Grapefruit and grapefruit juice may interact with diltiazem and lead to unwanted side effects. Discuss the use of grapefruit products with your doctor.
Diltiazem may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.
Avoid drinking alcohol while taking diltiazem.
Avoid taking herbal supplements containing St. John's wort at the same time you are taking diltiazem.