Cardiovascular risk

Forget total cholesterol as a meaningful risk predictor. ApoB measures the actual number of atherogenic particles in your bloodstream, and it's the strongest single predictor of atherosclerotic cardiovascular disease. Lp(a) is largely genetic, can't be lowered much with lifestyle, and every adult should know their level. A 2023 meta-analysis of over 267,000 UK Biobank participants identified a sex-specific combination of blood biomarkers that predicted all-cause mortality with strong accuracy ^[5].

Inflammation and immune function

Chronic low-grade inflammation drives virtually every age-related disease. Hs-CRP below 0.5 mg/L is the target for longevity-focused individuals, not just the "low risk" cutoff of 1.0 mg/L used in cardiology. Homocysteine, tied to B-vitamin status, is both an inflammatory marker and an independent cardiovascular risk factor. The neutrophil-to-lymphocyte ratio from a simple CBC adds a surprisingly powerful immune-balance snapshot ^[6].

How to get the most from your blood work

Consistency matters more than perfection. Fast for 12-14 hours, draw blood between 7-9 AM, skip intense exercise the day before, and retest under the same conditions every 3-6 months. Trends over time tell you far more than any single reading. Don't rely on the lab's "normal/abnormal" flags alone. Request full numerical values and track them in a spreadsheet or health platform. If your physician won't order comprehensive panels, direct-to-consumer lab services can fill the gap ^[7].