B3 Safety & Side Effects
Our assessment
Based on FDA data, dietary supplements containing 30 mg or more of nicotinic acid can cause predictable side effects. The most common reaction involves the skin on your face, arms, and chest turning red, burning, tingling, and itching, which can also be accompanied by headaches, rashes, and dizziness FDA FAERS ↗. These effects are dose-dependent and typically occur shortly after taking the supplement.
Safety profile
At higher prescription-level doses of 1,000 mg or more per day, the side effects become more severe. FDA data reports that these can include low blood pressure (increasing the risk of falls), extreme tiredness, and high blood sugar levels FDA FAERS ↗. While report counts for each specific severe side effect are not available in the provided data, the risk of these events increases with higher dosages FDA FAERS ↗.
How it works
Niacin is a B vitamin that helps convert food into energy. The flushing reaction is a known vasodilatory effect of nicotinic acid, which widens blood vessels and causes the characteristic redness and warmth NIH ODS ↗. Data on the precise mechanism of action for these side effects is limited to the provided FDA summary.
Our recommendation
Individuals taking tuberculosis drugs such as isoniazid and pyrazinamide should be cautious, as these medications can interfere with the body's ability to convert tryptophan to niacin NIH DSLD ↗. Anyone starting a niacin supplement, especially at doses above 30 mg, should be aware of the flushing reaction and monitor for symptoms of low blood pressure or changes in blood sugar FDA FAERS ↗. Consult a healthcare provider before taking high-dose niacin, particularly if you have diabetes or are at risk of falls.
AI-assisted analysis. Data sourced from NIH ODS and FDA.
Safety Overview
The niacin that food and beverages naturally contain is safe. However, dietary supplements with 30 mg or more of nicotinic acid can make the skin on your face, arms, and chest turn red and burn, tingle, and itch. This can also lead to headaches, rashes, and dizziness. If you take nicotinic acid as a medication in doses of 1,000 or more mg/day, it can cause more severe side effects . These include: Low blood pressure (which can increase the risk of falls) Extreme tiredness High blood sugar levels Nausea , heartburn, and abdominal pain Blurred or impaired vision and fluid buildup in the eyes Long-term treatment, especially with extended-release forms of nicotinic acid, can cause liver problems, including hepatitis and liver failure. Niacin in the form of nicotinamide has fewer side effects than nicotinic acid. However, at high doses of 500 mg/day or more, nicotinamide can cause diarrhea and easy bruising and can increase bleeding from wounds. Even higher doses of 3,000 mg/day or more can cause nausea, vomiting, and liver damage. The daily upper limits for niacin from dietary supplements are listed below.
Drug Interactions
Niacin dietary supplements can interact or interfere with certain medicines that you take, and some medicines can lower niacin levels in your body. Here are some examples: Tuberculosis drugs (such as isoniazid and pyrazinamide) interfere with the body’s ability to convert tryptophan to niacin. This interference can lower niacin levels in your body. High doses of nicotinic acid (1,500 mg/day or more) can raise blood sugar levels and interfere with the effectiveness of diabetes medications. These doses can even raise blood sugar levels in people who don’t have diabetes. Tell your doctor, pharmacist , and other health care providers about any dietary supplements and prescription or over-the-counter medicines you take. They can tell you if the dietary supplements might interact with your medicines. They can also tell you if the medicines might interfere with how your body absorbs , uses, or breaks down niacin and other nutrients.