Short answer. Adults need 14 to 16 mg of niacin (vitamin B3) a day, and children aged 1 to 13 need 6 to 12 mg, according to the NIH Office of Dietary Supplements. The upper limit for supplements is 35 mg for adults and 10 to 20 mg for children. Nicotinamide does not cause flushing; nicotinic acid can from about 30 mg.
Vitamin B3 forms at a glance
| Nicotinic acid (niacin) | Nicotinamide (niacinamide) | Inositol hexanicotinate | Nicotinamide riboside (NR) | |
|---|---|---|---|---|
| What it is | The acid form; immediate or extended release (NIH ODS) | The amide form, readily bioavailable (MacKay 2012) | Six nicotinic acid molecules bonded to inositol, sold as "flush free" (MacKay 2012) | A niacin-related compound, not labeled as a niacin source (NIH ODS) |
| Absorption | Almost complete (NIH ODS) | Almost complete (NIH ODS) | On average 30% lower and highly variable (NIH ODS) | Raised blood NAD+ with dose in human trials (Trammell 2016; Conze 2019) |
| Flushing | Typical from 30 to 50 mg (NIH ODS) | None (NIH ODS) | None (NIH ODS) | None reported at 100 to 1000 mg (Conze 2019) |
Source: NIH Office of Dietary Supplements; PubMed records under Sources.
What does vitamin B3 do in the body?
Niacin, also called vitamin B3, is a water-soluble B vitamin. The name covers nicotinic acid, nicotinamide (niacinamide) and related compounds. Every tissue turns niacin into a coenzyme called NAD, which more than 400 enzymes need. NAD helps move the energy in carbohydrates, fats and proteins into ATP, the cell's energy currency, and a related coenzyme, NADP, supports the body's antioxidant systems (NIH Office of Dietary Supplements).
The body can also make some niacin. The liver converts part of the tryptophan in dietary protein to NAD, at a usual rate of about 1 mg of niacin from 60 mg of tryptophan, though the rate varies from person to person (NIH ODS). The enzymes on that route need vitamin B2, vitamin B6 and iron. Our pages on vitamin B2, vitamin B6 and L-tryptophan cover those partners.
How much niacin do children and adults need?
Because of the tryptophan route, needs are written in niacin equivalents (NE): 1 mg NE is 1 mg of niacin or 60 mg of tryptophan. For babies up to 6 months the Adequate Intake (AI) counts preformed niacin only. The Daily Value on US labels is 16 mg for adults and children aged 4 and older (NIH ODS).
| Age | Male | Female | Pregnancy | Lactation | Upper limit (UL), supplements only |
|---|---|---|---|---|---|
| Birth to 6 months (AI) | 2 mg | 2 mg | Not set; food and formula only | ||
| 7 to 12 months (AI) | 4 mg NE | 4 mg NE | Not set; food and formula only | ||
| 1 to 3 years | 6 mg NE | 6 mg NE | 10 mg | ||
| 4 to 8 years | 8 mg NE | 8 mg NE | 15 mg | ||
| 9 to 13 years | 12 mg NE | 12 mg NE | 20 mg | ||
| 14 to 18 years | 16 mg NE | 14 mg NE | 18 mg NE | 17 mg NE | 30 mg |
| 19 years and older | 16 mg NE | 14 mg NE | 18 mg NE | 17 mg NE | 35 mg |
Source: NIH Office of Dietary Supplements, Niacin fact sheet for health professionals (Tables 1 and 3).
Most people in the United States get more than the RDA from food. In 2015 to 2016 survey data, children and teens aged 2 to 19 averaged 21.4 mg a day, adult men 31.4 mg and women 21.3 mg, and only 1% of adults fell below the average requirement. In earlier survey data, 10% of supplement users reached or passed the UL (NIH ODS). If your child takes a supplement, the dose belongs to their pediatrician, who can weigh it against what your child already eats.
Which foods are high in niacin?
Poultry, beef and fish give about 5 to 10 mg per serving in a form the body uses well. Nuts, legumes and grains give about 2 to 5 mg, and many US breads and cereals have niacin added (NIH ODS). Examples from the NIH food table, not counting tryptophan:
- Beef liver, pan fried, 3 ounces: 14.9 mg
- Chicken breast, grilled, 3 ounces: 10.3 mg
- Turkey breast, roasted, 3 ounces: 10.0 mg
- Tuna, light, canned in water, 3 ounces: 8.6 mg
- Brown rice, cooked, 1 cup: 5.2 mg
- Peanuts, dry roasted, 1 ounce: 4.2 mg
- Lentils, boiled, ½ cup: 1.0 mg
Protein adds more: 3 ounces of turkey breast carries about 180 mg of tryptophan, worth about 3 mg of niacin (NIH ODS). One serving of chicken or tuna covers more than half of an adult's daily need.
Why does niacin make your face flush, and which form avoids it?
Nicotinic acid widens small blood vessels in the skin. From about 30 to 50 mg, many people notice redness on the face, arms and chest with burning, tingling or itching, often within 30 minutes. NIH calls it unpleasant rather than toxic; taking it with food or raising the dose slowly makes it milder (NIH ODS).
For meeting the RDA, nicotinic acid and nicotinamide work equally well: both are almost completely absorbed and both become NAD (NIH ODS). The forms differ in flushing and at high doses:
- Nicotinamide (niacinamide) is readily bioavailable and does not flush (MacKay 2012, PMID 22646128; NIH ODS). Most multivitamins and B-complexes use it.
- Inositol hexanicotinate is sold as "flush free". Absorption varies widely and is on average 30% lower (NIH ODS); in a small substudy of a 6-week trial it showed no evidence of being absorbed as niacin (Keenan 2013, PMID 23351578).
- Extended or sustained release nicotinic acid releases slowly to reduce flushing but carries more liver risk at high doses (see below).
Nicotinamide riboside (NR) and NMN
NR and nicotinamide mononucleotide (NMN) are niacin-related compounds the body can use to make NAD. In November 2022 the FDA ruled that NMN may not be legally sold as a dietary supplement, because it had been authorized for study as a new drug (NIH ODS). Human NR studies so far measure NAD levels and tolerability, not health outcomes. In an 8-week randomized, placebo-controlled trial in otherwise healthy overweight adults, 100, 300 and 1000 mg a day raised whole-blood NAD+ by 22%, 51% and 142% within 2 weeks, with no reports of flushing and no difference in side effects from placebo (Conze 2019, PMID 31278280). That study, like an earlier single-dose study (Trammell 2016, PMID 27721479), involved the NR supplier. An independent 2 × 6-week crossover trial in healthy middle-aged and older adults found NR well tolerated (Martens 2018, PMID 29599478). No UL has been set for NR.
Can you take too much niacin?
Yes. Niacin from food has never been linked to harm, but supplements can cause side effects (NIH ODS). The UL is set on flushing and covers both forms in supplements; it does not apply to people taking niacin under medical supervision.
At 1,000 to 3,000 mg a day, nicotinic acid can lower blood pressure enough to raise the risk of falls, cause nausea, heartburn and blurred vision, and raise blood sugar. Over months or years it can harm the liver, and slow-release forms are more likely to do this (NIH ODS). In a 1994 randomized trial of 46 adults stepping up from 500 to 3000 mg a day, 12 of 23 people (52%) on sustained release had signs of liver toxicity, compared with none on immediate release (McKenney 1994, PMID 8309029).
Nicotinamide has a wider margin: nausea, vomiting and signs of liver toxicity have been reported at about 3,000 mg a day (NIH ODS). A 2017 meta-analysis of 47 studies with 11,741 people suggested the 35 mg UL may be cautious, yet found that in healthy people taking nicotinic acid alone, major side effects appeared below 1000 mg a day (Minto 2017, PMID 28541582).
Why gram doses are a medical decision
Extended-release nicotinic acid at 500 to 1,000 mg is a prescription medicine, and NIH says that when thousands of milligrams are taken, the supplement is being used as a drug and needs medical supervision. In the largest trial, 25,673 adults already taking a statin received 2 g a day of extended-release niacin with laropiprant or a placebo for a median of 3.9 years. Major vascular events were about the same (13.2% vs 13.7%), while serious problems with blood sugar control rose by 3.7 percentage points (HPS2-THRIVE 2014, PMID 25014686). Do not start, stop or swap a prescribed niacin product on your own.
Who is more likely to run low on niacin?
Severe deficiency, called pellagra, is very rare in the US (NIH ODS). Groups more likely to fall short include people who eat very little, including those with heavy alcohol use; people low in vitamin B2, vitamin B6 or iron, who make less niacin from tryptophan; people with Hartnup disease, a rare inherited problem with tryptophan transport; and people taking isoniazid.
Signs described by NIH include a rough, sunburn-like rash on sun-exposed skin, a bright red tongue, digestive upset, headache, fatigue and memory problems. These have many causes, so they are a reason to see a doctor and get tested, not to start a supplement on your own. Blood niacin is not a reliable guide. The most sensitive test measures two niacin breakdown products in urine: in adults, more than 17.5 micromol a day suggests adequate status, 5.8 to 17.5 low status, and less than 5.8 deficiency (NIH ODS).
Does niacin interact with medicines?
- Isoniazid and pyrazinamide. These medicines resemble niacin and block the conversion of tryptophan to niacin; isoniazid can also interfere with making NAD. Extra niacin can keep status from dropping (NIH ODS). Ask the prescriber whether niacin and B6 should be checked.
- Medicines that lower blood sugar. Nicotinic acid at 1.5 g a day or more is most likely to raise blood glucose, so people on these medicines who take high-dose nicotinic acid should have their glucose monitored (NIH ODS).
Which ASDHelp products contain niacin?
Doses are copied from each label. Several give more than the UL for some ages, so add up your total and ask your doctor.
- Spectrum B Complex + Benfotiamine: 140 mg of niacin (as niacinamide and niacin) per capsule, with the other B vitamins. Label directions: 1 capsule once or twice daily; no children's dose. One capsule is 4 times the adult UL of 35 mg, and it includes some nicotinic acid, so flushing is possible.
- Formula C: 60 mg of niacin (niacinamide and niacin) per 6 capsules, in a broad multivitamin and mineral formula. Label directions: adults and children 4 years and older, 6 capsules daily with food; under 4, as directed by a healthcare professional. This is above the adult UL and 4 times the UL of 15 mg for ages 4 to 8.
- MITOboost Protein Powder Strawberry: 15 mg of niacin (as niacinamide) per scoop (29.6 g). Label directions: 1 scoop once daily in 8 to 10 ounces of liquid; no children's dose. Below the adult UL.
- Spectrum Formula Chewable + Iron: 10 mg of niacin (as niacinamide) per 4 chewable tablets, with 3 mg of iron. Label directions: ages 1 to 3, 1 to 2 tablets twice daily (5 to 10 mg); 4 and older, 2 to 4 tablets twice daily (10 to 20 mg). The top of each range reaches or passes the UL for ages 1 to 3 and 4 to 8. Keep it out of children's reach because it contains iron.
For a child, the pediatrician should choose the product and the dose.
Questions to take to your doctor
- Given how much meat, fish, grains and protein we eat, do we need any supplemental niacin at all?
- If I combine a B-complex and a multivitamin, how much niacin am I getting in total, and is that above the UL for my age or my child's age?
- Do any of my medicines, such as isoniazid or a medicine that lowers blood sugar, change what I should take?
- Is a urine niacin test worth doing?
Sources
- NIH Office of Dietary Supplements. Niacin: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Niacin-HealthProfessional/
- MacKay D, Hathcock J, Guarneri E. Niacin: chemical forms, bioavailability, and health effects. Nutr Rev. 2012. PubMed 22646128
- Keenan JM. Wax-matrix extended-release niacin vs inositol hexanicotinate. J Clin Lipidol. 2013. PubMed 23351578
- McKenney JM, et al. A comparison of the efficacy and toxic effects of sustained- vs immediate-release niacin. JAMA. 1994. PubMed 8309029
- HPS2-THRIVE Collaborative Group. Effects of extended-release niacin with laropiprant in high-risk patients. N Engl J Med. 2014. PubMed 25014686
- Minto C, et al. Definition of a tolerable upper intake level of niacin: a systematic review and meta-analysis. Nutr Rev. 2017. PubMed 28541582
- Trammell SA, et al. Nicotinamide riboside is uniquely and orally bioavailable in mice and humans. Nat Commun. 2016. PubMed 27721479
- Conze D, Brenner C, Kruger CL. Safety and metabolism of long-term administration of nicotinamide riboside chloride in healthy overweight adults. Sci Rep. 2019. PubMed 31278280
- Martens CR, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nat Commun. 2018. PubMed 29599478
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease. This article is educational and is not medical advice.