Niacin: Dosages of Niacin in excess of 100 mg daily
may cause flushing of face, arms, and chest, itching
and nausea known as Niacin Flush. When taken as
directed, multivitamins are not expected to cause
serious side effects. Less serious side effects may
include: upset stomach, headache, or unusual or
unpleasant taste in the mouth.