Millions of people take medication for heart issues, from statins for high cholesterol to beta-blockers for lowering blood pressure. However, many also turn to vitamins or minerals to improve their general wellbeing, not realising that some supplements should never be mixed with their prescribed medicines.
According to the British Heart Foundation (BHF), certain supplements can make heart treatments less effective, while others can increase side effects. The charity warns that "natural does not always mean safe," and that supplements like St John's wort, garlic and CoQ10 are not automatically risk-free.
Common supplements and heart medication risks
Figures from Which? show that around three out of four people take some form of supplement. However, the NHS states that most people do not need vitamin supplements and can get all necessary nutrients from a healthy, balanced diet, with the exception of vitamin D during autumn and winter.
Despite this, an estimated £4.1 billion is spent on dietary supplements in the UK every year. The BHF advises anyone considering starting a supplement, or already taking one, to let their doctor or pharmacist know so they can check if it is necessary and safe.
Supplements that affect blood pressure medication
The BHF says many common supplements can interfere with blood pressure medicines, including calcium channel blockers, ACE inhibitors and beta blockers. It advises that "sometimes supplements make these medicines less effective, which can cause your blood pressure to rise or fall unexpectedly."
St John's wort, a herbal supplement marketed as a natural mood booster, is well-known for causing drug interactions. It speeds up liver enzymes that break down many medicines, which can make blood pressure medicines such as amlodipine less effective. Garlic supplements, especially at high doses, could lower blood pressure more than intended when taken with prescribed medicines. Liquorice root can raise blood pressure by affecting the body's salt balance, leading to fluid retention, which can work against blood pressure medicine.
Blood-thinners and statins: what to avoid
Some supplements can interfere with blood-thinners by either increasing the risk of bleeding or increasing the risk of clots. This includes anticoagulants like warfarin, DOACs such as apixaban, and antiplatelet medicines like aspirin or clopidogrel.
Vitamin K, found in liver, Brussels sprouts, broccoli and green vegetables, can affect how warfarin works. Too much vitamin K can make warfarin less effective, while too little can mean the blood does not clot enough. Vitamin E, often promoted as an antioxidant, may increase the risk of bleeding at high doses, especially with blood-thinning medicines. St John's wort also interacts with blood-thinners by speeding up how the body breaks them down, increasing the risk of clotting. UK advice is not to take St John's wort with anticoagulants, DOACs or antiplatelets.
Omega-3 supplements, including fish oil capsules and EPA/DHA products, have shown no benefit in large clinical trials for preventing heart attack or stroke. At high doses, they may increase the risk of bleeding when taken with blood-thinners. For statins, vitamin B3 (niacin) has been linked to more side effects in some trials, including a higher risk of cardiovascular events and death. St John's wort can lower the amount of statin in the blood, making it less effective. CoQ10 has not been shown to reliably help people continue with statin treatment or reduce muscle symptoms, and vitamin D has not been shown to help with statin-related muscle aches.
