Does vitamin A (RAE) interact with any medications?

The weight-loss drug orlistat reduces absorption of vitamin A and can leave blood levels low.

What this means for you

The interaction that affects most people is with a weight-loss drug. Orlistat reduces the absorption of vitamin A and the other fat-soluble vitamins, and blood levels can drop as a result.

If you take orlistat, a multivitamin taken at a different time of day is the usual answer, and it is a conversation worth having with a pharmacist rather than a guess.

Not for everyone. Anyone who is pregnant or might become pregnant should treat vitamin A supplements as a medical question. High intakes of the preformed kind, and retinoid medicines, can cause birth defects, which is why the upper limit of 3,000 micrograms exists.

The second caution belongs with prescription retinoids used for acne and some cancers. Those are vitamin A in medicine form, and adding a high-dose supplement on top is how people reach the range where vitamin A causes harm rather than prevents it.

The creams have a local cost that rarely comes up at the counter.

Not for everyone. Pooling 55 studies of vitamin A derivatives put on the eye surface or the skin around it, the odds of pain were 6.4 times those on control, dryness 2.7 times, burning 2.4 times and any complaint at all 1.7 times. Serious events stayed uncommon and no commoner than on control, and the prescription strengths carried most of the harm. That is not a reason to stop a cream that is working for you. It means the stinging is a known effect rather than something you are doing wrong, and if it is bad enough to matter, the person who prescribed it can change the strength.

People sometimes reach for a single study to argue that high doses early in pregnancy turn out fine. It does not carry that weight.

Unsettled. The study followed 311 babies whose mothers took a median of 50,000 IU of vitamin A a day in the first nine weeks of pregnancy, and found no excess of major malformations. With that many babies it could only have detected a risk near three times the background rate. Read it as a study that failed to find an answer rather than one that found reassurance.

If you are on a retinoid and want to know what your own intake adds up to, the person to ask is the doctor who prescribed it. They can look at the dose you are already taking before anything else goes on top.

One practical thing follows from how vitamin A travels. It needs fat in the meal, which is the whole reason a fat-blocking drug gets in the way. Sixteen young men ate the same raw vegetable salad three ways: with no egg, with 75 g of scrambled egg, and with 150 g. With the larger amount of egg on it, the carotenoids from the salad came through three to eight times better, and most of those carotenoids are not in eggs at all.

So if a drug is already reducing how much fat you absorb, eating your vegetables dry takes away what is left. Oil, yoghurt, cheese or nuts on the salad do the same job the eggs did. That is a small thing next to the timing of the multivitamin above, and it costs nothing.

Written from the evidence cards and the data on this page, then checked back against the sources. Bioma Learn has no human medical reviewer at this time and we say so rather than invent one. Information, not medical advice. How we verify.

Full guide: Vitamin A: the supplement that increased cancer in a randomised trial