Niacinamide vs Niacin: Same Vitamin, Very Different Effects

Niacinamide and niacin are both vitamin B3, but they do not act the same. Niacin is the form that makes your skin flush and is used as a cholesterol drug. Niacinamide is the form without the flush.

I take niacinamide and I avoid niacin. Here is why, and here is where the evidence for my own reasons is thinner than I would like.

Niacinamide vs niacin: what is the difference?

• Names. Niacin is nicotinic acid. Niacinamide is nicotinamide, its amide form. The body converts nicotinic acid into nicotinamide, which is a building block for the coenzymes cells use to make energy. (Rolfe 2014)
• The flush. Niacin activates a receptor called GPR109A in skin cells. That releases prostaglandins, the blood vessels in the skin open, and you go red and hot. (Kamanna 2009) Niacinamide is known for not doing this.
• The use. High-dose niacin is a lipid drug. Niacinamide is used for skin, and as a plain B3 supplement.

What the niacin trials found

• AIM-HIGH. 3,414 patients on a statin got 1,500 to 2,000 mg of extended-release niacin a day or a placebo. HDL rose from 35 to 42 mg/dL and triglycerides fell from 164 to 122 mg/dL. Heart events did not: 16.4% against 16.2%. The trial was stopped for lack of benefit. (AIM-HIGH 2011)
• HPS2-THRIVE. 25,673 adults with vascular disease got 2 g of extended-release niacin with an anti-flush drug, or a placebo. No significant drop in vascular events. More serious side effects: new diabetes diagnoses were 1.3 percentage points higher, infections 1.4 and bleeding 0.7. (HPS2-THRIVE 2014)
• Liver. In 46 adults, 12 of the 23 who took sustained-release niacin developed liver toxicity. None of the 23 on immediate-release niacin did. (McKenney 1994)

So high-dose niacin is a drug with drug-sized risks. If a doctor has put you on it, that is between you and the doctor.

Niacinamide benefits: what the studies show

• Joints. 72 patients with osteoarthritis took niacinamide or a placebo for 12 weeks. Overall arthritis impact improved by 29% on niacinamide and worsened by 10% on placebo. A blood marker of inflammation fell by 22% and joint mobility improved. Pain scores did not change. (Jonas 1996)
• Skin, applied. 50 women put 5% niacinamide on half the face and a plain cream on the other half for 12 weeks. The niacinamide side had fewer fine lines, fewer dark spots, less redness and better elasticity. (Bissett 2005)
• Acne. A review found 10 studies. In 6 of 8 that used topical nicotinamide, acne improved. Both studies of an oral supplement showed improvement. The authors still call the effect unclear because the studies are limited. (Walocko 2017)

Where it failed

• Type 1 diabetes prevention. 552 high-risk relatives took high-dose nicotinamide or a placebo for 5 years. 82 on nicotinamide and 77 on placebo developed diabetes. No difference. (Gale 2004)
• Early Alzheimer's. 1,500 mg twice a day for 12 months raised blood nicotinamide more than 130-fold, but did not significantly lower the brain marker the trial was built around. Much of it was inactivated to methyl-nicotinamide. (Ketron 2025)

Why I take it, and what I got wrong

My reasons are metabolic. In my view niacinamide raises the NAD to NADH ratio, helps cells burn glucose and keeps free fatty acids down. Ray Peat valued it for the same reasons, and his reasoning is in Ray Peat on niacinamide.

Two corrections to my own posts.

• The trial I cited for lowering free fatty acids used acipimox, a niacin analog, in 23 patients. It cut free fatty acids by 68% and improved insulin sensitivity. It did not test niacinamide. (Hadigan 2006)
• The gut barrier study I cited used nicotinamide riboside in mice given alcohol. That is a related compound, not niacinamide, and not people. (Li 2022)

I have not read a human trial abstract showing that niacinamide itself lowers free fatty acids. So treat that part as my view and my experience.

Niacinamide dosage per day

• 500 mg twice a day for 12 months, in a skin trial of 386 people. (Chen 2015)
• 1,500 mg twice a day in the Alzheimer's trial.
• Above 3 g a day is where a safety review says nicotinamide should be treated as a drug with toxic potential, and it discourages unsupervised use. (Knip 2000)
• Around 500 mg is the level a 2025 dermatology review calls the therapeutic recommendation. It advises caution above that. (Shoukfeh 2025)

What I do: 100 to 500 mg on most days, and I would not go above 500 mg. I split it into smaller doses and always take it with carbohydrate, never fasted. Before training I sometimes take 200 to 250 mg.

Niacinamide side effects

• At 500 mg twice a day for a year: the number and type of adverse events were no different from placebo.
• In the joint trial: side effects were mild but more common on niacinamide, 40% against 27%.
• Liver and insulin: the safety review reports reversible liver toxicity at very high doses, occasional minor liver enzyme changes, and minor degrees of insulin resistance.
• Kidney patients: in dialysis patients, niacinamide caused low platelets in 4 people in one trial, and far more of them dropped out than on the standard drug. (Lenglet 2017) A larger trial at 250 to 1,500 mg a day found more low platelets, itching, anaemia and diarrhoea. (Ketteler 2023)
• Methylation: a review of high-dose nicotinamide found current use levels safe but flagged possible effects on methyl metabolism with long-term high doses. (Hwang 2020)

The honest part

• The 4PY finding. In cohorts of 2,331 and 832 people, higher blood levels of 2PY and 4PY, the end products of excess niacin, were linked to more major cardiovascular events over 3 years. For 4PY the risk was about 1.9 to 2 times higher. (Ferrell 2024) Niacinamide is broken down to 2PY as well. This is an association, and it is the best argument against taking a lot of any B3.
• The benefits are narrow. Skin, and one small joint trial from 1996.
• It failed in a 5-year diabetes prevention trial and in a 12-month Alzheimer's trial.
• My metabolic reasons are mechanism and experience, not trial results.

More is not better here. If you have kidney or liver disease, take diabetes medication or are pregnant, ask your doctor first.

Niacinamide is also one of the things I point people to for the scalp. That is in the hair loss guide. The rest of the B vitamin research is in the B vitamin studies.

Quick answers

What is the difference between niacinamide and niacin?

Both are vitamin B3. Niacin is nicotinic acid, which causes skin flushing and is used at high doses as a lipid drug. Niacinamide is nicotinamide, the amide form, which is known for not causing the flush. The body converts niacin into niacinamide.

What is a niacinamide supplement good for?

The trial evidence is for skin and joints. A 12-week trial in 72 people with osteoarthritis found a 29% improvement in overall arthritis impact, and 5% topical niacinamide improved fine lines, spots and elasticity in 50 women.

How much niacinamide per day?

Trials used 500 mg twice a day for a year and up to 1,500 mg twice a day. A safety review treats doses above 3 g a day as having toxic potential. A 2025 dermatology review advises caution above about 500 mg. The author of this article takes 100 to 500 mg.

What are the side effects of niacinamide?

At 500 mg twice a day for a year, adverse events matched placebo. Very high doses have caused reversible liver toxicity, and in dialysis patients niacinamide caused low platelets, itching and diarrhoea.

Is niacin safe?

At drug doses of 1.5 to 2 g a day, two large trials found no reduction in heart events and more side effects, including new diabetes, infection and bleeding. Sustained-release niacin caused liver toxicity in 12 of 23 people in one trial.