February is National Grapefruit Month, but before you down a glass of the juice in celebration, be sure to check whether it’s safe to pair grapefruit with the medication you take. Both grapefruit juice and the fruit itself can interact with more than 50 drugs—such as cholesterol-lowering statins, high blood pressure medications, and allergy drugs—raising the risk of side effects and other problems. Here’s how to know if you can safely enjoy grapefruit with your medication.

Grapefruit and medication could cause problems in two ways. First, grapefruit can block a key drug-metabolizing enzyme in your body, which in turn could lead to an increase in the blood levels of certain drugs. If that happens, it increases the risk of experiencing a side effect from that drug. On the flipside, it can also block absorption of certain drugs in your intestines. In that case, you could have less of the drug in your bloodstream than what you need, so the drug might not be effective for its intended purpose.

Surprisingly, it doesn’t take much of the fruit for a grapefruit and medication interaction to happen: As little as 1 cup of juice or two grapefruit wedges can be enough to cause problems, according to the Food and Drug Administration.

If you regularly eat grapefruit or drink its juice, find out if your medication interacts with the fruit, says David Bailey, Ph.D., a pharmacologist at the University of Western Ontario who first identified the dangerous interaction of grapefruit and medications. A phrase such as “Do not take with grapefruit” should be on the label or package insert that came with your medication, but you can also ask your physician or pharmacist, Bailey says.

Watch out for These Grapefruit and Medication Interactions

Medications that pose an interaction risk include:

• Some statins, such as atorvastatin (Lipitor and generic), pravastatin (Pravachol and generic), and simvastatin (Zocor and generic).

• The high blood pressure medication nifedipine (Afeditab, Procardia, and generic).

• The organ transplant rejection drug cyclosporine (Neoral, Sandimmune, and generic).

• The anti-anxiety drug alprazolam (Xanax and generic).

• The anti-arrhythmia drug amiodarone (Cordarone, Nexterone, and generic).

• The allergy medication fexofenadine (Allegra).

If there’s an interaction risk with your medication, one option is to stop eating the fruit or drinking the juice while you are on the drug, Bailey says. The FDA also recommends skipping tangelos and Seville oranges (used to make orange marmalade) because those affect the same enzyme as grapefruit juice.

Another option is to ask your physician whether there is an alternative medication that doesn’t interact with grapefruit.

If you find out that a medication you’ve already started taking poses an interaction risk, talk to your doctor before stopping it, because that could cause a sudden drop in the levels of medication in your blood.

Editor's Note: These materials were made possible by a grant from the state Attorney General Consumer and Prescriber Education Grant Program, which is funded by a multistate settlement of consumer fraud claims regarding the marketing of the prescription drug Neurontin (gabapentin).

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