Flushing or hot flashes, particularly in the face, neck and ears, are the most common side effects. This warm sensation may occur when individuals first begin taking nicotinic acid or when the dose is increased.  To counteract this unpleasant effect, physicians may prescribe aspirin, a non-steroidal anti-inflammatory (NSAID) or an antihistamine to be taken before the niacin to reduce the risk of flushing.

Another common side effect is dizziness or lightheadedness, especially when rising from a seated position or after lying down. Getting up slowly may help reduce this side effect. This side effect usually lessens after a few weeks, as the body become more accustomed to the medication. Patients should notify their physician immediately if they experience any side effects such as:

Other potential side effects include:

• Headache
• Palpitations and/or an abnormal heartbeat (arrhythmia)
• Gas and/or indigestion
• Diarrhea
• Nausea and/or vomiting
• Dry and/or itchy skin
• Fever
• Frequent urination
• Pain in joints, side, lower back and/or stomach
• Muscle aching or cramping
• Swelling (edema) of the feet or lower legs
• Excessive thirst
• Tiredness, weakness and/or fatigue

Whenever vitamin B3 is taken in high doses (especially the time-release versions), there are concerns regarding a number of conditions that could develop, including:

• Liver inflammation
• Gout
• Peptic ulcers
• Elevated blood sugar (glucose) levels and insulin resistance