Niacin is a B vitamin the body makes. The body uses niacin to turn food into energy. It helps keep the nervous system, digestive system, and skin healthy.

People may take niacin, also called vitamin B-3, as part of a daily multivitamin. But most people get enough niacin from the food they eat. Foods rich in niacin include yeast, milk, meat, and cereals.

Some people use prescription niacin (Niacor) to help manage cholesterol.

The suggested daily amount of niacin for adults assigned male at birth is 16 milligrams (mg) a day. For adults assigned female at birth who aren't pregnant, the dose is 14 mg a day.

Research on the use of niacin you take by mouth to treat certain conditions shows:

• High cholesterol. Prescription niacin raises high-density lipoprotein (HDL) cholesterol. This is the "good" cholesterol that helps remove low-density lipoprotein (LDL), the "bad" cholesterol, from the blood. Even though niacin may raise HDL cholesterol, research suggests that niacin therapy isn't linked to lower rates of death, heart attack, or stroke.
• Niacin deficiency, also called pellagra. Niacin and a nutrient called niacinamide treat or prevent a lack of niacin. This condition isn't common in the United States.

Experts believe niacin to be safe when taken by mouth in typical amounts.

High doses of prescription niacin can cause:

• Skin flushing and dizziness.
• Itching.
• Upset stomach and vomiting.
• Belly pain.
• Loose stools.
• Gout.
• Liver damage.
• Diabetes.

Serious side effects are likely for people who take between 2,000 and 6,000 mg of niacin a day. If you think you might have taken too much niacin, seek medical help right away.

If you have a liver condition, a peptic ulcer, or very low blood pressure, called hypotension, don't take large amounts of niacin. The supplement has been linked with liver damage. Liver damage can cause hypotension and might make a peptic ulcer active.

Taking niacin also might make allergies, gallbladder conditions, and symptoms of some thyroid conditions worse. If you have diabetes, niacin can affect how you manage your blood sugar. Use niacin with care if you have gout. Niacin can cause too much uric acid in the blood, called hyperuricemia. This raises the risk of gout.

If you're pregnant, don't take prescription niacin for high cholesterol. But if you need niacin to prevent or treat lack of niacin, called deficiency, niacin is likely safe to take during pregnancy and breastfeeding. Use it only as your healthcare professional tells you.

Possible interactions include:

• Alcohol. Taking niacin with alcohol might raise the risk of liver damage. And it might make niacin side effects, such as flushing and itching, worse.
• Allopurinol (Lopurin, Zyloprim). If you take niacin and you have gout, you might need to take more of this gout medicine to manage your gout.
• Anticoagulant and antiplatelet medicines, herbs and supplements. These types of medicines, herbs and supplements limit blood clotting. Taking niacin with them might raise the risk of bleeding.
• Blood pressure medicines, herbs and supplements. Niacin might add to the effect of medicines, herbs and supplements that manage blood pressure. This could raise the risk of low blood pressure, also called hypotension.
• Chromium. Taking niacin with chromium might lower blood sugar. If you have diabetes and take niacin and chromium, watch your blood sugar levels.
• Diabetes medicines. If you have diabetes, niacin can affect blood sugar management. You might need to change the dose of the diabetes medicines.
• Medicines, herbs and supplements that cause liver damage , called hepatotoxic.  Niacin can cause liver damage. So don't take it with medicines, herbs or supplements that also can cause liver damage.
• Statins. Research shows that taking niacin with these cholesterol medicines does little more than statins alone. Taking niacin with statins might raise the risk of side effects.
• Zinc. Taking zinc with niacin might worsen niacin side effects, such as flushing and itching.