I’m also very safety-conscious; I’m looking for a health benefit, not a health risk.
That being said, you need to keep in mind what a “larger dose” or "too much " is.
The RDI for adult males for Niacin is 16 (14 for females.)
The UL for Niacin intake/supplements is 35 mg based on the risk of the flushing reaction, which is minor and not a health risk, and tends not to persist (at these dosages.)
I take a multivitamin that supplies 190 mg per day, but I take it split into at least two doses. I’ve never had a flush reaction with this product; some people have an initial flush, but reports are that it goes away.
In studies, they have found more serious side effects, such as signs of hepotoxicity (liver damage), “observed at intakes as low as 750 mg of niacin per day for less than three months (84, 85)” (from the LPI Niacin page).
Niacin is used for treatment of dyslipidemia (abnormal fat or cholesterol in the blood) at levels of 1000 mg and 1500 mg per day; at these levels, some people have persistent flushing. Also,you must monitor for liver problems - they are rare, but it’s possible. Here’s a short-term safety study of 148 patients, 1/3 of them dosing at 1000 mg and 1/3 of them dosing at 1500 mg per day. Result: “Four patients discontinued participation because of inadequate glucose control. Rates of adverse event rates other than flushing were similar for the niacin and placebo groups. Four patients discontinued participation owing to flushing (including 1 receiving placebo). No hepatotoxic effects or myopathy were observed.”
So the safety profile of niacin is well established, and the 35 mg upper limit is conservative; most of the few people who flush at that level will not continue to flush. That being said, you can always find someone very sensitive to flushing - note that in the last study I cited, one of the four people who quit the study because of flushing was actually receiving placebo, and not getting any niacin at all!