Grapefruit can interfere with your medications — here's what you need to know

Before you dive into that grapefruit or drink a cup of grapefruit juice, you may want to check the label of any medications you may be taking. That's because the popular citrus fruit shouldn't be combined with certain medications.

Mandy Leonard, a pharmacotherapy specialist at the Cleveland Clinic, tells Yahoo Life there are naturally occurring chemicals and compounds found in grapefruits that can interact with a variety of medications. "There are certain substances in grapefruit juice and grapefruit that may affect the way the body handles a medication," says Leonard. "This can result in fluctuating levels of a medication in the body."

So how does grapefruit affect medications?

More than half of all medications are metabolized in your small intestine by an enzyme commonly known as CYP3A4. However, just a single glass of grapefruit juice can block this enzyme and interfere with your body's process of breaking down the medication. "This causes medication levels to remain higher and longer than without grapefruit," Joy Peterson, a clinical pharmacist at Wellstar Health System, tells Yahoo Life. "The increased levels may cause patients to experience side effects."

For example, when the blood pressure drug felodipine is taken with grapefruit juice rather than water, levels of the medication in the blood can more than double and result in headache, irregular heartbeat, swelling, and fluid retention. "In some instances, too much of a drug in your body long term may lead to liver damage and kidney failure," registered dietitian Keri Gans tells Yahoo Life.

Blood pressure drugs aren't the only commonly prescribed medications that grapefruit juice can mess with — they also include anticoagulants that help prevent blood clots, organ-transplant rejection drugs, and certain antianxiety medications. It's important to note, however, that grapefruit does not affect all drugs within these general categories — only certain ones. That's why it's important to find out from your health care provider or a pharmacist if any of your medications interact with grapefruit.

In addition, grapefruit can have the opposite effect on certain antihistamines, such as Allegra. These allergy medicines are absorbed into our body's cells through proteins known as transporters. But grapefruit juice blocks these transporters and as a result, lowers the amount of medicine your body gets and renders the drug less effective.

How much grapefruit is safe?

To make things trickier, the severity of how this citrus fruit interacts with medications can vary depending on the person and on the drug. "There are some case reports of people having problems with smaller amounts of grapefruit or grapefruit juice per day," says Peterson.

Still, says Peterson, "most people won't have issues unless they eat large quantities of grapefruit, drink more than one liter per day of grapefruit juice, or consistently eat or drink grapefruit. The symptoms seen with the interaction vary from medication to medication — the symptoms are not from the grapefruit. They're from the medication."

Spacing out your grapefruit intake and when you take your medications is not necessarily the best solution. That's because the negative interactions between the citrus and your medications can last up to seven days after consuming grapefruit.

How to protect yourself

Your easiest line of defense is to simply read the label on your medicine bottle. Many of them now indicate if fruit juices should be avoided. And since grapefruits are a hybrid mix of sweet orange and the Southeast Asian pomelo, there may be other fruit juices you should avoid as well. "According to the FDA, Seville oranges and tangelos may interact the same way that grapefruit does on certain medications," says Gans.

It's also a good idea to read the paperwork that comes with your prescriptions. "The best way to monitor for a grapefruit medication interaction is to look out for the side effects of the drug," says Peterson "They should be listed in your paperwork from your prescription and mentioned as part of your discussion with your pharmacist."

But if you're still not sure if your grapefruit habits may be messing with your medications, Leonard says the best advice is to talk to a trusted health care provider or pharmacist. "Many food-drug interactions and potential side effects can be avoided by following certain precautions set by your doctor, pharmacist, or dietitian," says Leonard. "Decreasing food-drug interactions can help make sure that your medications work properly."

And for those die-hard grapefruit fans, all is not lost. Gans suggests exploring some alternatives: "The nutrients found in grapefruit, such as vitamin A, C, and potassium, can easily be found in other fruits, such as cantaloupe, mango, papaya, berries, and apricots."

Want lifestyle and wellness news delivered to your inbox? Sign up here for Yahoo Life’s newsletter.