I know of three possible reasons:

- your supplement is a dud

- you took niacin too often (best to do it once a few days as body adapts quickly)

- you have a gene mutation that prevents you from absorbing enough B3 (common in some schizophrenia cases that can be managed by huge doses of daily B3, like 4-10g)

> you took niacin too often

Oh yeah, I was taking it daily when I stopped flushing. Makes sense.