Niacin UL Question


Hey everyone!

I’m noticing something interesting while creating my Toxicity Alert System in my spreadsheet. I started noticing this when I plugged in my values for Niacin, of which I obtain 100% of from one multivitamin, and they were at 250% the recommended value, which is 20mg.

This source and this source both indicate that the UL for Niacin is 35mg / day. However, the Wikipedia article, as well as this source indicate that adverse effects only start to occur at +1.5g / day.

If adverse effects only start to occur at 1.5g or more, then why is the UL only 35mg? Is there an error somewhere in one or more of the sources? I find it odd that my multivitamin would by default contain what these sources are confirming is a level of Niacin well above the UL.

Anyone else with additional information or knowledge in this regard who could provide their input would be very appreciated.

Thanks! :slight_smile:


Niacin is sold over the counter at pharmacies here in Canada in tablet form containing 500 mg with a recommended dosage of one tablet daily. I have taken it at that rate for several weeks at a time with no untoward effects other than the well-known “niacin flush” caused by prostaglandin stimulation. As usual, I guess there is a wide variation of opinion about appropriate dosage of this vitamin (as also with vitamins C, D, E, A etc.


Here’s a link to the DRI tables put out by the National Institutes of Health: The upper limit for males 19 and over is 35mg, but the RDA is only 16mg.