Mixing medication and common supplements or herbal remedies can cause dangerous side effects, according to a new study

Many of us rely on supplements such as omega-3 fish oil, calcium or St John’s wort to help us feel fit and healthy, but according to new research, taking them alongside medication could be causing serious harm.

The study found that more than a million people aged 65 or over might suffer from conditions including bleeding, high blood sugar levels or reduced efficiency of their medication, if they mix medication and supplements.

The study, carried out by the University of Hertfordshire and NHS improvement, looked at 149 adults over the age of 65, and looked at which supplements and medication participants took.

While many combinations are harmless, there are some that can cause health problems, including:

  • St John’s wort can stop blood pressure medications from working fully
  • Omega-3 fish oil taken with bisoprolol, a blood pressure medication, can further lower blood pressure
  • Bonecal makes levothyroxine, medication for an underactive thyroid, less effective
  • Peppermint taken with lansoprazole, which lowers stomach acid, can cause side effects
  • Gingko can make stomach acid drug rabeprazole less effective
  • Glucosamine when combined with metformin, a type 2 diabetes drug, can affect blood glucose levels

Participants were found to be taking an average of three regular prescription drugs, and around a third were also using herbal remedies or supplements at the same time. The use of herbal remedies was higher in women than in men.

The NHS states that as it’s a small study it can’t really be used as an indicator of wider problems, but there’s definitely an issue of many people assuming supplements labelled ‘herbal’ can’t have adverse effects. Of course it’s worth speaking to your pharmacist or GP if you are planning to introduce supplements into your diet.