Hi carol! Welcome to HCM.HCG is human chorionic gonadotropin, a hormone produced during pregnancy. As a prescription medication, HCG is used mainly to treat fertility issues. On the HCG diet, you either receive injections of HCG or take HCG supplements. The HCG diet also requires you to drastically cut your calorie intake, typically consuming just 500 to 800 calories a day — about one-fourth to one-half of the standard calorie recommendations. The HCG diet is typically offered through weight-loss clinics that say they will provide medical supervision. Because the HCG diet combines injections or supplements of the HCG hormone along with severe calorie restriction, you may lose weight — at least for the short term. But it s the calorie restriction that causes the weight loss, not the HCG. In addition, the safety of HCG for weight loss is uncertain, and the hormone hasn t been approved by the Food and Drug Administration as a treatment for obesity or weight control. Severe calorie restriction can make it hard to meet all of your nutritional needs. And rapid weight loss can lead to gallstones. Also, HCG can cause side effects, including headache, fatigue, irritability and male breast enlargement. Once you stop the HCG diet, you re likely to regain any weight you lost. The key to permanent weight loss is developing healthy eating and exercise habits — not following fad diets.