Can You Take Metformin If You Have Kidney Problems?
Yes, but this will depend on how well your kidneys are working.
Metformin doesn’t damage your kidneys, but having kidney problems may raise your risk of serious side effects.
When your kidneys aren’t working at full capacity, metformin can build up in your body instead of being cleared out. While rare, excess metformin can raise your risk for a dangerous condition called lactic acidosis.
Depending on your kidney function, you may need to take a lower metformin dosage. In some cases, metformin may not be recommended at all.
BEST ANSWERMetformin’s effect on the kidneys has been studied for more than 2 decades. Research supports this answer.
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One of the most popular Type 2 diabetes medications is metformin (Fortamet, Glumetza). It’s known for lowering hemoglobin A1C — your average blood glucose (sugar) over 3 months — alongside some other benefits.
But questions often come up about metformin and its effect on the kidneys. So, can you take metformin if you already have kidney problems? And will metformin hurt your kidneys if they are healthy?
Let’s clear up the confusion and go over what you should know about taking metformin safely.
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What is metformin?
Metformin is often prescribed as a first-choice oral medication for Type 2 diabetes. You may also see metformin prescribed for prediabetes or gestational diabetes, but these aren’t official FDA-approved uses. When you’re prescribed metformin, it’s usually expected to be taken long term.
Metformin works in a few ways to help you reach your blood glucose goals. The first is by lowering the amount of glucose made by the liver. Two other important effects include making your body more sensitive to insulin and lowering the amount of glucose you absorb into your body from your diet.
For convenience, metformin is available in several different combination pills with other diabetes medications. On its own, metformin is available as immediate-release (IR) and extended-release (ER) tablets and an oral solution.
You’ll typically take metformin once or twice a day. Larger dosages may be divided into three daily doses. The maximum dosage of metformin is usually 2,000 mg to 2,550 mg per day. But your dosage will likely be lower if you have kidney problems. More on that later.
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. But your kidneys must be working normally to effectively get rid of metformin.
Can you take metformin if you have kidney problems?
Yes, certain people with kidney problems can take metformin. Whether it’s safe for you will depend on how well your kidneys are working.
If you already have some form of kidney disease, metformin may not clear out of your body properly. A buildup of metformin can lead to high levels of lactic acid in your blood, also known as lactic acidosis. Lactic acidosis can be a life-threatening condition. So, your kidney function is watched closely when you take metformin.
Kidney health is sometimes measured by the glomerular filtration rate (GFR). This is a laboratory estimate of how well your kidneys are filtering your blood. A lower GFR typically means lesser kidney function. Whether metformin is safe for you to take can depend on your GFR. And experts recommend adjusting your metformin dosage based on this number, too.
Your healthcare provider will run a test to figure out your GFR before you start metformin and during treatment. If your GFR is less than 60, they may run this test more often. And if your GFR is between 30 and 44, they may lower your metformin dosage. But if you have certain risk factors, they may lower your dosage, even if your GFR is higher.
If your GFR drops below 30, or if you start dialysis, metforminshould not be used. Your healthcare team will keep an eye on this number and make changes as needed.
Does metformin help the kidneys?
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 your blood glucose in check. So if you’ve been prescribed metformin, it’ll play an important role in keeping your kidneys healthy.
If you have chronic kidney disease (CKD), metformin may help slow your kidney damage from getting worse. And long-term use has been shown to lower the risk of kidney failure in people with advanced CKD.
Does metformin affect other organs?
No. Metformin isn’t known to affect other organs. But there are some long-term side effects that you should be aware of. This includes low vitamin B12 levels, which can lead to anemia (low blood count) and worsened nerve damage.
Besides advanced kidney problems, some health conditions put you at higher risk of lactic acidosis. In this case, metformin may not be safe used alongside the presence of:
Certain liver problems
Heart failure
Active alcohol use
Medical tests using contrast dye
Certain medications that interact with metformin
Make sure your healthcare provider has your full medical history. It’s also important that you’re open and honest with them about how much alcohol you drink.
So, is metformin safe?
Yes, metformin is safe for most people. Most commonly, you may experience temporary stomach-related side effects when first starting treatment. This includes diarrhea, nausea, and vomiting. For many people, these improve within the first few weeks.
If you’re at risk for experiencing low blood glucose (hypoglycemia), metformin can be a safer treatment option. Because of how it works, hypoglycemia is less likely to happen with metformin compared to many other diabetes medications. But if you take metformin with other diabetes medications, this risk can go up.
While rare, lactic acidosis is possible. This risk is higher if you have a history of kidney problems. Your healthcare provider should watch your kidneys during treatment to make sure that metformin is still safe for you to take.
The bottom line
Metformin is often a first-choice treatment for Type 2 diabetes. It’s not known to be harmful to your kidneys or other organs. But if you have kidney problems, there’s a greater risk of a serious condition called lactic acidosis.
Your healthcare provider should watch your kidney function while you’re taking metformin. Depending on your GFR, you may need to take a lower dosage. And in some cases, you may need to stop taking metformin.
Why trust our experts?
References
Baerlocher, M. O., et al. (2013). Metformin and intravenous contrast. CMAJ: Canadian Medical Association Journal.
Bryant Ranch Prepack (2022). Metformin hydrochloride [package insert].
Charytan, D. M., et al. (2019). Metformin use and cardiovascular events in patients with type 2 diabetes and chronic kidney disease. Diabetes, Obesity & Metabolism.
ElSayed, N. A., et al. (2023). 9. Pharmacologic approaches to glycemic treatment: Standards of care in diabetes—2023. Diabetes Care.
Food and Drug Administration. (2017). FDA Drug Safety Communication: FDA revises warnings regarding use of the diabetes medicine metformin in certain patients with reduced kidney function.
Kidney Disease: Improving Global Outcomes (KDIGO) Diabetes Work Group. (2022). KDIGO 2022 clinical practice guideline for diabetes management in chronic kidney disease.
Kwon, S., et al. (2020). The long-term effects of metformin on patients with type 2 diabetic kidney disease. Diabetes Care.
National Kidney Foundation. (n.d.). Diabetes - a major risk factor for kidney disease.
National Kidney Foundation. (n.d.). Estimated glomerular filtration rate (eGFR).
Orloff, J., et al. (2021). Safety and effectiveness of metformin in patients with reduced renal function: A systematic review. Diabetes, Obesity & Metabolism.
Out, M., et al. (2018). Long-term treatment with metformin in type 2 diabetes and methylmalonic acid: Post hoc analysis of a randomized controlled 4.3 year trial. Journal of Diabetes and its Complications.
U.S. Food and Drug Administration. (2016). FDA revises warnings regarding use of the diabetes medicine metformin in certain patients with reduced kidney function.
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