You may not realise that a seemingly "harmless" supplement could interfere with a drug you take12:54, 02 Jun 2026A doctor has issued a warning about taking certain supplements as they could “interfere” with your medications. You should always check with your doctor first due to possible health risks.‌Many people take supplements as a way to ensure their bodies are getting all the nutrients they need to function to the best of their ability. While this is usually fine, there are some potential side effects that can occur when you mix these with drugs.‌With this in mind, Doctor Amir Khan explained some common pairings you should avoid. Speaking in a video uploaded to his Instagram, the ITV doctor, explained: “Over-the-counter supplements are super popular and if you’re taking them, that’s OK but remember to mention them to your doctor if you are being prescribed medication in case there is an interaction.‌“Here are some common ones. Let's have a quick chat about supplements because loads of people take them.“Magnesium, turmeric, St John's wort, collagen, herbal remedies, and I think many assume, ‘Well it's natural, so it should be safe’“But natural doesn't automatically mean harmless, especially if you're taking medication.”‌Content cannot be displayed without consentSt John’s wortSt John's wort is a herbal remedy made from the flowers and unopened buds of the plant. It is a popular complementary therapy for mild to moderate depression.But Dr Amir argued that this is one of the “biggest culprits” when it comes to medication interactions. He advised that this should not be taken with a number of different drugs.‌“For example, St John's wort, which some people take for low mood, is one of the biggest culprits,” he said. “It can interfere with antidepressants, the contraceptive pill, blood thinners, and even some medication used after organ transplant.“It changes how your liver processes drugs.”‌Turmeric or curcuminDr Amir urged people not to take this alongside blood thinners. He said: “Then there's turmeric or curcumin supplements. These are really popular for inflammation and joint pain.“But if you're taking blood thinners like warfarin or anticoagulants, there's concern about increased bleeding risk.”Magnesium“Magnesium supplements can affect how well some medications are absorbed, things like certain antibiotics or thyroid medication, so timing can matter”, Dr Amir said. “Make sure you mention that to your doctor.”‌CalciumAccording to Dr Amir, calcium supplements can do “something similar”. He warned they can reduce the absorption of medications, including levothyroxine and some antibiotics if taken together.Vitamin KVitamin K is important for bone health but he explained that this could be risky to take alongside warfarin. He said: “It can interfere with warfarin because warfarin affects your vitamin K pathways and that can affect your bleeding and clotting risk.”Article continues belowGrapefruit juiceFinally, he said that grapefruit juice, while not a supplement, should be avoided when taking certain medications. He said: “I know it isn't technically a supplement but it can interact with some statins and other medications because of the way it affects drug breakdown.”Dr Amir added: “Now, this doesn't mean supplements are bad - some are genuinely helpful for the right person at the right dose for the right reason. But my message is simply this: if you're taking regular medication, don't forget to tell your doctor which supplements you also take because sometimes the interaction we're worried about isn't between two medications, it can be between medicine and something you thought was harmless like a supplement - just let us know.”