Herbal remedies could have affect patients at risk of heart disease.
A new report published in the Journal of the American College of Cardiology, has suggested that popular alternative medicines could have an adverse affect on heart disease treatments.
St John's wort, gingko biloba and garlic were among the herbal treatments which can interfere.
Garlic and ginkgo biloba can increase the risk of bleeding among patients taking warfarin or aspirin, while St John's wort can reduce the effectiveness of medications which control high blood pressure.
Dr Arshad Jahangir, a consultant cardiologist, commented that just because these herbal treatments are natural, does not mean they are always going to be safe.
Cathy Ross, a cardiac nurse at the British Heart Foundation, added to Dr Jahangir's sentiment: "This review highlights the problem of increasing numbers of people taking herbal medicines assuming that natural or herbal implies that they are safe.
"Many commonly used herbal or natural preparations including St John's Wort and Ginkgo will interact with medicines commonly prescribed to treat heart and circulatory disease and should be avoided."
She advised patients to check with their doctors before taking any supplements.