Is too much niacin bad for the liver?

If you're taking the normal amounts of niacin even under 500 milligrams I highly doubt you're ever going to have liver problems. Look at the benefits of niacin. Niacin for schizophrenia, blood pressure. Take a look at even the mitochondria that inside there, you have the Krebs cycle. B3 is an necessary nutrient for that cycle to work.