Published 6 November 2026 · Last updated 6 November 2026
Vitamin B3 · Nicotinic Acid · Nicotinamide
Niacin Flush: What Causes It, What Dose Triggers It, and the Vitamin B3 That Doesn't
The flush is not an allergic reaction and it is not a sign the product is working. It is a dose-dependent release of prostaglandin D2 under the skin, and whether you get it depends almost entirely on which of the two forms of vitamin B3 you bought.
| Nicotinic Acid Powder — the flushing form |
| Nicotinamide Capsules — the form that does not flush |
The short answer
What the niacin flush is: a warm, red, prickling sensation across the face, neck, chest and arms, caused by small blood vessels under the skin widening. It is triggered by nicotinic acid binding to a receptor on immune cells in the skin, which releases prostaglandin D2.
How long it lasts: it usually begins 15 to 30 minutes after a dose and settles within 30 to 60 minutes. It does not normally require treatment.
What dose causes it: roughly 5% of people flush at 50mg and around half at 100mg. Above 250mg a flush should be expected rather than hoped against.
Is it dangerous: the flush itself is not considered harmful, but it is the reason the published upper intake level for supplemental nicotinic acid is set at just 10mg a day for adults. Doses of 1,000mg a day and above are prescription lipid-therapy territory and are not a supplement dose.
The form that does not flush: nicotinamide. Same vitamin, same six authorised health claims, no flush — and a published upper level of 900mg a day, ninety times higher than nicotinic acid.
Which to buy: if you want the flushing form, nicotinic acid. If the flush is the thing putting you off, nicotinamide does the same nutritional job without it.
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The flushing form Nicotinic Acid Powder 99.5–100.5% BP assay. Ten pack sizes, from 50g right up to 25kg. Weigh your own serving on accurate scales. View the powder → |
Pre-weighed Nicotinic Acid 500mg Capsules One capsule is the whole 24-hour ceiling, not a starting dose. 60 to 500 capsules, vegan HPMC shell. View the capsules → |
On this page
What the niacin flush actually is
Nicotinic acid vs nicotinamide — the comparison that matters
The six authorised claims for niacin
Upper levels, and why most products sit above them
What the niacin flush actually is
Take a meaningful dose of nicotinic acid and within about twenty minutes your face, neck, chest and often your arms go red, hot and prickly. It can itch. It can look alarming in a mirror. For most people it passes inside an hour.
It is not an allergic reaction, and it is not your body expelling anything. Here is what the research actually describes.
The mechanism
Nicotinic acid binds to a receptor called GPR109A, found on Langerhans cells and other immune cells sitting in the skin. That binding causes those cells to release prostaglandin D2, a signalling molecule that makes small blood vessels widen.
More blood flows close to the surface of the skin. That is the redness and the heat. Work published in the Journal of Pharmacology and Experimental Therapeutics also found a contribution from serotonin released by platelets, which may explain the itching component that prostaglandin alone does not account for.
The clearest proof of the mechanism is a commercial one. A drug called laropiprant was developed purely to block the prostaglandin D2 receptor and was sold combined with nicotinic acid to suppress the flush. It worked on the flush — which tells you the pathway was correctly identified.
Nicotinamide does not bind that receptor in the same way, which is the single reason it does not flush. Everything else about the two molecules as a source of vitamin B3 is broadly equivalent.
What dose triggers it
The flush is dose-dependent, and the figures are more consistent than most supplement effects.
| Dose | What to expect |
| 10mg | The published upper intake level for supplemental nicotinic acid. A flush is unlikely. |
| 50mg | Roughly 5% of people flush. This is the serving we state on our own powder. |
| 100mg | Around half of people flush. Worth knowing: this is the nicotinic acid in one capsule of our NMN + Niacin Complex, so that product flushes for about half of the people who take it. |
| 250mg and above | A flush should be expected, and is often intense. |
| 500mg | The maximum we state in any 24-hour period. One of our capsules is this whole amount. |
| 1,000mg+ | Not a supplement dose. This is prescription lipid-therapy dosing, given with liver function monitoring. The NIH states that intakes at this level without a doctor's approval may cause harmful effects. |
Sensitivity varies a great deal between individuals, and the same person can respond differently on different days. Those percentages describe populations, not guarantees.
How long the niacin flush lasts
Onset is typically 15 to 30 minutes after the dose, peaking shortly after, and resolving within 30 to 60 minutes in most cases.
If a flush is severe, if it lasts beyond about 90 minutes, or if it comes with dizziness, breathlessness, swelling or a drop in blood pressure, that is not the ordinary flush. Stop taking it and speak to a healthcare professional.
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Is the niacin flush dangerous?
The flush itself is generally regarded as uncomfortable rather than harmful. But there is a detail here that almost nobody selling niacin explains, and it changes how you should read every label in the category.
The upper intake level for nicotinic acid was set using the flush itself.
The Scientific Committee on Food set the tolerable upper intake level for supplemental nicotinic acid at 10mg a day for adults, and 8mg for 15 to 17 year olds. That figure was not derived from liver damage or any other organ toxicity. It was derived from flushing.
Which is why almost every nicotinic acid product on the market — ours included — sits well above it. A 50mg serving is five times that figure. A 500mg capsule is fifty times it.
We would rather tell you that than hope you never look it up. The limit exists, it is low, it is published, and the reason it is low is the effect this whole page is about.
The concerns that are genuinely about harm rather than discomfort sit much higher up. Hepatotoxicity is rare but serious and is associated with chronic high-dose use. The CDC reports that adverse effects become markedly more common above 1,000mg a day.
That is the boundary that matters. Not 50mg. Not 500mg. 1,000mg a day and above, taken regularly, without medical supervision.
Nicotinic acid vs nicotinamide — the comparison that matters
This is the most misunderstood thing about vitamin B3, and it is the reason people end up with a product they did not want.
Both are vitamin B3. Both carry the same six authorised claims. Both count toward the same nutrient reference value. And one flushes while the other does not, with a ninety-fold difference in published upper level between them.
| Nicotinic acid | Nicotinamide | |
| Also called | Niacin, flush niacin | Niacinamide |
| Does it flush? | Yes, dose-dependent | No |
| Published upper level | 10mg/day | 900mg/day |
| Authorised GB claims | The same six | The same six |
| Nutrient reference value | 16mg NE | 16mg NE |
| Who it suits | People who specifically want the flushing form | People who want the vitamin without the flush |
Read that upper level row again. 10mg against 900mg. Same vitamin. That gap is not a difference in how useful they are — it is entirely a reflection of the fact that one of them makes you go red and the other does not.
One warning on the terminology. Search "niacin vs niacinamide" and most of what comes back is skincare, where niacinamide is a topical ingredient in serums. That is a different discussion about a different application. This page is about taking it as a food supplement.
Decided which one you want?
If the flush is the point, go nicotinic acid. If the flush is the problem, go nicotinamide.
| Nicotinic Acid Powder — 50g to 25kg |
| Nicotinic Acid 500mg Capsules |
| Nicotinamide Capsules — no flush |
The six authorised claims for niacin
These are the only statements about what niacin does that may lawfully be made in Great Britain. They are quoted below in the exact register wording, and they apply to both forms equally. A serving must supply at least 15% of the nutrient reference value — 2.4mg — for them to be used.
| “Niacin contributes to normal energy-yielding metabolism” |
| “Niacin contributes to the normal functioning of the nervous system” |
| “Niacin contributes to normal psychological function” |
| “Niacin contributes to the maintenance of normal mucous membranes” |
| “Niacin contributes to the maintenance of normal skin” |
| “Niacin contributes to the reduction of tiredness and fatigue” |
Note what is not on that list. Nothing about cholesterol, nothing about blood lipids, nothing about NAD or longevity, nothing about detoxification. Those claims are not authorised, and in the case of lipid effects the dose involved is prescription medicine dosing rather than supplementation.
You can check the register yourself on the GB Nutrition and Health Claims Register.
Upper levels, and why most products sit above them
If you have followed this far you have spotted the awkward part: the published upper level for nicotinic acid is 10mg, and the market sells it at 50mg, 100mg and 500mg.
That is not sellers ignoring a safety limit for toxicity. It is a limit derived from an effect that is unpleasant rather than dangerous, in a form of the vitamin where that effect is the whole point for the people buying it. But the number exists and you are entitled to know it before deciding what to take.
Here is the position we take on our own products, and we state it on every label and page:
Our stated position on nicotinic acid
| 50mg once daily | the serving we state |
| 500mg in 24 hours | the maximum, and one capsule is this entire amount |
| 1,000mg and above | never, without medical supervision |
If you take more than one of our B3 products, add the niacin up. Our NMN + Nicotinic Acid Niacin Complex carries 100mg of nicotinic acid per capsule. So one complex capsule plus one 500mg capsule is 600mg — over the ceiling. Five complex capsules on their own reach it exactly. Total the niacin across every pack you take, not just the one labelled niacin.
Which form should you buy?
Four products, and the choice is genuinely simple once you know the flush is the only meaningful difference.
Cheapest per serving
Nicotinic Acid Powder
99.5–100.5% BP assay, synthetic, vegan, ten pack sizes from 50g to 25kg. It is the cheapest way to buy nicotinic acid per serving, and it lets you weigh a dose well below 500mg. You need accurate scales — a 50mg serving is small and cannot be eyeballed.
View Nicotinic Acid Powder →No scales needed · highest strength
Nicotinic Acid 500mg Capsules
Pre-weighed, vegan HPMC shell, 60 to 500 capsules. Read this carefully: one capsule is the entire 24-hour maximum stated above, not a starting dose. If you have never taken nicotinic acid before, the powder lets you start far lower.
View the 500mg Capsules →If the flush is the problem
Nicotinamide Capsules
Same vitamin, same six authorised claims, no flush, and a published upper level ninety times higher. If you came to this page because you flushed and did not enjoy it, this is the one you want.
View Nicotinamide Capsules →Both ingredients in one capsule
NMN + Nicotinic Acid Niacin Complex Capsules
400mg NMN and 100mg nicotinic acid per capsule. For anyone already taking NMN who wants the flushing form of B3 in the same capsule rather than as a second pack. That 100mg is 625% of the niacin nutrient reference value.
Two things follow from the 100mg, and we would rather you knew both before you ordered. It sits exactly on the dose where around half of people flush, so expect the flush from this product. And if you take it alongside the powder or the 500mg capsules, one of each is 600mg and over our stated ceiling — so pick one route or keep the total under 500mg.
View the NMN + Niacin Complex →
Who should not take nicotinic acid
Do not take it, or speak to your GP first, if any of the following apply:
Liver disease · gout or raised uric acid · poorly controlled diabetes · active peptic ulcer · unstable angina · low blood pressure · more than a modest alcohol intake
Medicines that matter: statins, blood pressure medication, warfarin and diabetes medication.
Adults 18 and over only. Not for use during pregnancy or while breastfeeding. Take with food and a full glass of water.
Ready to choose
Same vitamin, same six claims. The only question is whether you want the flush.
| Nicotinic Acid Powder — 50g to 25kg |
| Nicotinic Acid 500mg Capsules |
| Nicotinamide Capsules — no flush |
| NMN + Niacin Complex Capsules |
| Browse all vitamins |
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Questions
What causes the niacin flush?
Nicotinic acid binds to the GPR109A receptor on immune cells in the skin, which release prostaglandin D2. That widens small blood vessels near the surface, producing the warmth and redness. Serotonin released from platelets appears to contribute to the itching.
How long does the niacin flush last?
It typically starts 15 to 30 minutes after a dose and resolves within 30 to 60 minutes. A flush lasting beyond about 90 minutes, or accompanied by dizziness or breathlessness, is not the ordinary flush and warrants medical advice.
What dose of niacin causes flushing?
Roughly 5% of people flush at 50mg and around half at 100mg. At 250mg and above a flush should be expected. Individual sensitivity varies considerably.
Is the niacin flush dangerous?
The flush itself is regarded as uncomfortable rather than harmful. It is, however, the effect used to set the tolerable upper intake level for supplemental nicotinic acid at 10mg a day. The harms that matter sit much higher: hepatotoxicity is rare but serious with chronic high-dose use, and adverse effects become markedly more common above 1,000mg a day.
Which vitamin B3 does not cause flushing?
Nicotinamide, also sold as niacinamide. It is the same vitamin, carries the same six authorised claims, and has a published upper intake level of 900mg a day against 10mg for nicotinic acid.
Are nicotinic acid and nicotinamide the same thing?
They are two forms of vitamin B3 and are not interchangeable in terms of dosing. They share the same nutrient reference value of 16mg NE and the same six authorised claims, but one flushes and one does not, and their published upper levels differ ninety-fold. Never apply a dose figure for one to the other.
Should I take niacin with food?
Yes. Take it with food and a full glass of water.
How much niacin is in a serving of your powder?
The stated serving is 50mg of nicotinic acid once daily, which is 313% of the 16mg NE nutrient reference value. The maximum in any 24-hour period is 500mg.
Does the niacin flush mean it is working?
No. The flush is a vascular response to the dose, not an indicator of nutritional effect. Nicotinamide delivers the same vitamin and the same authorised claims without producing it at all.
Can I take the NMN + niacin complex alongside your other B3 products?
Only if you total the niacin. The complex carries 100mg of nicotinic acid per capsule, so one of those plus one 500mg capsule is 600mg and over our stated 500mg ceiling. Five complex capsules on their own reach 500mg exactly. Pick one route, or keep the combined total within 500mg in any 24-hour period.
Can I take niacin with statins or blood pressure medication?
Speak to your GP or pharmacist first. Statins, blood pressure medication, warfarin and diabetes medication are all relevant, and nicotinic acid can affect blood pressure in its own right.
Sources
How this article is written
Dose and upper-level figures are taken from the published sources listed above. Health claims are quoted in the exact wording of the GB Nutrition and Health Claims Register and apply to niacin as a nutrient, not to either form specifically.
No claim is made anywhere on this page about blood lipids, cholesterol, NAD, longevity or detoxification. None of those is authorised, and the lipid effects of nicotinic acid occur at prescription medicine dosing rather than at supplement intakes.
Charge Products has supplied supplements and raw ingredients from Southend-on-Sea since 2016.
Food supplement. Not a substitute for a varied and balanced diet or a healthy lifestyle. Do not exceed the stated dose. Keep out of reach of young children. Adults 18 and over only. Not for use during pregnancy or while breastfeeding.
Nothing on this page is medical advice. If you take prescription medication or are under medical supervision, speak to your doctor or pharmacist before use.
Charge Products is a trading name of Big Idea Services Ltd, Company No. 11645389. Unit 1, 8 Towerfield Road, Southend-on-Sea, Essex SS3 9QE. 5 Star Food Hygiene Rating.
