NAD+ is a cellular helper for energy production and DNA repair that declines with age. Supplements the body converts into NAD+ reliably raise blood levels, but whether that produces real health benefits in people remains unsettled. Human signals are modest and mixed; the dramatic lifespan results come from animals, not humans. Short-term use is well tolerated; long-term safety is untested. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Whole-blood NAD+ | Track relative rise from baseline | Confirms the precursor is raising the NAD+ pool |
| Fasting glucose | 75–90 mg/dL | Screens metabolic status and any glucose effect |
| HbA1c | < 5.4% | Tracks longer-term glucose control |
| Fasting insulin | 2–6 µIU/mL | Assesses insulin sensitivity, the most-cited outcome |
| Lipid panel (LDL-C, HDL-C, triglycerides) | Triglycerides < 80 mg/dL; HDL-C > 50 mg/dL | Detects any lipid effect, relevant to niacin forms |
| ALT / AST (liver enzymes) | ALT < 25 U/L | Safety monitoring, chiefly for high-dose niacin |
| Homocysteine | 5–7 µmol/L | Flags methylation burden from high nicotinamide intake |
| hsCRP | < 1.0 mg/L | Tracks inflammation, a proposed NAD+ target |
Cadence: Baseline before starting, then repeat key markers at ~3 months, then every 6–12 months