Diabetes Self-Management Blog

It’s long been known, but the details have also long been sketchy: the fact that grapefruit can interact with certain prescription drugs, leading either to negative side effects or to loss of the drug’s efficacy, or both. But studies that examine grapefruit have mostly been limited to trials of individual drugs, so exactly how widespread these drug interactions are has been, to some degree, shrouded in mystery.

Even many medical professionals were surprised when, late last month, a review was released that showed adverse reactions associated with more than 85 prescription drugs. Published in the Canadian Medical Association Journal, the review looked at 161 previously published studies, most of them clinical trials of drugs, that looked at grapefruit–drug interactions. As noted in an article at MedPage Today, common adverse reactions included heartbeat irregularities, bone marrow toxicity, gastrointestinal bleeding, urine retention, dizziness, low blood pressure, and kidney toxicity — not exactly minor side effects. The study found that as little as 200–250 milliliters, or 7–8 ounces, of grapefruit juice were all that was needed to trigger a reaction. (Other types of citrus fruits, including limes, Seville oranges — a common ingredient in marmalade — and pommelos also contain the same problem chemical as grapefruit.)

Several of the drugs named in the review are especially likely to be taken by people with diabetes, including two blood-glucose-lowering Type 2 diabetes drugs, repaglinide (brand name Prandin) and saxagliptin (Onglyza). Other commonly prescribed drugs include atorvastatin (Lipitor, generic options) and simvastatin (Zocor, generic options), both lipid-lowering drugs. Other drug categories with grapefruit interactions include anticancer, anti-inflammatory, immunosuppressant, and nervous-system drugs, including many prescription painkillers. A complete list of the drugs cited in the review can be found here.

How do you feel about grapefruit — did you, or do you now, consider it risky? Have you ever had an adverse reaction from grapefruit and a prescription drug? Have you ever been told by your doctor or pharmacist that you should avoid grapefruit because of a drug you’re taking? Is there a way to enjoy it in moderation, or should everyone who takes prescription drugs avoid it, just to be on the safe side? What about other citrus fruits, where the risk is certainly lower but may be present? Leave a comment below!

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Comments
  1. It would be nice to know what exactly it is about grapefruit that causes these reactions.

    Posted by Joe |
  2. Hi Joe,

    Thanks for your question. The reactions are caused by specific chemicals in grapefruit (and certain other citrus fruits) that interfere with the enzymes that break down medicines in the digestive system.

    Best,
    Diane Fennell
    Web Editor

    Posted by Diane Fennell |
  3. Is there a difference in the adverse reaction between
    grapefruit juice or grapefruit sections?

    Posted by george salem |
  4. We do not generally eat grapefruit but do enjoy oranges, loquat, kumquat, and satsumas which are more common in the deep South at this time of year. Would they contain the ‘certain citrus fruit’ ingredient which is contained in the reactive group of citrus?

    Posted by Teresa Creal |
  5. I have a question I like oranges and I take glyburide for my type II diabetes will it affect the glyburide? I maintain my diabetes to I consider well I keep it hundred and can or below I have been as low as 60 is that dangerous how low can I go? Any help you can give me will be appreciated. Thank you

    Posted by Manuel Mora Sr. |
  6. I take theophylline and have for at least 25 years so I don’t eat grapefruit. I don’t li much either. But what are these oranges and are all oranges suspect? I take a luandry list of other things bec ause I have three auto-immune diseases and this worries me because I eat oranges all the time.

    Posted by Lynda |
  7. Very disappointed that a pharmacist never warned me about this and it isn’t in the literature. I take Ibuprofen regularly and love grapefruit. Luckily I guess my portions have always been small. I also comsume lime juice regularly. Thanks you orcnce again for always being on top of the best info.

    Posted by Gaye |
  8. Can you eat grapefruit at a different time than when you take your medication? How many hours?

    Posted by Sandy Kellogg |
  9. Hi Diane
    Until today I had heard nothing about a risk of interaction of grapefruit with drugs, and eventually oranges.
    If I must resing the citrus I will. In fact from now on no more grapefruit.

    Perhaps a meaningless question, but a period separating the intake of medicines and juices could decrease or stop these risk of interaction?

    best regards
    Juan

    Posted by Juan |
  10. It is important to note that fresh grapefruit is not as concentrated in the problematic substance. Timing of the grapefruit around medication may also be a consideration.

    Posted by Judy Shishmanian |
  11. I was reading the contents of the posted comments and I did not see any reply to them about other citrus fruit. I love oranges, tangerines, clementines, lemons, limes, etc… My simvastatin mentions grapefruit but what other citrus fruit affects my meds?

    Posted by James Carpenter |
  12. Do Kumquats contain furanocoumarins (the substance that causes interactions with statins)?

    Posted by Brian Salzberg |

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