When you take a medicine, your body will start to break it down using proteins called enzymes. Different enzymes break down different medicines.
The amount of medicine you take (the dose) is worked out to allow for how long this breakdown takes.
Grapefruit and grapefruit juice stops one of your enzymes from working. This means some medicines will not be broken down. Instead they can build up in your body.
When you have too much of the medicine in your body you are at risk of severe side effects. These could be very dangerous.
If you have been told not to take grapefruit, then you are probably taking one of the medicines that is known to be a problem. If you are not sure, please ask your healthcare team to confirm.
No, the effect of grapefruit on the enzyme can last more than 24 hours. So even if you only take your medicine once a day it is not safe to have grapefruit at the other end of the day.
Grapefruit juice is sometimes an ingredient in other drinks. Always check the ingredients of anything called “citrus” or “tropical”.
If you take ciclosporin avoid:
- pomelo juice
- purple grape juice.
If you take tacrolimus avoid:
- pomelo juice
- pomegranate and pomegranate juice
There is also some evidence that you should avoid the following if you are taking tacrolimus:
- Seville oranges and marmalade (jaffa, or sweet oranges and their juice are fine)
- large amounts of lime juice (a squeeze in cooking or in a drink is fine)
- large amounts of bergamot or dried citrus fruit peel
- large amounts of Earl Grey tea (have no more than 2 cups a day)
Grapefruit affects lots of drugs. This includes some immunosuppressants, statins, blood thinners, and medicines for high blood pressure, or anxiety. People taking different medicines to you might have been given different advice about grapefruit.
If you are not sure if it is safe for you to have grapefruit, you can look at the leaflet in the medicine box. Or ask your pharmacist or doctor.
There is some evidence that large amounts of liquorice might change the way some medicines work.
NHS advice is that you should not eat liquorice if you are taking a steroid called prednisolone.
Large amounts of liquorice can be bad for you even if you do not take prednisolone. Especially if you are over 40 and have a history of high blood pressure or heart disease.
But most people would need to eat a lot of liquorice for it to be a problem. More than 57g a day for at least 2 weeks.
Liquorice in herbal drinks and medicines
Some herbal medicines and drinks can contain large amounts of liquorice. If you need to avoid liquorice always check the label of these products. If you have a liver condition always talk to your doctor before trying herbal medicines. As well as the problem of mixing different medicines, you will be at higher risk of side effects from a herbal medicine.
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We would like to thank our clinical reviewer Sital Shah, Consultant Pharmacist, Hepatology, King’s College Hospital NHS Foundation Trust.
Published: January 2024
Review due: January 2027