The UK's most-prescribed drugs, and the supplements that interact with them.

At least 16 of England's top 25 medicines have a common supplement people wouldn't think to flag.

In any pharmacy, the supplement shelf and the prescription counter are a few steps apart, and they do not talk to each other. The bottle of St John's Wort does not know you are on a statin. The fish oil does not know you take a blood thinner. Nobody at the till is going to join those dots, and the leaflet in the box rarely does either.

We wanted to see how often that gap actually matters. So we took Distil's own database of assessed supplement-medication interactions and lined it up against the medicines Britain is actually prescribed, using NHS Business Services Authority dispensing volumes for England. The result is below.

The headline: of England's 25 most-prescribed medicines, at least 16 have a common supplement we have assessed and flagged as interacting with them. Not an exotic combination. Things people buy without a second thought.

Which supplements cause the most trouble.

Looked at from the other direction, a handful of supplements account for most of the flagged pairs. St John's Wort interacts with more top-prescribed UK drugs than any other supplement we have assessed (19 pairs), because it speeds up the liver enzyme that clears a long list of common medicines, from antidepressants to the contraceptive pill. After it: 5-HTP (12 pairs), bergamot extract (11), beetroot extract (11), and omega-3 (8).

The drugs that pick up the most flags are the ones you would expect once you see them: sertraline (an SSRI, where serotonergic supplements stack), the statins, and the antiplatelet and anticoagulant drugs like clopidogrel and apixaban, where bleeding-risk supplements add up.

The honest caveats.

This is not the complete UK interaction landscape, and we are careful not to dress it up as one. It is the set of supplement-by-top-drug pairs Distil has assessed and cited to the published literature. So every number here is a floor, an "at least," not a population statistic. As our coverage grows, the counts go up.

For the same reason we deliberately do not publish a "what percentage of interactions are dangerous" figure. The pairs we assess are selected because they are worth assessing, so any such percentage would be misleading. What the data can honestly show is the pattern nobody else publishes: supplement-interaction load ranked by how often a drug is actually prescribed.

What this means for you.

Not that supplements are dangerous. Most combinations are fine, and most of the flags above are about timing and dose, not a blanket ban: take your levothyroxine four hours apart from calcium and you have solved the interaction, you have not had to choose between them. The point is narrower and more useful. A minority of combinations are genuinely worth knowing about, and right now there is no easy way to tell which bucket you are in.

That is the gap Distil's free interactions checker fills: put in what you take and what you are prescribed, and it tells you whether the combination is flagged, how serious it is, and the evidence behind it. No signup, every pair cited. If something comes up, the next step is a conversation with your pharmacist or GP, not a supplement bought blind.

The supplement aisle does not know what is on your prescription. It is worth being the person who does.