High doses of nicotinic acid should be avoided in those with impaired liver function, gall bladder disease, gout, asthma, cardiac arrhythmias, inflammatory bowel disease, migraine, or an active peptic ulcer. Nicotinic acid in high doses can reduce blood pressure and should be avoided by those taking drugs to control high blood pressure. Niacin in high doses can affect glucose metabolism and should be used cautiously by diabetics.