How you take medication affects how your body absorbs the active ingredients and influences how well the medication works. While some medications should be taken with food, you should heed your doctor's instructions about foods to avoid. If you enjoy a glass of grapefruit juice for breakfast, you shouldn't use the juice to wash down certain medications, including warfarin and some blood pressure medications.
Grapefruit Juice and Medication
Grapefruit juice causes some medications to dissolve and be absorbed more quickly. You could end up with too much of the medication in your body too soon, so blood pressure medication might lower your blood pressure too far. For some drugs, drinking a little grapefruit juice may not do any harm, especially if you drink the juice separately from taking medication. Check with your doctor if you regularly consume grapefruit juice.
Warfarin, sold under the brand name Coumadin, is a blood thinner that helps prevent blood clots. While drinking quantities of grapefruit juice daily can affect the performance of warfarin, Stanford University Medical Center reports that drinking 8 oz. of juice or less daily does not adversely affect the drug's performance.
Blood Pressure Medication
Some blood pressure medications enter the bloodstream too quickly if you drink grapefruit juice with them. These include nifedipine, nicardipine, felodipine, nisoldipine, nimodipine and isradapine. If you take any of these medications, ask your doctor if you should avoid grapefruit juice.
Grapefruit juice is low in calories and fat and contains vitamin C and potassium, making it a healthy addition to most diets. Since many medications don't react with grapefruit juice, don't avoid drinking it unless your doctor tells you to do so. If you have to give up grapefruit juice, you can substitute orange juice, which doesn't interact with medications.