I've got a blood test/physical coming up in a few months so I've been researching. I want to take Niacin for cholesterol but just found out, at doses high enough for positive effect on cholesterol, niacin is associated with impaired liver function. This applies to immediate release (IR) and slow/Long acting (extended release ER). The only one acceptable is the prescription one, go figure, Niaspan, it has a different formulation.
Here's the article:
//www.mdedge.com/jfponline/article/60319/hepatology/should-liver-enzymes-be-checked-patient-taking-niacin