Grapefruit juice may interfere with the enzymes that break down (metabolize) various drugs in the digestive system ‚It includes certain calcium channel blockers used to lower blood pressure and some statin/cholesterol-lowering drugs. The result can be very high levels of these drugs in your blood. Although metformin is not listed as a drug that has significant interaction with grapefruit, please consider the type and amount of sugar contained in the grapefruit product you buy and drink/eat. Because many juices have a sugar content, that could interfere with your blood sugar levels and may need monitoring. If you have additional questions about how grapefruit may interact with your medicines, please follow up with your doctor or pharmacist.