Vitamin B3
Niacin helps turn food into usable energy.
The formula matches the form shown in the 3D model. Other forms of this vitamin can have different formulas.Loading molecular structure…
Nicotinic acid · Drag to rotate
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One representative form. Hydrogens omitted; bonds simplified.
PubChem · CID 938Where you can find it
- Poultry
- Fish
- Peanuts
- Whole grains
- Fortified cereals
What it does in the body
Niacin supports energy metabolism and normal cell function.
Recommended amounts & upper limit
US reference values for healthy adults aged 19–50, excluding pregnancy and breastfeeding. These are daily dietary intakes, not blood-test ranges or prescribed supplement doses. Other ages and life stages have different needs; see the original source.
- Men · RDA
- 16 mg NE/day
- Women · RDA
- 14 mg NE/day
- Upper limit · UL
- 35 mg/dayAdded niacin from supplements and fortified foods, not naturally occurring food niacin.
NE means niacin equivalents, accounting for niacin made from tryptophan.
How to read these levels
RDA means Recommended Dietary Allowance; AI means Adequate Intake, used when an RDA cannot be set. The upper limit (UL) is not a target or an exact toxicity threshold. Going below the RDA on one day does not diagnose deficiency. No established UL does not mean unlimited amounts are safe.
mg = milligrams; mcg = micrograms. 1 mg = 1,000 mcg. IU is vitamin-specific and cannot be converted with one rule for all vitamins.
What happens when the balance changes?
These are possible effects, not a diagnosis or a prediction from one low or high result.
Too little
Severe deficiency causes pellagra: sun-sensitive skin changes, digestive problems and mental changes; untreated disease can be fatal.
Body areas affected
Skin, digestive tract and brain.
Too much
Nicotinic acid can cause flushing. Large supplement doses can cause low blood pressure, raised blood sugar and liver damage.
Body areas affected
Skin, circulation and liver.
What about blood-test levels?
Blood-test levels and daily intake use different units and cannot be compared directly. Test methods, reference ranges and clinical context vary. Symptoms alone cannot establish a vitamin deficiency or toxicity; a clinician can decide which tests and treatment are appropriate.
The body connection
Both severe deficiency and high-dose supplements can affect several organs.
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