Can You Take Metformin If You Have Kidney Problems?

One of the most popular diabetes medications is metformin. It’s an effective treatment to lower hemoglobin A1C — known as A1C, a measure of your average blood glucose over the past several months — while also offering some other benefits.

Questions often come up about metformin and its effect on the kidneys — especially because many people with diabetes also have chronic kidney disease (CKD). So, can you take metformin if you already have kidney problems? And will metformin hurt your kidneys if they are healthy?

There’s a lot of misinformation out there. So let’s clear up the confusion and go over what you should know about taking metformin safely.

What is metformin?

Metformin is often the first-choice oral medication for Type 2 diabetes. It’s also prescribed off-label for:

• Prediabetes

• Gestational diabetes

• Polyendocrine metabolic ovarian syndrome (PMOS), formerly known as polycystic ovarian syndrome (PCOS)

Metformin works in a few ways to improve blood sugar and insulin resistance. It helps:

• Lower the amount of glucose made by the liver

• Improve your body’s response to insulin

• Lower the amount of glucose you absorb from food

On its own, metformin is available as immediate-release (IR) and extended-release (ER) tablets and an oral solution. It’s also available in several different combination pills with other diabetes medications. 

Metformin dosages vary from person to person. But you’ll typically take metformin once or twice a day. Larger dosages may be divided into 3 daily doses. The maximum dosage of metformin is usually 2,000 mg to 2,550 mg per day. 

Your dosage will likely be lower if you have kidney problems, which we cover in more detail later in this article.

Does metformin harm your kidneys?

No, metformin hasn’t been shown to cause kidney problems or make them worse. The kidneys help clear metformin from your body after it has done its job, but they aren’t harmed in the process. Your kidneys must be working normally to effectively get rid of metformin though.

Can you take metformin if you have kidney problems?

Yes, people with kidney problems can take metformin. But the dosage may need to be adjusted in accordance with your kidney function. And people with severe or advanced CKD may need to balance the risks and benefits of taking metformin with their healthcare team.

If you have kidney problems, metformin can lead to a rare but possible risk of something called lactic acidosis. This can happen when the kidneys aren’t able to clear metformin from the body, which leads to a buildup of lactic acid in the blood. Severe cases of lactic acid significantly alter the pH in the body, which can be life-threatening without treatment. But again, these cases are very rare — even in people with more advanced stages of kidney disease.

To know your risk of this side effect if you have kidney problems, it helps to know your stage of kidney disease. 

Kidney function is measured by something called the estimated glomerular filtration rate (eGFR). This is a laboratory estimate of how well your kidneys are filtering your blood. A lower eGFR means a more decreased kidney function. Experts recommend adjusting your metformin dosage based on this number. The result is measured in mL/min/1.73m². But you can just pay attention to the number itself: 

• eGFR 60 or higher: Safe for standard dosage with monitoring of kidney function every year

• eGFR 45 to 59: Safe for standard dosage with monitoring of kidney function every 3 to 6 months

• eGFR 30 to 44: Decreased dosage with monitoring of kidney function every 3 months

• eGFR below 30: Metformin shouldn’t be used (the medical term is “contraindicated”)

Currently, the guidelines recommend you not take metformin if your eGFR drops below 30 — or if you start dialysis. But it’s important to note that kidney specialists are starting to rethink and challenge this guideline. Even in people with an eGFR less than 30, research suggests that continued metformin treatment still leads to significant health benefits with a low risk of lactic acidosis. So, if you’re in this group, you should have a risks versus benefits discussion with your healthcare team to know if metformin is a good choice for you.

Does metformin help the kidneys?

Yes, metformin helps protect the kidneys from damage from diabetes.

Up to 40% of people living with Type 2 diabetes eventually develop kidney failure. One of the best ways to prevent this from happening is by keeping blood glucose in check. So, for people with diabetes, metformin plays an important role in keeping their kidneys healthy.

If you have CKD, there’s some evidence that: 

• Metformin may help slow the progression of kidney disease 

• Long-term use may lower the risk of kidney failure in people with advanced kidney disease

But other medications have stronger evidence for protecting the kidneys — such as sodium-glucose cotransporter-2 (SGLT2) inhibitors and glucagon-like peptide-1 (GLP-1) receptor agonists.

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Written by:

Julie Adkison, PharmD, BCACP, CDCES

Julie Adkison, PharmD, BCACP, CDCES, is a clinical pharmacist specializing in ambulatory care practice and diabetes care and education. She has worked in a faculty position in family medicine for many years.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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