Niacin, an essential B vitamin that at doses far above dietary needs is a long-established drug for changing blood fats, reliably lowers harmful cholesterol and an inherited cholesterol-carrying particle while raising so-called good cholesterol. Large modern trials adding it to cholesterol-lowering statin drugs found no reduction in heart events and more side effects. Evidence is strongest where other cholesterol treatments are unsuitable, weakest as a general longevity supplement. (Full Review)
| Marker | Target | Why |
|---|---|---|
| ALT and AST (liver enzymes) | ALT roughly 7–55 U/L; AST 8–48 U/L | Safety check: use stops if persistently ≥3× upper limit |
| Fasting glucose | 70–99 mg/dL | Safety check: rising values may change use |
| HbA1c | 4.0–5.6% | Safety check for new-onset diabetes |
| Uric acid | About 3.4–7.0 mg/dL (men); 2.4–6.0 mg/dL (women) | Safety check for gout risk |
| LDL, HDL, triglycerides | No established target; track change from own baseline | Expected to change with niacin |
| Apolipoprotein B | No established target; track change from own baseline | Expected to change with niacin |
| Lipoprotein(a) | No established target; track change from own baseline | Expected to change with niacin |
| Creatine kinase | About 30–200 U/L | Safety check with statins |
| Platelets and prothrombin time | Platelets 150–450 ×10⁹/L; prothrombin time about 11–13.5 seconds | Safety check with anticoagulants |
| Blood NAD+ | No established target; track change from own baseline | Expected to change with niacin |
Cadence: Baseline before gram doses; liver enzymes every 6–12 weeks in year one, then about every 6 months; glucose, HbA1c, uric acid and lipids at 3 months and after dose increases, then every 6–12 months; creatine kinase if muscle symptoms occur.