Are niacin pills giving my face a red flush?

Yes: Its a common side effect. Its a prostaglandin based reaction and thus nonsteroidals and asprin can be used to treat and prevent flushing. Usually the symptoms improve as the body acclimates to the drug.

Niacin.: Supplementing with 2000-3000mg of flush free Niacin daily can help to control your cholesterol levels quite nicely, even increasing your HDL and converting your LDL to a less harmful subtype. As a negative, Niacin can cause facial flushing and redness so get the flush free variety. And have your liver enzyme values monitored, as they can be affected by Niacin use.