NAD+ buying guide
Does NAD+ make you flush? Only one of these molecules does
The flush belongs to one specific form of vitamin B3, it has a known receptor, and it starts at a dose an ordinary supplement can reach. Whether your NAD+ product causes it depends entirely on which molecule is actually in it.
The flush belongs to nicotinic acid, and only to nicotinic acid
The flush is unmistakable: face, arms and chest go red and hot within about half an hour, with burning, tingling and itching, and it passes. People who have had it once ask about it before buying anything else in the vitamin B3 family, which is reasonable — and the answer depends entirely on which molecule is in the bottle.
“Niacin” is used loosely to mean two different chemicals. Nicotinic acid flushes. Nicotinamide, also sold as niacinamide, does not. NIH’s Office of Dietary Supplements puts it plainly: “Nicotinamide does not cause skin flushing and has fewer adverse effects than nicotinic acid.” Same vitamin, same textbook chapter, opposite answer to the question you came here with.
Swipe or scroll horizontally when needed to compare all columns.
| Molecule | Also called | Causes the flush? | What the source says |
|---|---|---|---|
| Nicotinic acid | niacin, in the strict sense | Yes | “Thirty to 50 mg or more nicotinic acid typically causes flushing” |
| Nicotinamide | niacinamide | No | “Nicotinamide does not cause skin flushing and has fewer adverse effects than nicotinic acid” |
| Nicotinamide riboside (NR) | Niagen and others | Not established by any evidence behind this page | The fact sheet does not address NR flushing; the GRAS notice describes NR as “a source of vitamin B3” without a flushing finding |
| Nicotinamide mononucleotide (NMN) | β-NMN | Not established by any evidence behind this page | No flushing finding in any source behind this page |
| NAD+ itself | injected, infused or oral | Not established by any evidence behind this page | The one retrospective IV study reports gastrointestinal symptoms, raised heart rate and chest pressure — and does not report flushing |
Four of these five rows are an absence of evidence, not a finding of no effect. The flush literature is about nicotinic acid, because that is the molecule prescribed at gram doses for cholesterol. Nobody appears to have asked the question of NR, NMN or NAD+, and the row says so rather than filling it in.
Source: NIH Office of Dietary Supplements, Niacin — Health Professional Fact Sheet, updated November 18, 2022. Read in a browser in September 2026, because the publisher blocks automated requests.
Read the bottom three rows of that figure carefully, because they are the honest part. Nicotinamide riboside, nicotinamide mononucleotide and NAD+ itself are not listed as non-flushing. They are listed as not established, which is a different claim. The flushing literature exists because nicotinic acid has been prescribed at gram doses for cholesterol for decades and the flush was the reason patients stopped taking it. Nobody had the same commercial reason to study it in the newer precursors, and this site could not find a source that has.
The dose it starts at
The threshold is low enough to reach by accident. NIH’s fact sheet states: “Thirty to 50 mg or more nicotinic acid typically causes flushing; the skin on the patient’s face, arms, and chest turns a reddish color because of vasodilation of small subcutaneous blood vessels.”
Thirty to fifty milligrams is roughly a multivitamin. The doses used to treat dyslipidemia are 1,000 to 3,000 mg a day, more than a hundred times the recommended intake, and at those doses the fact sheet describes more serious effects. Nicotinamide’s problems start much higher — the same source names nausea, vomiting and signs of liver toxicity at 3,000 mg a day — and none of them is flushing.
What is actually happening to the skin
The mechanism is unusually well worked out for a side effect, which is worth knowing because it explains why the obvious workarounds only half work.
| Step | Established by |
|---|---|
| Nicotinic acid releases prostaglandin D2 in people | Prostaglandins 1989, PMID 2475889 |
| The skin is the major site of that release | J Invest Dermatol 1992, PMID 1373750 |
| The receptor is GPR109A — mice lacking it do not flush at all | J Clin Invest 2005, PMID 16322797 |
| Blocking prostaglandin synthesis with aspirin does not abolish it | J Diabetes 2013, PMID 22727040 — “36-53% of participants still had some degree of symptoms” |
| A second, non-prostaglandin route exists through the TRPV1 channel | Arch Biochem Biophys 2024 review, PMID 39322100 |
Source: PubMed, read in September 2026. Each row names the study that established that step.
Nicotinic acid binds a receptor called GPR109A, sitting mostly on immune cells in the skin. That triggers release of prostaglandins — principally PGD2 — which dilate the small vessels just under the surface. The receptor’s role was settled by knockout mice: “mice lacking PUMA-G did not show nicotinic acid-induced flushing”, and the same 2005 paper concluded the effect “involves release of PGE(2) and PGD(2), most likely from immune cells of the skin”.
That is why aspirin before a dose is the standard advice, and why it disappoints. A 2013 study found that after aspirin the mean flushing scores fell significantly, but “36-53% of participants still had some degree of symptoms” — even where prostaglandin synthesis had been blocked completely. A 2024 review points at a second pathway entirely: nicotinic acid also acts directly on the TRPV1 channel, offering “a different, non-prostaglandin-based explanation”. Block one route and the other is still open.
None of this machinery is generic to the B3 family. It is a property of nicotinic acid binding a specific receptor, and it is the reason nicotinamide — one small structural difference away — does nothing of the kind.
Where the 35 mg limit comes from, and what it does not cover
There is a published upper limit for niacin, it gets quoted at supplement shoppers constantly, and almost nobody quoting it mentions what it is a limit for.
| Age | Upper intake level, supplemental niacin |
|---|---|
| Birth to 6 months | None established |
| 7–12 months | None established |
| 1–3 years | 10 mg |
| 4–8 years | 15 mg |
| 9–13 years | 20 mg |
| 14–18 years | 30 mg |
| 19 years and over | 35 mg |
The limit is set by the flush, not by toxicity: “These ULs are based on the levels associated with skin flushing.” It applies to supplemental niacin only, it covers both forms even though only one of them flushes, and “the UL does not apply to individuals who are receiving supplemental niacin under medical supervision”.
Source: NIH Office of Dietary Supplements, Niacin — Health Professional Fact Sheet, Table 3, updated November 18, 2022. Read in September 2026.
The Food and Nutrition Board’s upper intake level for an adult is 35 mg of supplemental niacin a day, and the fact sheet is explicit about where that number comes from: “These ULs are based on the levels associated with skin flushing.” It is a comfort threshold, not a toxicity threshold. The Board applied it to both forms of niacin even though only one of them flushes, on the reasoning that a limit set by flushing also keeps nicotinamide intake sensible.
Two limits on the limit. The first is in the number itself: it is a limit on supplemental niacin, not on niacin from food. The second is stated by the source outright — “the UL does not apply to individuals who are receiving supplemental niacin under medical supervision”, which is how a 1,000 mg lipid dose can be a normal prescription and 40 mg can be over the limit at the same time.
The upper limit is for niacin. It is not an upper limit for NAD+, for NMN or for NR, and applying it to them would be arithmetic on the wrong molecule. The nearest thing this site found for NR is a figure FDA attributes to the notifying company in the GRAS response — an estimate of “3 mg/kg bw/day, or 180 mg/day assuming a body weight of 60 kg” — which is ChromaDex’s own estimate as FDA describes it, not a government limit, and this page will not print it as one.
So will an NAD+ product make you flush?
The honest answer is: read the ingredient, and know that you probably cannot.
- If it contains nicotinic acid, expect flushing above roughly 30–50 mg. This is the only row in the figure above where the answer is known.
- If it contains nicotinamide, flushing is not the expected effect at ordinary doses. That is a direct statement in the NIH fact sheet.
- If it contains NR, NMN or NAD+, nothing this site could find establishes an answer either way. Reports exist; published evidence, in a form that would let anyone say “this dose, this often”, does not.
- An infusion is a different question again. The one retrospective study of intravenous NAD+ reports gastrointestinal symptoms, a raised heart rate and chest pressure during the drip, and does not report flushing. That study is covered here.
The practical obstacle is that most product pages do not tell you enough to place yourself in that list. Across the 382 NAD+ figures this site has read from 110 sellers, 127 state a dose at all — and a dose is a weaker disclosure than a molecule. Where a seller does not say which form of B3 is in the product, or how much of it, the question this page answers cannot be answered about their product. The sellers that do state a dose are on their own board.
What this page cannot tell you
Whether NR, NMN or NAD+ cause flushing. This page states that as unestablished rather than as a no, and that distinction is load-bearing: the sources cited here are about nicotinic acid, and reasoning from one molecule’s receptor pharmacology to another’s would be exactly the kind of borrowed authority this site exists not to publish. It would be settled by a controlled human study reporting flushing incidence for those compounds specifically.
It also cannot tell you what is in any particular product. Ingredient identity is a fact about a label, and this site reads price pages.
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About this page
Nothing here is medical advice, diagnosis or treatment. This is a price index, and pages like this one exist because a reader cannot judge a price without knowing what the thing is. Talk to a licensed clinician before starting or stopping anything, and see the medical disclaimer.
Document sources read September 2026. The references below retain each source reading date and the date printed on the document itself. An editorial revision does not refresh those source records. If something here is wrong, the corrections page says how that gets fixed and what has been fixed before.
Sources
- Niacin — Health Professional Fact Sheet
- Release of markedly increased quantities of prostaglandin D2 in vivo in humans following the administration of nicotinic acid.
- GPR109A (PUMA-G/HM74A) mediates nicotinic acid-induced flushing.
- Role of prostaglandin D2 and the autonomic nervous system in niacin-induced flushing.
- Niacin-induced flushing: Mechanism, pathophysiology, and future perspectives.
- Agency Response Letter GRAS Notice No. GRN 000635
- Intravenous infusion of nicotinamide adenine dinucleotide (NAD+) versus nicotinamide riboside (NR): a retrospective tolerability pilot study in a real-world setting.