Can I take Fibre supplements and Losartan together?

Why this happens

Fibre supplements (like psyllium husk or methylcellulose) can act like a sponge in your digestive system. They can bind to the losartan molecules or create a physical barrier that prevents the medicine from passing through the gut wall into your bloodstream.

You do not need to stop taking either, but you should space them out. Take your losartan at least 2 hours before or 4 hours after taking your fibre supplement. Consistency is key—try to take them at the same times each day and monitor your blood pressure regularly.

Pregnancy

You must not take losartan if you are pregnant or planning to become pregnant, as it can cause serious harm or death to an unborn baby.

Choking and intestinal blockage

You must take fibre supplements with a full glass of water (at least 200ml). Taking them without enough liquid can cause the supplement to swell and block your throat or oesophagus, leading to choking or bowel obstruction.

Drug absorption interference

Fibre can prevent other medicines from being absorbed properly. Take your other medications at least 1 hour before or 2 to 4 hours after taking a fibre supplement.

High potassium levels (hyperkalaemia)

Avoid using salt substitutes containing potassium or taking potassium supplements, as losartan can cause your potassium levels to become dangerously high.

Alcohol

It is best to avoid or strictly limit alcohol when taking these supplements. Alcohol can contribute to dehydration, which increases the risk of the supplement causing constipation or a bowel blockage.

It is best to avoid or strictly limit alcohol while taking losartan. Alcohol can increase the blood pressure-lowering effect of the medicine, which may make you feel dizzy, lightheaded, or faint, especially when standing up.

Water and fluids

You must drink plenty of water (at least 200ml per dose) when taking fibre supplements. If you do not drink enough fluid, the supplement can cause a blockage in your intestine or throat.

Potassium-rich foods (e.g. bananas, spinach, salt substitutes)

Losartan can increase the levels of potassium in your blood. You should avoid using salt substitutes containing potassium (such as Lo-Salt) and speak to your doctor before significantly increasing your intake of potassium-rich foods, as high potassium levels can affect your heart rhythm.

Taking multiple medicines? Our Medicines Interaction Checker helps you check whether your prescriptions, over-the-counter medicines, and supplements are safe to take together. Simply search for your medicines to see potential interactions and what to do about them.

Disclaimer

This information is for general educational purposes only and should not be relied upon as a substitute for professional medical advice. Always consult your GP, pharmacist, or another qualified healthcare professional before making decisions about your medications. Individual circumstances may vary, and only a healthcare professional who knows your medical history can provide personalised guidance.