 People taking drugs should ask their health care provider or pharmacist questions about grapefruit and drug interactions.Raw grapefruit is 90% water, 8% carbohydrates, 1% protein, and contains negligible fat (table).In a 100 gram reference amount, raw grapefruit provides 33 calories and is a rich source of vitamin C (40% of the Daily Value), with no other micronutrients in significant content.