Niacin (B3)

niacin · niacinamide · nicotinic acid · nicotinamide · vitamin B3

Snapshot

Indications	Contraindications
Dyslipidemia (statin-intolerant)¹ Severe hypertriglyceridemia¹ Pellagra treatment¹ Skin cancer chemoprevention² Keratinocyte carcinoma in transplant recipients³ COVID-19 recovery support⁴	Active hepatic disease⁵ Severe gout¹ Active peptic ulcer disease¹

Niacin (vitamin B3) is a water-soluble essential B vitamin that the body converts to nicotinamide adenine dinucleotide (NAD) and its phosphorylated form (NADP), coenzymes required by more than 400 enzymes across cellular energy production, genome maintenance, and antioxidant defense.¹ Supplementation is used principally for dyslipidemia management and pellagra prevention; nicotinamide (the non-flushing form) is used for skin cancer chemoprevention, and both forms are studied as NAD precursors in aging-related conditions.¹ The patients most likely to reach for supplemental niacin are those with low high-density lipoprotein (HDL) cholesterol who cannot tolerate statins, individuals at high risk for keratinocyte carcinomas, and those with frank or marginal deficiency from undernutrition, alcohol use disorder, or malabsorptive disease.¹

The nicotinic acid evidence for lipid modification is strong in mechanistic terms: it raises HDL and lowers low-density lipoprotein (LDL), triglycerides, and lipoprotein(a), yet two large randomized controlled trials (RCTs) in patients on statins found no reduction in major vascular events and higher rates of diabetes, gastrointestinal harm, and stroke, conclusions endorsed by a 2017 Cochrane review and a 2018 systematic review.¹ The American College of Cardiology and American Heart Association therefore advise against niacin as an add-on to statin therapy and reserve it for severe hypertriglyceridemia or statin-intolerant patients.¹ For skin cancer chemoprevention, a large 2025 retrospective cohort study of oral nicotinamide found a significant reduction in skin cancer risk across more than 12,000 patients, with the greatest benefit after a first skin cancer.² In a 2025 RCT in symptomatic COVID-19 outpatients, nicotinamide improved physical performance recovery and reduced post-COVID symptoms compared with placebo.⁴ A 2024 metabolomics study found serum levels of the terminal niacin metabolites 2PY and 4PY were linked to higher three-year major adverse cardiovascular event risk in two validation cohorts. In mice, 4PY but not 2PY triggered vascular inflammation.⁶ More than 13,000 products listing niacin are available as powders, capsules, and tablets in immediate-release, extended-release, and flush-free (inositol hexanicotinate) forms; see Form comparison for bioavailability differences.

The most consequential safety signal is hepatotoxicity: LiverTox rates niacin as a well-established cause of clinically apparent liver injury at high doses, with sustained-release formulations carrying the greatest risk, and the National Institutes of Health Office of Dietary Supplements (ODS) notes that pharmacologic nicotinic acid at these doses also impairs glucose tolerance and should be monitored with hepatic transaminases, fasting glucose, and uric acid per the American College of Cardiology and American Heart Association joint statement.^{1, 5}

Last updated October 8, 2026. Read how we make monographs.

In the full monograph

65 sources, 46 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources