Metformin

What is metformin?

Metformin is the most common medicine used to treat type 2 diabetes in adults and children ages 10 and older. It is also used to treat gestational diabetes. Metformin is taken by mouth as a pill or liquid with meals, and most people take it long term.  

Metformin belongs to a class of medicines called biguanides. 

How does metformin work? 

Metformin helps control type 2 diabetes by:  

• Lowering the amount of glucose (sugar) you absorb from your food 
• Lowering the amount of glucose your liver makes 
• Raising your body's response to insulin, which is a hormone that controls the amount of glucose in your blood

How does metformin slow down damage to my kidneys? 

Metformin helps to lower your blood sugar to prevent or slow damage to your kidneys. High blood sugar from diabetes is one of the most common causes of kidney disease. A high amount of sugar in your blood can damage the blood vessels in your kidneys, which causes them to not work as well.  

Research has found that people with type 2 diabetes and mild to moderate kidney disease who take metformin may have a lower chance of death, heart problems and kidney failure. 

Researchers are now studying metformin as a possible treatment for kidney disease. A 2021 clinical trial showed that metformin was safe and well tolerated (did not cause severe side effects) in participants with autosomal dominant polycystic kidney disease (ADPKD). ADPKD is the less common type of polycystic kidney disease (PKD), which causes cysts to form in your kidneys and liver.  

In this research study, metformin may have slightly lowered eGFR (estimated glomerular filtration rate). eGFR is a measure of how well your kidneys are working. More research is needed to see if metformin can treat kidney disease. 

What are some common side effects of metformin?

Common side effects of metformin include:

• Feeling sick to your stomach or throwing up
• Diarrhea (frequent, loose or watery stool)
• Stomach ache
• Feeling less hungry than normal
• Metallic taste in your mouth

Can I take metformin if I have kidney disease?

Your doctor will tell you whether you can take it based on your eGFR (estimated glomerular filtration rate), which is a measure of how well your kidneys are working. You may be able to take metformin if your eGFR is 45 or higher.    

If your kidneys are not working as well, they may not be able to clear metformin out of your body. This can cause metformin to build up and lead to high levels of lactic acid in your blood, called lactic acidosis. Lactic acidosis can be life-threatening. However, research has found that taking metformin does not raise the chance of lactic acidosis in people with mild to moderate kidney disease.

It is important to talk to your healthcare provider about medication and medication management questions you have.