So basically.

You should probably refrain from taking more than you really "feel" like you can. Niacin affects everyone differently, depending on your body chemistry. You probably want to stick to the recommended dosage at first and if you feel comfortable (and paranoid) You could possibly think about doubling it the next day.

It's a vitamin, so you can't really "overdose" on it.. but you can make yourself feel pretty uncomfortable if you abuse it. So be smart.

Bob.