Niacin (Vitamin B3)
The flush is the tell. It means you took nicotinic acid, and it says nothing about whether the dose was doing anything.
Niacin is vitamin B3, and the name covers two compounds that part company above dietary doses. Nicotinic acid triggers the flush: a prostaglandin-mediated wave of heat and redness across the face and chest, starting within about 20 minutes and fading inside an hour. It is uncomfortable and not dangerous, and it is not evidence of an effective amount. Nicotinamide does not flush at all, which is why no-flush products use it. The NHS puts the amount unlikely to cause harm at 17mg a day of supplemental nicotinic acid, against 500mg a day of nicotinamide, and adults need roughly 16.5mg a day if male and 13.2mg if female from all sources. Slow-release nicotinic acid softens the flush but has been associated with more liver strain than the immediate-release form, so trading one for the other is not free.
Reference values
Daily reference values from official nutrition authorities. These are population reference figures, not personal recommendations.
| RDA | Upper limit | Source |
|---|---|---|
| 17 mg | 10 mg | UK SACN DRVs (1991) -- 17 mg NE/day; EFSA UL 10 mg/day nicotinic acid (flushing threshold). Note: UL applies to nicotinic acid only; nicotinamide and NR have no established UL. |
Forms and bioavailability
Not all forms are absorbed equally. The form on your supplement label affects how much your body can actually use.
| Form | Absorption | With food | Timing | Evidence |
|---|---|---|---|---|
| Nicotinamide (no-flush niacin) | Typical | With food | Either | Strong |
| Nicotinic acid | Typical | With food | Either | Strong |
| Nicotinamide riboside (NR) | Higher | With food | Either | Possible |
| Nicotinamide mononucleotide (NMN) | Higher | With food | Either | Possible |
Stack Almanac records which B3 form is in each product you log, so a no-flush label and a flush-inducing one are not filed under the same number.
Track your Niacin (Vitamin B3) in Stack Almanac
Last reviewed: 2026-05-25. Reference values are adult-general RDAs from UK. Individual needs may vary. This page is for informational purposes only and is not a substitute for professional medical advice.