The term biguanide refers to a group of oral diabetes medications that work by preventing the production of glucose in the liver, improving the body’s sensitivity toward insulin and reducing the amount of sugar absorbed by the intestines.

The only available biguanide medication is metformin, which is commonly used as a first-line treatment for type 2 diabetes (i.e. the first option for type 2 diabetics who are unable to control their blood sugars through diet and exercise alone).

Metformin is usually prescribed as a single treatment (monotherpay), but it can also be combined with other medication in a single tablet – for example, metformin + pioglitazone (Competact), metformin + vildagliptin (Eucreas) and metformin + sitagliptin (Janumet). It’s also sometimes prescribed in combination with insulin for people with type 1 diabetes.

Drugs in this class

As already mentioned, metformin is the only biguanide available on the market. However, there are two different versions of the drug;

  • Metformin IR (immediate-release) – taken up to three times a day
  • Metformin SR (slow release) – usually taken once per day

Metformin IR is sold under the brand name Glucophage, while the trade name for metformin SR is Glucophage SR.

metformin oral antidiabetic drug
Metformin is an oral antidiabetic drug for the treatment of diabetes.

How biguanides work

Biguanides work by preventing the liver from converting fats and amino-acids into glucose.

They also activate an enzyme (AMPK) which helps cells respond more effectively to insulin and take in glucose from the blood.

Who are biguanides suitable for?

Metformin is generally suitable for most people with type 2 diabetes as the first line of medication when lifestyle changes have not sufficiently lowered blood glucose levels.

You can take metformin on its own, as a monotherapy, or in addition to other oral or injectable diabetes medications. It may also be prescribed in combination with insulin for people with type 1 diabetes who have signs of insulin resistance.


Metformin helps lower blood glucose levels throughout the day by reducing the liver’s blood glucose-raising effect. Rather than stimulating the release of insulin, metformin increases the body’s sensitivity to insulin and therefore has benefits for weight management.

Side effects

When taken as a a monotherapy, metformin users are unlikely to experience hypoglycemia or weight gain. However, the risk of these side effects increases if the drug is taken together with insulin or the tablet medication like sulphonylureas.

Is it possible to come off metformin?

By making lifestyle changes such as regularly exercising and eating healthy foods, it is possible to reduce your blood HbA1c levels, improving your type 2 diabetes to the point you no longer need to take metformin.

Adopting a healthy lifestyle meant Gillian no longer needs to take metformin to control her condition.

For example, by following the Low Carb Program, nurse Gillian was able to lose over 30kg and no longer needs metformin to help manage her diabetes.

Find out how she did it, and read other diabetes success stories here.

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