Grapefruit and grapefruit juice can be part of a healthy diet, with vitamin C and potassium in them, and while your appetite is small they may be one of the few things you want. They can also change the way some medicines work, and some prescription and over-the-counter drugs, generally ones taken by mouth, must carry a warning against eating grapefruit or drinking its juice while you take them. If you take other medicines and have never been told whether food matters with them, find out for each one by name: grapefruit juice does not affect every drug, even in the groups of medicine it is known to affect.
The kinds of medicine grapefruit can affect
Grapefruit juice can interact with some drugs in groups that include these:
- some drugs that lower cholesterol
- some drugs that treat high blood pressure
- some drugs that stop the body rejecting a transplanted organ
- some anti-anxiety drugs
- some corticosteroids that treat Crohn's disease or ulcerative colitis
- some drugs that treat abnormal heart rhythms
- some antihistamines
If one of your medicines treats a condition on the list, check that one first, since a match tells you where to begin and nothing more. Check the rest as well, because drugs outside these groups can be affected too.
What grapefruit does to a medicine, and why no safe amount fits everyone
Grapefruit juice can leave too much or too little of a drug in the body, depending on the drug, and the severity of the interaction can differ with the person, the drug and the amount of juice you drink, so how much you can have, if any, is something to find out for each drug separately.
Many drugs are broken down with the help of an enzyme called CYP3A4 in the small intestine. Grapefruit juice can block that enzyme, so instead of being broken down, more of the drug enters the blood and stays in the body longer, and with too much of a drug in the blood you may have more side effects. With certain drugs that lower cholesterol, drinking a lot of grapefruit juice may leave too much of the drug in the body, which raises the risk of liver and muscle damage that can lead to kidney failure.
With a few other drugs the effect runs the other way. Grapefruit juice can block proteins called drug transporters, some of which help move a drug into the cells that absorb it, and then less of the drug enters the blood and it may not work as well. Fexofenadine, an allergy medicine sold both on prescription and over the counter, is one such drug, and because orange or apple juice may also make it work less well, the direction on its label is not to take it with fruit juices.
The amount of CYP3A4 in the intestine varies from person to person: some people have a lot of it and some only a little. So grapefruit juice may affect two people differently even when they take the same drug, and how it acts with a drug in someone else may not be how it acts in you.
Finding out whether your medicines are affected
Ask a pharmacist or your doctor whether grapefruit juice interacts with each of your medicines, naming every one, and for each find out:
- whether that specific drug may be affected by grapefruit
- how much grapefruit juice, if any, you can have with it
- what other fruits or juices may affect it in a similar way
- whether to avoid any other foods, drinks or products, and what the possible signs of a drug interaction are, so you know what to watch for
Read the information that came with each medicine as well. For a prescription medicine that is the medication guide or patient information sheet, and you can ask the pharmacist for the package insert, which has more on possible interactions. For an over-the-counter one it is the Drug Facts label, which will say whether you should avoid grapefruit or other fruit juices with it: look under Warnings for the drug interaction and precaution information, such as when to talk to a doctor or pharmacist before use and when not to use the drug. Labels may change as new information becomes known, so read the label each time you use the medicine, even one you have bought for years.
If you have no pharmacist to ask, call the pharmacists at FDA's Division of Drug Information on 1-855-543-3784, or email [email protected], with a question about any medication.
Other fruits, foods and drinks that can affect a medicine
Grapefruit is not the only fruit involved. Pomelos, tangelos, which are a cross between tangerines and grapefruit, and Seville oranges, the kind often used for orange marmalade, might have the same effect as grapefruit juice. If one of your medicines does interact with grapefruit juice, leave those fruits out too, and check the labels of fruit juices and drinks flavored with fruit juice to see whether they are made with grapefruit juice.
Beyond fruit, a drug can react with another drug, with a food or drink, or with a medical condition you already have. Taking some medications with alcohol can result in loss of coordination, memory problems, sleepiness and falls. An herbal preparation or a supplement can also change the way another medication works (see Weight-loss supplements reach the shelf without FDA approval).
When you talk to your doctor, mention everything you take, including medicines prescribed by other doctors, over-the-counter drugs, vitamins, herbal remedies and supplements, a weight-loss one too, even the ones you use only now and then. When a doctor prescribes something new, mention the foods you eat as well, grapefruit included.
If one of your medicines turns out to be affected
When a medicine of yours is affected, follow what its label or medication guide says about grapefruit, and leave grapefruit and its juice out until the pharmacist or your doctor tells you how much you can have with that medicine, if any. Do not skip doses or stop a prescribed medicine to keep eating grapefruit without first asking your doctor, even if you feel better or think the medicine is not working: not taking it as prescribed could lead to the condition it treats getting worse, a hospital stay or even death.
Call your doctor right away if you have any problem with a medicine, or if you are worried it may be doing more harm than good, because they may be able to prescribe a different medicine or help you deal with side effects in other ways. If a side effect is uncomfortable, talk with your doctor before you stop the medicine causing it. Some medications can cause side effects that mimic other health problems, such as memory difficulties, dizziness and sleepiness, so ask your doctor whether a new problem could be caused by one of your medicines.
If your care is with NicoCares, your weight medicine is a question for your care team instead. Write to them in the Spruce messaging app to ask whether grapefruit affects it, how much you can have with it and which other fruits act the same way, and tell them there promptly about any side effect or any new medicine you start. A suspected medical emergency goes to 911 or the closest emergency room, never to a message, because NicoCares does not run emergency care.
