What are the risks of taking nicotinamide?

In rare instances, nicotinamide may result in allergic reactions after an oral or intravenous dose. Most side effects of nicotinamide are mild, including a warm sensation that can be reduced with over-the-counter non-steroidal anti-inflammatory medications like aspirin, ibuprofen (Advil, Motrin) or naproxen (Naprosyn). An antihistamine taken 15 minutes before nicotinamide also is effective at reducing the warm sensation. Other mild side effects may include nausea, vomiting, upset stomach and diarrhea. More serious side effects may include liver toxicity, stomach ulcers and altered blood uric acid levels. Nicotinamide may alter blood sugar levels. Other possible side effects include: muscle damage, increased levels of blood creatine kinase and lactic acidosis. Side effects may also include: unusual heart rhythms, circulatory collapse, heart palpitations, blood clotting problems, tooth and gum pain, headache, dry eye, difficulty breathing, panic attack, anxiety, rash, blurred vision and decreased thyroid function. Fainting, lightheadedness and dizziness may occur, especially after alcohol use. Avoid taking large doses of vitamins unless recommended by your doctor. It is not recommended to take nicotinamide during pregnancy or breastfeeding.