Short answer
Grapefruit and grapefruit juice can change how much of some medicines reaches your bloodstream. According to the US Food and Drug Administration, for most affected drugs grapefruit juice blocks an enzyme in the small intestine called CYP3A4, so "the juice lets more of the drug enter the blood", and with too much drug in the blood you may have more side effects (FDA). For a few drugs, such as the allergy medicine fexofenadine, the FDA says grapefruit juice has the opposite effect: less drug enters the blood and it may not work as well.
The FDA names examples from several groups: some statins (simvastatin, atorvastatin), some blood pressure medicines (nifedipine), some organ-transplant drugs (cyclosporine), some anti-anxiety drugs (buspirone), some corticosteroids (budesonide), some heart rhythm drugs (amiodarone) and some antihistamines (fexofenadine) (FDA). A 2013 review in the Canadian Medical Association Journal (CMAJ) reports that more than 85 drugs are known or predicted to interact with grapefruit, and that 43 of them have interactions that can result in serious adverse effects (CMAJ 2013).
Two points surprise people. First, the FDA says grapefruit juice does not affect all the drugs in these groups, so the answer depends on your exact medicine (FDA). Second, according to the CMAJ review, a single glass can act long enough to affect a once-daily medicine taken at any time of day, so spacing grapefruit and the tablet apart is not a reliable fix (CMAJ 2013). The FDA advises asking your doctor or pharmacist whether your drug is affected and how much, if any, grapefruit juice you can have.
If you only found out about this after months of grapefruit at breakfast, it is not your fault. Many people are never told, and the warning is often only in the small print of a leaflet.
Why grapefruit affects medicines
The CMAJ review explains that the chemicals responsible are furanocoumarins. In the gut wall, they bind to the CYP3A4 enzyme and switch it off permanently ("irreversible inactivation"), so enzyme activity in the small intestine stays low until the body makes new enzyme (CMAJ 2013). The FDA describes the result in plain terms: instead of being broken down, more of the drug enters the blood and stays in the body longer (FDA).
For a smaller group of medicines, the FDA says grapefruit juice acts on drug transporters, proteins that help move a drug into the body's cells for absorption. In that case less drug gets in. Fexofenadine is the FDA's example, and the FDA notes that its label says, "Do not take with fruit juices," because it may also not work as well with orange or apple juice (FDA).
The size of the effect differs between people. According to the FDA, the amount of CYP3A4 in the intestine varies from person to person, so grapefruit juice may affect people differently even when they take the same drug (FDA). The CMAJ review gives an example: with a single 250 ml serving of juice, individual felodipine levels varied widely, up to eight times the level seen with water (CMAJ 2013).
The CMAJ authors also describe which drugs tend to be affected. They are taken by mouth, normally only a low to moderate share of each dose reaches the blood, and they are broken down by CYP3A4. The interaction, they write, "is drug-specific and is not a class effect" (CMAJ 2013).
Which medications should not be taken with grapefruit?
The table shows examples by group. It is not a complete list. The risk level is shown only where the CMAJ review rates it ("predicted interaction risk" in its Table 1, per CMAJ 2013); medicines named only by the FDA have no rating here. Check your own medicine's leaflet and ask your pharmacist.
| Group | Medicines named in the source (risk level per CMAJ 2013, where rated) | Possible serious effect named in the source | Source |
|---|---|---|---|
| Statins (cholesterol) | Simvastatin (very high), lovastatin (very high), atorvastatin (high) | Rhabdomyolysis (muscle breakdown) | CMAJ 2013, Table 1; simvastatin and atorvastatin also named by FDA |
| Blood pressure (calcium channel blockers) | Felodipine (intermediate), nifedipine (intermediate) | Low blood pressure, swelling of the legs | CMAJ 2013, Table 1; nifedipine also named by FDA |
| Other heart and blood pressure medicines | Eplerenone (high) | High potassium, serious heart rhythm problems | CMAJ 2013, Table 1 |
| Blood thinners | Apixaban (high), rivaroxaban (intermediate), ticagrelor (high); clopidogrel (high) | Bleeding; for clopidogrel, loss of effect | CMAJ 2013, Table 1 |
| Heart rhythm | Amiodarone (high), dronedarone (very high), quinidine (intermediate) | Dangerous heart rhythm (torsade de pointes) | CMAJ 2013, Table 1; amiodarone also named by FDA |
| Anti-anxiety and sleep | Buspirone (high), triazolam (intermediate) | Dizziness, sedation | CMAJ 2013, Table 1; buspirone also named by FDA |
| Some antipsychotics | Quetiapine (high), lurasidone (very high), ziprasidone (high), pimozide (high) | Drowsiness; for some, dangerous heart rhythm or fainting | CMAJ 2013, Table 1 |
| Immune suppressants | Cyclosporine (high), tacrolimus (high), sirolimus (high), everolimus (high) | Kidney damage; for some, effects on blood cells | CMAJ 2013, Table 1; cyclosporine also named by FDA |
| Corticosteroids | Budesonide (not rated in CMAJ Table 1) | — | FDA |
| Allergy | Fexofenadine (not rated in CMAJ Table 1; grapefruit lowers its effect) | Medicine may work less well | FDA |
| Pain (opioids taken by mouth) | Oxycodone (high), oral fentanyl (high) | Slowed breathing | CMAJ 2013, Table 1 |
| Some anti-infectives | Erythromycin (high), quinine (high), maraviroc (very high), rilpivirine (high) | Dangerous heart rhythm; for maraviroc, fainting on standing | CMAJ 2013, Table 1 |
| Urinary and prostate medicines | Tamsulosin, silodosin, solifenacin, darifenacin (all intermediate) | Dizziness or fainting on standing; for some, urinary retention or heart rhythm problems | CMAJ 2013, Table 1 |
| Cancer medicines | Many oral targeted therapies, such as crizotinib, dasatinib, erlotinib, lapatinib and nilotinib (high) | Heart rhythm problems, effects on blood cells | CMAJ 2013, Table 1 |
The CMAJ review adds that for older patients, particularly the elderly, it is recommended that grapefruit and other citrus fruits be contraindicated (not consumed) with drugs in the very high or high categories, or that a non-interacting alternative be used where available (CMAJ 2013). Whether an alternative suits you is your prescriber's decision.
Grapefruit and statins
Grapefruit and statins is the most searched combination, because statins are so widely prescribed. According to the FDA, if you drink a lot of grapefruit juice while taking certain statins, too much of the drug may stay in your body, increasing your risk for liver and muscle damage that can lead to kidney failure (FDA).
Simvastatin and lovastatin are rated very high risk in the CMAJ review. In a study it cites, a usual amount of juice (200 ml once a day for 3 days) raised simvastatin exposure to 330% of that with water (CMAJ 2013).
Atorvastatin is named by the FDA and rated high risk in the CMAJ review (FDA, CMAJ 2013).
Pravastatin, rosuvastatin and fluvastatin are listed in the CMAJ review as alternatives: it reports that pravastatin does not produce a pharmacokinetic interaction with grapefruit, rosuvastatin is eliminated unchanged, and fluvastatin is broken down by a different enzyme (CMAJ 2013).
Can I eat grapefruit with atorvastatin? The FDA's advice is to ask your doctor or pharmacist whether your drug is affected and how much, if any, grapefruit juice you can have (FDA). If grapefruit matters to you, you can ask whether a statin that does not interact is an option. Do not switch or stop a statin on your own.
MedlinePlus lists symptoms on atorvastatin for which you should call your doctor or get emergency medical help immediately, including muscle pain, tenderness or weakness; extreme tiredness; fever; dark-colored urine; yellowing of the skin or eyes; and chest pain (MedlinePlus).
Grapefruit and blood pressure medication
Grapefruit and blood pressure medication interact mainly through the calcium channel blockers felodipine and nifedipine. The CMAJ review rates both as intermediate risk, with low blood pressure and swelling of the legs as the possible effects, and names amlodipine as an alternative (CMAJ 2013). The FDA names nifedipine as an example (FDA).
Calcium channel blockers are not the only heart medicines in the table. The CMAJ review rates eplerenone, used for high blood pressure and heart failure, as high risk, because higher levels can cause high potassium and serious heart rhythm problems (CMAJ 2013). Check your own leaflet or ask your pharmacist about every blood pressure medicine you take.
Grapefruit and birth control
Grapefruit and birth control is a common worry. The CMAJ review lists ethinylestradiol, the estrogen in many combined pills, among drugs whose levels grapefruit can raise (CMAJ 2013). The sources we used do not say whether grapefruit changes how well the pill prevents pregnancy, so ask your pharmacist about your specific method.
A different, well-documented interaction involves the herbal supplement St John's wort: according to the US National Center for Complementary and Integrative Health (NCCIH), it can weaken the effects of birth control pills (NCCIH).
Why timing does not help
Can I take my medicine in the morning and have grapefruit at night? The CMAJ review describes felodipine studies: a glass of juice (200 ml) taken within 4 hours before the tablet gave the largest effect; with a gap of 10 hours the effect was about half of the maximum, and with 24 hours about a quarter. The authors conclude that a modest single amount of grapefruit "can have sufficient duration of action to affect interacting drugs that are administered once daily at any time during the dosing interval". Drinking juice repeatedly (200 ml three times a day for a week) doubled the size of the interaction for 24 hours (CMAJ 2013).
For affected medicines, the CMAJ authors point to substituting a medicine that does not interact or removing grapefruit from the diet. The FDA advises asking your doctor or pharmacist how much, if any, grapefruit juice you can have (FDA).
Which fruits and products count?
Grapefruit in any form. The CMAJ review says freshly squeezed juice, frozen concentrate and whole fruit can all reduce CYP3A4 activity, and that one whole grapefruit or 200 ml of juice is enough to cause a clinically relevant increase in drug levels (CMAJ 2013).
Juice blends. The FDA advises that if you must avoid grapefruit juice, you check the labels of fruit juices and drinks flavored with fruit juice to see whether they contain grapefruit juice (FDA).
Seville oranges, pomelos and tangelos. The FDA says these "might have the same effect as grapefruit juice" and advises not eating them if your medicine interacts with grapefruit juice (FDA).
Limes. The CMAJ review says Seville oranges, limes and pomelos also produce the interaction (CMAJ 2013).
Regular sweet oranges such as navel or Valencia, according to the CMAJ review, do not contain furanocoumarins and do not produce this interaction (CMAJ 2013). That is about the enzyme effect only: the FDA notes that fexofenadine's label says not to take it with fruit juices (FDA). For other citrus or grapefruit-based products, ask your pharmacist.
Older adults are most at risk
The CMAJ review notes that people older than 45 are the main buyers of grapefruit and receive the most prescriptions, so many people are exposed. A pronounced interaction has been shown in people older than 70, and older adults can have less capacity to compensate for excess drug levels. For example, with grapefruit, felodipine did not trigger a compensating rise in heart rate in older adults, as it did in younger and middle-aged people. The authors conclude that older people appear to be an especially vulnerable group (CMAJ 2013).
A list that keeps growing
The research group behind the CMAJ review discovered the grapefruit interaction more than 20 years before the review was published. They report that between 2008 and 2012 the number of medicines with the potential to interact with grapefruit and cause serious adverse effects rose from 17 to 43, because of new drugs and new formulations (CMAJ 2013). The serious effects they list include dangerous heart rhythms, muscle breakdown, effects on blood cells, slowed breathing, gastrointestinal bleeding and kidney damage.
This is why no printed list, including the table above, can be treated as complete. The CMAJ authors note that the features that predict an interaction (taken by mouth, low to moderate natural absorption, broken down by CYP3A4) can often be found in a drug's prescribing information, which is something your pharmacist can check (CMAJ 2013).
Grapefruit is still part of a healthy diet
None of this means grapefruit is bad for you. The FDA says grapefruit juice and grapefruit can be part of a healthy diet and that grapefruit has vitamin C and potassium (FDA). The problem is specific: certain medicines, in certain people, and the FDA notes that the severity of the interaction can differ depending on the person, the drug and the amount of grapefruit juice.
That is why the useful question is not "is grapefruit dangerous?" but "is my medicine affected, and how much, if any, can I have?" The CMAJ review names alternatives for some affected drugs, such as other statins or amlodipine instead of felodipine or nifedipine, so ask your prescriber whether that is relevant to you (CMAJ 2013).
What to do if you already had grapefruit with your medicine
Call your pharmacist and tell them the medicine, dose and how much grapefruit or juice you had. The FDA lists your pharmacist and your medicine's patient information as the places to find out whether your drug is affected (FDA).
Do not change how you take your medicine on your own, including skipping or doubling doses, unless your doctor or pharmacist tells you to.
Know the warning signs for your medicine. They are in the patient leaflet and on the medicine's MedlinePlus page; for atorvastatin, MedlinePlus lists muscle pain, tenderness or weakness and dark-colored urine among symptoms that need a doctor or emergency help immediately (MedlinePlus).
In an emergency: if someone has collapsed, had a seizure, has trouble breathing or can't be woken up, call 911 right away. If you think too much of a medicine has been taken, call Poison Control at 1-800-222-1222 — a free, confidential line that connects you to your local poison center, 24 hours a day (MedlinePlus, HRSA Poison Help).
How to check your own medicines
The FDA suggests these steps (FDA):
Ask your doctor or pharmacist whether grapefruit juice interacts with your medication, and how much, if any, you can have.
Read the medication guide or patient information sheet that comes with a prescription drug.
Read the Drug Facts label on over-the-counter medicines, which says whether you shouldn't have grapefruit or other fruit juices with it.
Check juice and drink labels for grapefruit if you must avoid it.
It also helps to tell any new prescriber if you regularly eat grapefruit or drink its juice, and to ask whether there is a medicine in the same group that is not affected.
Living with grapefruit and medicines: the questions people ask next
How much grapefruit is too much with my medicine?
It depends on the medicine, and only your doctor or pharmacist can answer it for you. The FDA advises asking how much, if any, grapefruit juice you can have with your drug (FDA). The CMAJ review warns that high amounts used in some studies "should not be interpreted to mean" that an interaction only happens with heavy use: a single usual amount (200–250 ml of juice or a whole grapefruit) can be enough (CMAJ 2013).
How long after eating grapefruit can I take my medicine?
According to the CMAJ review, with felodipine a 10-hour gap still left about half of the maximum effect and a 24-hour gap about a quarter, so a single glass can affect a once-daily drug taken at any time of day (CMAJ 2013). The sources do not give a gap that makes it acceptable; ask your pharmacist about your medicine.
Does grapefruit affect all statins?
No. The CMAJ review rates simvastatin and lovastatin very high risk and atorvastatin high risk, and lists pravastatin, rosuvastatin and fluvastatin as alternatives (CMAJ 2013). Ask your doctor whether a switch makes sense for you, and do not switch on your own.
Can I drink orange juice with my medicine?
According to the CMAJ review, sweet oranges such as navel or Valencia do not produce the grapefruit interaction, while Seville oranges and limes do (CMAJ 2013). Separately, the FDA notes that fexofenadine may not work as well with orange or apple juice and that its label says not to take it with fruit juices (FDA). Check your leaflet for any fruit juice warning.
Does grapefruit affect antidepressants or other mental health medicines?
The CMAJ table includes buspirone, triazolam and the antipsychotics quetiapine, lurasidone, ziprasidone and pimozide (CMAJ 2013). A medicine not appearing on a list does not mean it has been shown not to interact. Ask your pharmacist about your specific medicine.
Does grapefruit interact with supplements?
The FDA and CMAJ sources we used are about medicines, not supplements. What is well documented is that some supplements change how medicines work: NCCIH says St John's wort can weaken the effects of many medicines (NCCIH). Tell your pharmacist about both grapefruit and any supplements you take.
Does marmalade count?
The FDA notes that Seville oranges are often used to make orange marmalade and advises not eating Seville oranges, pomelos or tangelos if your medicine interacts with grapefruit juice (FDA). The sources do not say how much marmalade matters, so ask your pharmacist.
What about grapefruit and sleeping pills or sedatives?
The CMAJ review rates triazolam as intermediate risk, with sedation as the possible effect, and buspirone as high risk, with dizziness and sedation (CMAJ 2013). If you take any medicine for sleep or anxiety, check the leaflet or ask your pharmacist before having grapefruit.
Before you blame yourself
People who discover a grapefruit interaction after the fact often feel foolish for not knowing. But it is one of the least intuitive facts in medicine: a fruit that can be part of a healthy diet changing how strong a tablet is, for a day or more. Most people only learn about it from a leaflet in small print.
Finding out now is useful. A check with your pharmacist tells you whether your medicines are affected and what your options are.
When to see a doctor
Contact your doctor or pharmacist if you take any of the medicines listed and regularly eat grapefruit or drink its juice, if you develop symptoms listed on your medicine's leaflet, or, on a statin such as atorvastatin, if you have muscle pain, tenderness or weakness, extreme tiredness, fever or dark-colored urine, which MedlinePlus lists as reasons to call your doctor or get emergency medical help immediately (MedlinePlus).
In an emergency: if someone has collapsed, had a seizure, has trouble breathing or can't be woken up, call 911 right away. If you think too much of a medicine has been taken, call Poison Control at 1-800-222-1222 — a free, confidential line that connects you to your local poison center, 24 hours a day (MedlinePlus, HRSA Poison Help).
How to bring this up with your doctor
What to ask for, by name. "Is my [statin / blood pressure medicine / other] affected by grapefruit? Is there an alternative that isn't?"
What to bring. A list of all your medicines and doses, and how often you eat grapefruit, pomelo, Seville oranges, limes or their juices.
What to say, out loud. "I usually have [a glass of grapefruit juice every morning]. How much, if any, can I have with my medicines?"
If you're told just to avoid it. Ask: "Is there a medicine in the same group that isn't affected, so I don't have to give it up?"
How long until you notice a difference? Most supplements take weeks, not days. See how long supplements take to work, and how to tell if one is working.
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How Welltory helps — and what it cannot do
The limits first. Welltory is a general wellness product, not a medical device. It cannot detect drug levels or interactions, and it does not diagnose any condition. Your pharmacist checks interactions.
What it can do is help you notice changes after you start a new medicine or change your diet, so you have specifics to report.
Heart rate and how you feel. On the Today screen (iPhone with Apple Watch or Oura), Battery starts each morning from your resting heart rate on waking and your sleep, and Health compares today's HRV with your own average for the past 60 days (Today screen). Welltory does not alert you to an interaction; if you feel unwell, contact your doctor or pharmacist.
Tag the change. On the Today screen (iOS, with Apple Watch or Oura), when Welltory marks a stress or rest episode and asks "What happened?", tap, type or talk: "new statin", "grapefruit juice", "dizzy when standing". Over weeks, My Patterns shows which tags tend to appear with stress and recovery; some sections need a paid plan.
A record for your doctor. From the web app you can export a CSV (Dashboard → choose a chart → Export) (export guide). Patterns are associations to discuss with your doctor, not proof of an interaction.
How we made it
We based this article on US Food and Drug Administration consumer guidance on grapefruit juice and medicines and on a review of grapefruit–medication interactions published in the Canadian Medical Association Journal (2013), including its Table 1 of interacting drugs and predicted risk. Risk levels in our table are copied from that table and are shown only where it gives one. We also used MedlinePlus drug information for atorvastatin, the NCCIH fact sheet on St John's wort, the MedlinePlus page on poisoning first aid and the HRSA Poison Help page. Every source was opened again on October 21, 2026, and statements we could not match to one of these sources were removed. This article has not been reviewed by a clinician. Search questions came from what people in the United States most often ask about grapefruit and medicines. For the product section, we checked every function against the Welltory Help Center on October 21, 2026.
Made with AI tools, then edited and fact-checked by the Welltory team. See our Editorial & AI policy.
Jane Smorodnikova, co-founder of Welltory, built the methodology behind how we read physiological data.
Written by Tatsiana Yashyna.
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This article is general information from public sources (FDA, NIH, MedlinePlus, CMAJ), not a list of every interaction, and it has not been reviewed by a clinician. Interactions depend on the exact drug, dose and your health; ask your pharmacist or doctor how much, if any, grapefruit you can have, and never stop or switch a prescribed medicine on your own. In an emergency — if someone has collapsed, had a seizure, has trouble breathing or can't be woken up — call 911. If you think too much of a medicine has been taken, call Poison Control at 1-800-222-1222 (free, confidential, 24 hours a day). Welltory is a general wellness product; it does not diagnose, treat or prevent any condition and does not detect drug interactions. Sources were opened on October 21, 2026.
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Written by Jane Smorodnikova
The founder and CEO of Welltory. A recognized tech leader with two Master's degrees and experience at MIT, she has scaled Welltory to over 17 million users.
Written by Tatsiana Yashyna
Deputy COO at Welltory. With a background in medicine and years of working with health data, she translates research and real physiological signals — sleep, stress, heart rate, and hormones — into clear, evidence-based explanations that help people understand what their bodies are telling them.
References
- US Food and Drug Administration. Grapefruit juice and some drugs don't mix. https://www.fda.gov/consumers/consumer-updates/grapefruit-juice-and-some-drugs-dont-mix
- Bailey DG, Dresser G, Arnold JMO. Grapefruit–medication interactions: forbidden fruit or avoidable consequences? Canadian Medical Association Journal 2013;185(4):309–316 (Table 1). https://pmc.ncbi.nlm.nih.gov/articles/PMC3589309/
- MedlinePlus. Atorvastatin. https://medlineplus.gov/druginfo/meds/a600045.html
- National Center for Complementary and Integrative Health. St. John's wort. https://www.nccih.nih.gov/health/st-johns-wort
- MedlinePlus. Poisoning first aid. https://medlineplus.gov/ency/article/007579.htm
- Health Resources and Services Administration. Poison Help. https://poisonhelp.hrsa.gov/
