Safety and Tolerability of NAD Supplementation

Nicotinic Acid (Niacin) Adverse Effects

Flushing is the most characteristic side effect of oral nicotinic acid, typically appearing on the face, arms, and chest within 30 minutes of ingestion and resolving within 60 minutes. 1
High‑dose nicotinic acid (≈ 3 g/day) can cause hepatotoxicity ranging from mild liver‑enzyme elevation to acute liver failure requiring transplantation. 1
In elderly patients, transient hypotensive episodes have been reported at doses as low as 30 mg/day of nicotinic acid. 2, 3, 4
The established upper intake limit for free nicotinic acid is 10 mg/day, based on the prevalence of flushing at clinical dosing levels. 2, 3, 4

Nicotinamide does not induce flushing, distinguishing it from nicotinic acid. 3, 4
The tolerable upper intake level for nicotinamide is set at 12.5 mg per kilogram body weight per day (≈ 900 mg/day for an average adult). 2, 3, 4
Prolonged studies in diabetic populations have shown no adverse effects at doses up to 25 mg per kilogram body weight per day. 3, 4

The European Society for Clinical Nutrition and Metabolism (ESPEN) guideline states that nicotinamide intake of approximately 900 mg/day for adults presents no safety concerns within the range typically consumed in foods. 2, 3, 4