Metformin is a prescription medication used to control blood sugar levels, as an adjunct to diet and exercise, in people with Type 2 diabetes. Type 2 diabetes, or non-insulin-dependent diabetes, is the most common form of diabetes and may be treated with one or more medications. Metformin is, according to the American Diabetes Association, recommended as the starting medication and also the most widely prescribed in Type 2 diabetes. In addition to its function in blood sugar regulation, metformin has been shown to have other beneficial effects, such as helping achieve healthy cholesterol profiles and reducing breast cancer risk in diabetics.
Type 2 Diabetes
Type 2 diabetes is the most common form of diabetes and is characterized by insufficient insulin production or resistance to insulin. Sugars and starches in food are broken down into glucose, the basic sugar unit used by cells for energy. Insulin, a hormone secreted by the pancreas, promotes glucose uptake by cells, thereby reducing blood glucose levels. Even though there may be insulin produced in Type 2 diabetes patients, it is either inadequate or ineffective in reducing blood glucose. Medications, such as metformin, along with diet and lifestyle changes, are required to achieve healthy blood sugar levels in diabetics. Some Type 2 diabetics may also need insulin.
Metformin Mechanism
Metformin belongs to a class of drugs called biguanides and lowers both basal and postprandial -- after mealtime -- blood sugar. Metformin decreases glucose production by the liver and also intestinal absorption of glucose. Unlike some other diabetes medications, metformin reduces insulin resistance by promoting glucose uptake and utilization, rather than increasing insulin levels in blood -- called hyperinsulinemia. Also, metformin is typically not associated with weight gain or abnormally low blood glucose levels, side effects common in some other medications. Metformin is also prescribed to some women with polycystic ovarian syndrome -- a hormonal imbalance associated with increased risk of diabetes. Metformin and is available in tablet or solution form.
Cholesterol
Diabetics are at an increased risk of heart disease and stroke, a risk almost twice that compared to a person without diabetes. Maintaining healthy cholesterol and blood pressure levels can reduce this risk. Three types of fats contribute to the cholesterol profile- triglycerides and high- and low-density lipoprotein cholesterols, also called HDL and LDL cholesterol. HDL and LDL cholesterol are cholesterols bound by proteins called lipoproteins. Triglycerides are a lipid in blood, of a kind different than HDL and LDL cholesterol. The body converts and stores unused calories from a meal into triglycerides, and releases them later as needed. Having triglycerides at optimal levels, 100 mg/dL or lower, according to the American Heart Association, can decrease the risk of heart disease.
Effects on Triglycerides
Clinical studies have found that metformin reduces triglycerides, total cholesterol and LDL cholesterol, and raised HDL cholesterol, without any adverse effects on other lipids. A 1995 study published in "New England Journal of Medicine" found that metformin, either alone or in combination with a sulfonylurea, another kind of anti-diabetic medicine, decreased triglycerides as well as total and LDL cholesterol in Type 2 diabetes patients. Although metformin has been shown to improve the cholesterol profile in diabetics in clinical studies, it is prescribed primarily for patients who have, or who are at high risk for, diabetes rather than for cholesterol management.
Side Effects
The most common side effects of metformin are headaches, nausea and disturbances in gastrointestinal functions, such as diarrhea and indigestion. A rare but serious side effect of metformin is lactic acidosis -- buildup of too much lactate in blood. Some studies, summarized on the vitamin B-12 fact sheet compiled by the Office of Dietary Supplements, have shown that long-term use of metformin can reduce the absorption of vitamin B-12, raising the risk of vitamin B-12 deficiency. Some studies suggest that calcium supplements may improve vitamin B-12 absorption while under metformin therapy. Always consult your doctor about the benefits and harms of metformin specific to your health.
References
- Drugs.com; Metformin
- National Diabetes Information Clearinghouse; Diabetes, Heart Disease and Stroke
- American Heart Association; News Releases; April 2011
- "New England Journal of Medicine"; Ralph A. Defronzo, et al.; August 1995
- Office of Dietary Supplements; National Institute of Health; Vitamin B12
