Metformin: From the Perspective of a Pharmacist

If you have been in the type 2 diabetes community for any period of time, chances are, you have heard of the oral drug metformin. Metformin is a common drug used for the treatment of type 2 diabetes, and in fact, is one of the most common drugs dispensed in the pharmacy overall. The following will outline what to expect from your treatment with metformin, or perhaps if you have already been on therapy for a while, provide a refresher of the drug.

How does metformin work for type 2 diabetes?

Metformin is usually the first choice to treat high blood sugar levels in people with type 2 diabetes. In fact, it is typically prescribed at the same time that someone receives a type 2 diabetes diagnosis because it is effective for most people, has mild side effects, and is cost-effective.¹

Metformin has multiple mechanisms of action. Overall, metformin works by reducing glucose production in the liver and improving sensitivity to insulin.² Metformin can also assist with weight loss by decreasing appetite.³

How effective is metformin in reducing blood sugars?

Metformin is considered effective in lowering A1C, a test used to measure the management of blood glucose levels. A lower A1C is considered favorable, with a normal level below 5.7%.¹

In one study evaluating how well metformin works, the study group was split between people who were placed on metformin and people placed on a placebo pill (a pill that has no active drug in it). After 7 months, people in the metformin group had an A1C of 7.1% compared to people on the placebo pill, who had an A1C reading of 8.6%.³

Side effects of metformin

Every drug comes equipped with side effects. Although metformin is overall well-tolerated, there are some side effects that people should be aware of:¹

Upset stomach

This is the most common side-effect, and for most people, gets better with time. Most prescribers will initiate metformin at a very low dose to help reduce the risk for this side effect. To minimize nausea, it is advised to take metformin with food.⁴

Vitamin B12 deficiency

Vitamin B12 is an important vitamin in our body, and is found mostly in animal foods, such as meat and eggs. It is very important for the development of our brain and spinal cord and for the formation of red blood cells.⁵ Metformin can reduce the absorption of B12 in foods by up to 30%.⁶ Deficiency of B12 can result in damage to the nerves, resulting in symptoms of tingling and numbness. To help identify this before deficiency occurs, your doctor will likely routinely monitor your B12 levels. If your B12 levels are low, your doctor may suggest B12 supplementation with an over-the-counter product.

Lactic acidosis

Lactic acidosis is often cited as a rare, severe complication of metformin. Although it is very rare, it is recommended to be aware of this side effect due to the severity. When lactic acid builds up in the bloodstream, it can be very serious. However, doctors will generally not prescribe metformin in people who have a high risk for that side effect, such as those with kidney or severe liver disease.

Do you take metformin to treat your type 2 diabetes? Share your experiences below!