It is best known as a flavoring for food. But over the years, garlic has been used as a medicine to prevent or treat a wide range of diseases and conditions. The fresh clove or supplements made from the clove are used for medicine. Garlic is used for many conditions related to the heart and blood system.These conditions include high blood pressure, high cholesterol, coronary heart disease, heart attack, and âhardening of the arteriesâ (atherosclerosis).arlic has been used safely in research for up to 7 years. When taken by mouth, garlic can cause bad breath, a burning sensation in the mouth or stomach, heartburn, gas, nausea, vomiting, body odor, and diarrhea.