Biguanides - Diabetes Medications

Definition of Biguanides - Metformin

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Biguanides are a classification of oral diabetes medication used to treat type 2 diabetes, of which metformin is the generic brand. These drugs work by affecting the production of glucose that comes from digestion. They don't cause hypoglycemia and even help with weight loss and lower cholesterol numbers. They are the most commonly prescribed drugs for type 2 diabetes. 

  • Also Known As: Metformin, Glucophage
  • Biguanides: Basics of these medications
  • Metformin: Learn more about how this drug is used.

Biguanide Medications for Diabetes

Metformin is the biguanide that is currently on the market for diabetes treatment. Glucophage (metformin) and Glucophage XR (metformin extended-release) are the most well-known of these drugs. Other registered brands include Fortamet, Glumetza and Riomet. It is also available in combination products with other diabetes drugs.

Biguanides were first derived from the French lilac, also called goat's rue, Galega officinalis. Research on its effects in lowering blood glucose levels led to the development of less-toxic derivatives. Some herbal remedies may include this plant, but if you are using diabetes medications you should use caution due to interactions.

Other types of biguanides were developed but withdrawn from the market. These include phenformin, which was introduced in 1957 at the same time as metformin but withdrawn in the late 1970's because it was associated with a high risk of lactic acidosis.

This was, unfortunately, fatal in half of the cases.

Buformin was developed in Germany in 1957 but was never sold in the United States. It also was found to have an increased risk for lactic acidosis. It was removed from the market in most countries but can still be found in some.

In addition to use for diabetes, other types of biguanides are used as antimalarial drugs, proguanil and chlorproguanil.

How Do Biguanides Work for Diabetes?

Metformin works to control the amount of sugar in your blood. It doesn't affect the amount of insulin you produce, but it increases sensitivity to insulin. This helps your cells take glucose in for their use for energy, decreases the production of glucose in the liver, and reduces the concentration of glucose in your bloodstream. The use of glucose in the intestines produces lactic acid, which is processed by the liver but can lead to the side effect of lactic acidosis. Metformin does not cause clinical hypoglycemia, which is an advantage over some other diabetes medications. It also doesn't cause weight gain and it has good effects to reduce some cardiovascular risk factors.

Metformin is often prescribed for type 2 diabetes once the disease cannot be managed by lifestyle changes alone. It is an oral medication, so it can be taken as a tablet or liquid. Depending on the form, it is taken once to three times daily. There are extended-release forms as well as forms that need to be taken with meals.

Instructions must be followed for the safe use of each product.

As diabetes progresses, insulin injections may be needed to control blood sugar and metformin may still be used to enhance the body's ability to use insulin.


Bailey CJ, "Biguanides and NIDDM," Diabetes Care, 1992 Jun,15(6)755-72.

Metformin, MedlinePlus, U.S. National Library of Medicine, 2/15/2015

Krentz AJ, Bailey CJ. "Oral antidiabetic agents: current role in type 2 diabetes mellitus." Drugs. 2005;65(3):385-411.

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