Vitamin A

What it is

Vitamin A comes as preformed vitamin A (retinol) from liver, oily fish, eggs and dairy, and as carotenoids such as beta-carotene from orange and green vegetables, which your body converts as needed.

It is needed for vision (especially in dim light), skin, immune function and growth. Deficiency is common worldwide but rare in the UK; most people get enough from diet.

Unlike many vitamins, too much can cause harm because it is fat-soluble and stored in the liver. This is especially important in pregnancy.

How it works

Retinol is converted into forms that help the retina detect light, regulate gene activity in skin and other tissues, and support immune cells. Beta-carotene is converted to retinol only as needed, so it is much less likely to cause toxicity.

What the evidence says

• Strong Correcting deficiency (night blindness, dry eyes)
  Highly effective in deficient populations.
• Strong Lowering infection deaths in deficient children
  Applies to populations with deficiency, not to the UK general public.
• Moderate Eye health in age-related macular degeneration (AREDS formula)
  A specific combination formula slowed progression in some people; it is a medical decision.
• Limited Skin health (oral supplements in healthy people)
  Prescription retinoids are different drugs; plain vitamin A pills are not a proven acne or anti-ageing treatment.
• Weak General immune boosting in well-nourished people
  No convincing benefit if you already get enough.

Evidence ratings are our plain-English summary of how much good human research exists, not a promise of results. How we rate evidence.

Dosage and timing

• NHS advice: adults should be able to get enough from diet. Taking 1.5 mg (1,500 micrograms) or more a day of retinol over many years may affect bones.
• Avoid liver and liver products (pate) more than once a week, or at all if pregnant or trying to conceive.
• If you take cod liver oil or multivitamins, check how much retinol is in each; they can stack up.
• Beta-carotene is safer for general use, but see the smoking warning below.

Forms and what to look for

• Retinol or retinyl palmitate is preformed vitamin A and carries the toxicity risk.
• Beta-carotene is a precursor and much safer for toxicity, though it can turn skin orange at high intakes (harmless).
• Mixed carotenoid products add lutein and others.
• Cod liver oil and fish liver oils contain significant retinol, plus vitamin D.

What to expect, and when

• Night vision problems from deficiency improve within days to weeks of correction.
• You will not notice anything if you are not deficient.
• Toxicity can build over months to years of excessive intake.

Side effects

• Nausea, headache, dizziness and blurred vision with too much.
• Dry, cracked lips and skin, hair loss.
• Bone and joint pain with long-term excess.
• Beta-carotene can cause harmless orange-yellow skin discolouration.

Interactions

• Retinoid medicines for acne or psoriasis (isotretinoin, acitretin): taking extra vitamin A can cause toxicity.
• Warfarin: high-dose vitamin A may increase bleeding.
• Orlistat reduces absorption.
• Alcohol and vitamin A together raise liver strain.
• Combining several multivitamin or cod liver oil products can add up.

Who should avoid it

• Pregnant women or those trying to conceive: NHS advice is not to take supplements containing vitamin A (retinol) unless advised by a doctor, and to avoid liver; high levels can harm the baby.
• Smokers and former heavy smokers should avoid beta-carotene supplements, because trials found higher lung cancer rates.
• People with liver disease or heavy alcohol use.
• Anyone on retinoid medication.
• Postmenopausal women and older adults with osteoporosis risk should watch retinol intake.

Risks and safety

• Retinol overdose can cause liver damage and raised pressure inside the skull.
• Birth defects are a recognised risk at high intakes in early pregnancy.
• Not banned in sport.
• Multiple products (multivitamin, cod liver oil, fortified food) can quietly exceed safe limits.

Buying well: quality and testing

• Check whether vitamin A is listed as retinol or as beta-carotene; the label may use micrograms RAE or IU.
• Third-party seals (NSF, USP) add confidence.
• Choose pregnancy-specific products that omit retinol.
• Avoid "megadose" vitamin A products.

Bottom line

Most people in the UK get enough vitamin A from food, and the main risk is too much, not too little. If you are pregnant, trying to conceive, or a smoker, be especially careful. When in doubt, check the label and speak to your pharmacist.