Vitamin A

Is vitamin A safe?

At the amounts in food and a standard multivitamin, yes. As a high-dose supplement, it is one of the riskier vitamins. Preformed vitamin A, the retinol and retinyl esters in animal foods and most pills, is absorbed quickly, stored in the liver and cleared slowly. The gap between what you need and what causes harm is small: adults need 700 to 900 mcg RAE a day, and the upper limit set by the US National Academies and reconfirmed by EFSA in 2024 is 3,000 mcg RAE, or 10,000 IU.

Single-ingredient capsules of 10,000 IU sit right on that limit, and some products contain more. Add a multivitamin, cod liver oil or a weekly portion of liver and many people go over without knowing it.

Vitamin A and pregnancy

This is the main reason vitamin A scores lower than vitamin D. High intake in early pregnancy causes birth defects, mainly of the heart and nervous system. In a study of 22,748 pregnant women in the New England Journal of Medicine (1995), those who took more than 10,000 IU of preformed vitamin A a day from supplements had 4.8 times the rate of defects linked to the cranial neural crest. The authors estimated that about 1 in 57 babies of those women had a malformation caused by the supplement. The risk was concentrated in women who took it before the seventh week of pregnancy, often before they knew they were pregnant.

The NHS advises pregnant women to avoid liver and liver pâté, and to be aware of vitamin A in supplements, including fish liver oil. The Linus Pauling Institute suggests women who are or may become pregnant avoid multivitamins with more than 1,500 mcg RAE. Beta-carotene from vegetables does not carry this risk. Pregnancy multivitamins are formulated with this in mind, which is a good reason to use one instead of a general product and to take folic acid separately if needed.

Liver damage

Vitamin A is a well-documented cause of liver injuryDrug-induced liver injuryLiver damage caused by a medicine, herbal product or supplement. It is usually rare and unpredictable, but it can be serious.More in the glossary. In a series of 41 patients with vitamin A liver damage published in Gastroenterology in 1991, 17 had cirrhosis and 6 died of liver disease during follow-up. The smallest daily dose that led to cirrhosis was 25,000 IU taken for six years, a dose some people still take for skin, eyes or immunity. Heavy drinkers are at higher risk because alcohol makes the liver more vulnerable to vitamin A.

Other signs of chronic excess include dry, peeling skin, headaches, joint and bone pain and an enlarged liver and spleen. The Linus Pauling Institute says toxicity is generally associated with long-term intakes of 8,000 to 10,000 mcg RAE a day, but older people and drinkers can be affected at lower doses.

Bones are a quieter concern. Several observational studies link long-term intakes above about 1,500 mcg a day with lower bone density and more hip fractures in older adults. That is why the NHS tells people over the menopause and older men to stay at or below 1,500 mcg a day from food and supplements combined.

Beta-carotene and smokers

Beta-carotene is the plant form that the body converts to vitamin A as needed, and from food it is safe. As a pill, it failed badly in two large trials. In the ATBC trial (NEJM, 1994), 29,133 Finnish male smokers who took 20 mg of beta-carotene a day had 18% more lung cancer and 8% higher overall mortality than those who did not. The US CARET trial (NEJM, 1996) gave 30 mg of beta-carotene plus 25,000 IU of retinol to 18,314 smokers, former smokers and asbestos workers; lung cancer rose by 28% and deaths by 17%, and the trial was stopped 21 months early.

EFSA concluded in 2024 that smokers should avoid supplements containing beta-carotene, and that the general population should use them only to meet vitamin A needs.

Interactions

• Retinoid drugs such as isotretinoin, acitretin and bexarotene are related to vitamin A; taking them with a vitamin A supplement raises the risk of toxicity.
• Alcohol increases the liver toxicity of retinol.
• Orlistat, cholestyramine and colestipol reduce absorption of fat-soluble vitamins, including vitamin A.

If you take a retinoid, drink heavily, have liver disease, smoke, or are pregnant or trying to conceive, talk to your doctor or pharmacist before taking any product with vitamin A or beta-carotene.

How to check your dose

Labels use two units. 1 mcg RAE of retinol equals 3.33 IU, so 3,000 mcg is 10,000 IU and 1,500 mcg is 5,000 IU. Check whether the vitamin A in a product is retinol (acetate or palmitate) or beta-carotene; only the first counts toward the upper limit. Add up every product, especially multivitamins and fish oil made from fish liver, which often contains vitamin A.

How we scored it

Organ toxicity (50) and dose safety (58) are the weakest factors, because liver damage and birth defects occur at doses not far above the upper limit that people can buy over the counterOver-the-counterA medicine you can buy without a prescription, in a pharmacy or shop, with directions on the pack for safe use without a doctor.More in the glossary. Interactions and regulatory record (72 each) reflect retinoid drugs and EFSA's beta-carotene advice for smokers, and quality (78) is middling mainly because of confusing units and dose stacking.