Does vitamin C interact with any medications?

People having chemotherapy or radiation should ask their oncologist before taking vitamin C supplements, especially in high doses.

What this means for you

For most people vitamin C does not interact with anything in a way that changes what they should do. There is one situation that does.

Not for everyone. People having chemotherapy or radiation should ask their oncologist before taking vitamin C supplements, especially in high doses. The concern is that antioxidants could interfere with treatments that work partly through oxidative damage.

Beyond that, the sensible cautions are about dose rather than drugs. High intakes raise oxalate in urine, which matters if you have formed a kidney stone before. And a supplement of a few hundred milligrams does everything a gram does, because absorption drops as the dose rises.

One interaction runs the other way and is useful rather than risky. Vitamin C taken with a meal improves how much iron your body pulls out of plant food, which is why iron tablets are often taken with orange juice. If you are on iron for a confirmed deficiency, that pairing is worth using on purpose.

A practical note on where vitamin C goes missing. It dissolves in water and breaks down in heat, so long storage and long cooking cost you more than any medicine does. In broccoli, every domestic cooking method tested except steaming caused significant losses. Five varied servings of fruit and vegetables a day can still supply more than 200 mg, which is twice the requirement, as long as some of it is raw or lightly cooked.

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 C: what it does, how much you need, and what it will not do