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Medically reviewed by Vanessa Niles, R.N., M.D., F.A.C.O.G. —
Definition
Niacin, in plain English
Niacin is the name for vitamin B3. On labels it usually means nicotinic acid, nicotinamide (also called niacinamide), or both. NIH says niacin helps turn the food you eat into the energy you need.
Adults need 16 mg a day (men) or 14 mg a day (women) of niacin equivalents, a unit that also counts the niacin your body makes from tryptophan. Poultry, beef, fish, nuts, legumes and grains are common sources, and many breads and cereals are fortified.
- Also called
- Vitamin B3
- Adult RDA
- 16 mg NE (men), 14 mg NE (women)
- Upper limit
- 35 mg/day from supplements
For your treatment
What niacin means for NAD+ therapy
Niacin supplements and NAD+ therapy aren't interchangeable. For adults, NIH sets the upper limit for niacin from supplements and fortified foods at 35 mg a day unless a doctor is supervising; high doses can cause flushing and, at prescription levels, liver problems.
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Questions
Niacin: common questions
What is niacin?
Niacin is vitamin B3, an essential nutrient the body turns into NAD and NADP. It includes nicotinic acid and nicotinamide and comes from foods such as poultry, fish, nuts and grains.
Is niacin the same as NAD+?
No. Niacin is the vitamin; NAD+ is the coenzyme your body makes from it.
Can you get too much niacin?
From food, it's very unlikely. From supplements, NIH sets the adult upper limit at 35 mg a day, based on flushing. Higher amounts should only be taken under a doctor's care.
Can I take precursors with NAD+ therapy?
Combining them hasn't been studied. Tell your provider about any NR, NMN, niacin or other supplements before you start.
Can I get enough NAD+ from food?
Food supplies niacin and tryptophan, which your body turns into NAD+, and NIH says most people in the U.S. get enough niacin. NAD+ in food is largely broken down during digestion.
Do precursors and NAD+ therapy do the same thing?
Both aim to raise NAD+, by different routes: precursors are converted by the body, while spray and injections deliver NAD+ itself. They haven't been compared in trials.
Keep learning
Related NAD+ terms
Terms that connect to niacin, each explained on its own page.
- Vitamins & precursorsNicotinic acidNicotinic acid is the form of vitamin B3 most people mean by 'niacin.' In large doses it causes skin flushing, and it has been used as a prescription cholesterol medicine.
- Vitamins & precursorsNicotinamideNicotinamide, also called niacinamide, is a form of vitamin B3. It's the building block the body recycles to remake NAD+, and unlike nicotinic acid it doesn't cause skin flushing.
- Treatment & safetyNiacin flushNiacin flush is warmth, redness, itching or tingling of the skin, usually on the face and chest, after a large dose of nicotinic acid. It's usually harmless but uncomfortable.
- Treatment & safetyPellagraPellagra is the disease caused by severe niacin (vitamin B3) deficiency. It's classically described by three Ds: dermatitis, diarrhea and dementia.
- Vitamins & precursorsNAD+ precursorAn NAD+ precursor is any molecule the body can turn into NAD+. The main ones are tryptophan, nicotinic acid, nicotinamide, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN).
Guides that cover niacin
- What Is NAD Injections? A Simple, Friendly Beginner's GuideNew to NAD+ injections? Learn what they are, how a shot under the skin works, what research shows, who should skip them and what they cost at NADMedics.NAD+ injections
- NAD+ Injection Dosage Per Day: How Much Is Truly Safe Daily?Is there a safe daily NAD+ injection dose? No limit has been established. See what studies show about daily NAD+, side effects and why your provider sets it.NAD+ injections
Official sources
Niacin: sources and official resources
Official government and research sources behind this page, so you can check the facts yourself.
- NIH Office of Dietary SupplementsNiacin: Health Professional Fact Sheet
Explains how the body turns niacin (vitamin B3) into NAD, a coenzyme used by more than 400 enzymes.
- NIH Office of Dietary SupplementsNiacin: Fact Sheet for Consumers
What niacin (vitamin B3) does, how much adults need and which foods provide it.
- MedlinePlus (National Library of Medicine)Niacin and niacinamide (Vitamin B3)
Uses, safety and interactions of the two main forms of vitamin B3.
- NIH National Library of Medicine (StatPearls)Niacin (StatPearls, archived)
Clinical review: NAD and NADP as the active forms of niacin, and niacin's use as a cholesterol drug.
Medically reviewed by Dr. Vanessa Niles, R.N., M.D., F.A.C.O.G., on October 12, 2026. This glossary is general education, not medical advice. NAD+ has no FDA-approved use, and compounded NAD+ is not FDA-approved or evaluated by the FDA for safety or effectiveness. Talk with a licensed provider before starting any supplement or treatment.
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