Grapefruit powder is dehydrated whole grapefruit ground into a fine powder. It delivers vitamin C, flavonoids, and other plant compounds in a concentrated form. The drying process also concentrates furanocoumarins, the substances that famously interfere with how the body breaks down many drugs.
People stir the powder into smoothies, juice, or water for a tart citrus kick and the antioxidant content. Some take it to bump up vitamin C intake for immune support. Specific clinical evidence for the powder form itself is thin, however.
Mix a serving with liquid once a day. Taking it alongside food often eases stomach upset. Brands differ in potency, so follow the label.
Caution is critical. Grapefruit powder blocks CYP3A4 enzymes in the gut and liver, which can push blood levels of certain medications dangerously high. Do not use it without checking with your doctor or pharmacist if you take any prescription drug. This interaction is especially risky with statins, blood pressure medications, antihistamines, and immunosuppressants.