The 10 Biomarkers Worth Tracking Before You Turn 40

Standard blood panels were designed to catch disease. By the time they flag something, the underlying dysfunction has usually been building for years. A smarter approach is to track the markers that reveal drift, the gradual erosion of optimal function that precedes clinical disease by a decade or more.

The Metabolic Core

• ✓Fasting insulin, the earliest signal of metabolic dysfunction. Most labs don't include it without you asking. Optimal: below 5 μIU/mL.
• ✓HbA1c, your 3-month average blood sugar. Functional practitioners often aim for 4.8-5.2%, below the conventional "normal" cutoff of 5.7%.
• ✓Triglycerides-to-HDL ratio, a proxy for insulin resistance. Below 1.5 is excellent; above 3.0 signals significant metabolic stress.

Inflammation

• ✓hs-CRP, high-sensitivity C-reactive protein. The standard version misses low-grade chronic inflammation. Target: below 0.8 mg/L.
• ✓Homocysteine, damages arterial walls when elevated. Optimal: below 7 μmol/L. Responds well to methylated B vitamins.

Hormonal and Nutritional Markers

• ✓Free testosterone, declines with age and chronic stress. Low levels affect energy, cognition, and body composition before classic symptoms appear.
• ✓DHEA-S, a proxy for adrenal reserve and biological aging rate. Peaks in your 20s and steadily declines.
• ✓Vitamin D (25-OH), optimal range 50-80 ng/mL, not the conventional "sufficient" threshold of 30.
• ✓Omega-3 Index, ratio of EPA and DHA in red blood cells. Below 4% is high-risk; above 8% is protective.
• ✓VO2 max, technically a fitness test, but the single most powerful predictor of longevity currently measurable. Low VO2 max carries mortality risk comparable to smoking.