Boots WebMD Partners in Health
Return To Boots

Vitamins & minerals health centre

Vitamin B3 (niacin, nicotinic acid)

Vitamin B3 - what does it do?

Vitamin B3, also known as niacin or nicotinic acid, plays an important role in metabolism, helping the body release energy from dietary carbohydrate. Vitamin B3 also helps the body use protein and fats effectively. 

It’s essential for a healthy nervous system and also helps the body produce sex and stress hormones. It’s found in food in the form of nicotinic acid or nicotinamide, and can also be made in our body by our liver from tryptophan, a constituent of dietary protein.

Vitamin B3 uses

It’s rare to have a vitamin B3 deficiency, but it may be present in people with malnutrition and alcohol abuse. Strict vegetarians and vegans may also at risk of vitamin B3 deficiency. Low levels of niacin can lead to skin disorders, diarrhoea, indigestion and fatigue. A sore mouth, vomiting, constipation and diarrhoea may also develop with increasing deficiency. Neurological symptoms associated with deficiency include fatigue, insomnia, depression, visual impairment and memory loss.

Severe and prolonged vitamin B3 deficiency can manifest as pellagra, a skin condition most pronounced on the parts of the skin exposed to sunlight.

Vitamin B3 has been studied as a treatment for many diseases and conditions including high blood cholesterol, type 1 diabetes, intermittent claudication, the symptoms of premenstrual syndrome (PMS) and osteoarthritis.

Some of these trials used high doses of vitamin B3. Seek medical advice before taking high doses of vitamin B3 supplements for any of these conditions.

How much vitamin B3 do we need?

In the UK the adult RNI (Reference Nutrient Intake) is 17mg a day for men and 13mg daily for women.

Vitamin B3 food sources

Sources of dietary vitamin B3 include:

  • Cows milk
  • Eggs
  • UK white flour (fortified by law with no less than 1.6mg/100g flour)
  • Peanuts
  • Fresh fruit and vegetables
  • Meat, especially beef, pork,
  • Fish
  • Yeast and yeast extracts eg Marmite
  • Fortified breakfast cereals

Vitamin B3 supplements

Vitamin B3 supplements are available as a single vitamin, as part of a B group complex supplement, or within a general multivitamin and mineral supplement. The amount provided in supplements range from 0.25mg to 150mg per day in general supplements, and up to 250mg of nicotinamide as a single dose supplement.

There’s a lack of evidence for the use of Vitamin B3 supplements during pregnancy or breastfeeding. If you are pregnant choose supplements specific for pregnancy and avoid single nutrient supplements.

Vitamin B3 warnings

  • Side-effects and risks: When taken in supplement doses available on general sale side effects are rare. Nicotinic acid supplements over 50mg daily can cause uncomfortable skin flushes around the lower face and neck, a side effect that becomes more common as daily doses increase above 100mg a day.
  • High dose supplements of 3,000mg a day are linked to liver damage, gout attacks, nausea, vomiting and gastrointestinal disorders as well as skin complaints. For this reason high dose supplement use is only recommended with medical supervision. Allergies to vitamin B3 (niacin) supplements have been reported and present as skin flushing and a burning sensation.
  • Interactions: antibiotics (tetracycline), isoniazid (a drug for TB), drugs for high blood pressure, anticoagulants (blood thinning drugs), aspirin, drugs for peptic ulcer, diabetes (including metformin, insulin), nicotine patches.
  • Do not exceed the daily dose of vitamin B3 supplement. Monitor blood sugar levels if you are taking drugs for diabetes and uric acid levels if you have gout.

Dietitian reviewed by Catherine Collins RD

WebMD Medical Reference

Medically Reviewed by Dr Rob Hicks on June 29, 2015

Stay informed

Sign up for BootsWebMD's free newsletters.
Sign Up Now!

Popular slideshows & tools on BootsWebMD

woman looking at pregnancy test
Early pregnancy symptoms
donut on plate
The truth about sugar addiction
female patient consulting with female GP
Take action for a healthy baby
couple watching sunset
How much do you know?
foot being rubbed
What's causing your aching feet
smiling african american woman
Best kept secrets of healthy hair
assorted spices
Pump up the flavour with spices
woman cleaning
Cleaning tips for parents
cute baby
Caring for baby's delicate skin
woman with cucumbers on eyes
How to banish dark circles and bags
african american woman wiping sweat from forehead
Relief from excessive sweating
polka dot dress on hangar
Lose weight without dieting