Taking these supplements alongside this blood-thinning medication could increase your risk of side effects.
Nearly one million Brits have been warned about the potential dangers of mixing certain supplements with their prescribed medication. An expert has cautioned that combining these pills could be “harmful”.
A dietitian highlighted three commonly used supplements that could pose a risk when taken in conjunction with warfarin, a blood-thinning medication frequently prescribed by doctors. It’s estimated that around 1.5 per cent of the UK population, or roughly 700,000 people, are currently taking warfarin.
Victoria Taylor, a dietitian for the British Heart Foundation (BHF), advised that maintaining a healthy, balanced diet is always preferable to relying on supplements. Writing for Heart Matters, she said: “Many different supplements are available in the shops and on the internet, some of which make claims about improving general health and specific conditions like heart disease. But these claims are not always true.”
Additionally, she cautioned: “Taking a supplement cannot undo the negative effects of an unhealthy diet. Research also shows that supplements do not help to stop or improve heart and circulatory diseases. In some cases, supplements can even be harmful.”
She also challenged the widespread belief that supplements are superior due to their elevated concentrations of vitamins and minerals. She explained: “You may think supplements are healthier than food because they contain high levels of vitamins and minerals. But more is not always better. Having too much of some vitamins and minerals can be bad for your health.”
Combining supplements with warfarin
Victoria emphasised the potential dangers of combining certain supplements with warfarin, specifically highlighting vitamin K, omega-3, and St John’s wort. “Some supplements can also affect the medicines you are taking, causing side effects,” she cautioned.
“For example, vitamin K, omega-3 and St John’s wort all interact with the blood-thinning drug warfarin.” The NHS has similarly recommended care when pairing some herbal treatments with warfarin.
Its official guidance warns: “Do not take St John’s wort, the herbal remedy for depression, while you’re taking warfarin. It can increase your risk of side effects.”
Additionally, the health service suggests speaking with a GP before taking vitamin K if already prescribed warfarin. The NHS advised: “Tell your doctor if you’re taking vitamin K supplements before you start taking warfarin. Do not start taking vitamin K supplements while you are taking warfarin without checking with your doctor first.”
NICE has raised particular concerns about the heightened bleeding risk when warfarin is combined with omega-3-acid ethyl esters. It stated: “Warfarin causes bleeding, as can omega-3-acid ethyl esters; concurrent use might increase the risk of developing this effect.”
The manufacturer’s guidance also recommends caution or complete avoidance of such combinations. For those contemplating incorporating supplements into their wellness regime, Victoria suggests seeking GP consultation before taking any steps, emphasising the importance of professional guidance.
She recommended: “Talk to your doctor before spending money on supplements. If you need them they will prescribe or recommend them.” She noted that the only routine vitamin supplement universally suggested is vitamin D.
Victoria elaborated: “The exception to this is that it is recommended we all take 10 micrograms a day of vitamin D supplement in the autumn and winter, because vitamin D is mainly made in our bodies with the help of sunlight.
“Just a little comes from food. Apart from this, a healthy, varied, balanced diet provides all the energy, vitamins and minerals you need.”