Key takeaways:
Metformin is a diabetes medication that’s sometimes prescribed off-label for people with prediabetes who have a high risk of developing Type 2 diabetes.
Metformin works for prediabetes by lowering the amount of glucose (sugar) absorbed and made by the body. It also makes the body more sensitive to its natural insulin.
Metformin dosages for prediabetes depend on how you respond to the medication. Generally, you’d start with a lower dose and slowly raise it if needed.
Metformin can reverse prediabetes for some people. But lifestyle changes, like diet and exercise, are more effective at reversing the condition.
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It’s estimated that 115 million adults in the U.S. have prediabetes. According to the American Diabetes Association (ADA), prediabetes is when your blood sugar levels are higher than normal but not high enough to diagnose diabetes. Some experts consider it an early stage of Type 2 diabetes.
Treatment for prediabetes focuses on improving diet and nutrition, increasing exercise, and, if needed, managing excess weight. But sometimes, this may not be enough.
Medications — like metformin — can help prevent Type 2 diabetes in some people with prediabetes. Here’s how.
How does metformin work?
Metformin is an oral medication that helps to lower blood glucose. It does this is in a few ways:
It lowers the amount of glucose produced by your liver.
It lowers the amount of glucose absorbed from the food you eat in your intestines.
It helps your body use its natural insulin more effectively.
For those at high risk of developing Type 2 diabetes, metformin can be a great choice. The medication has been studied for several decades and is generally safe for many people to take. It has a very low risk of sudden hypoglycemia (low blood glucose) and requires minimal monitoring by both you and your prescriber.
It’s also an effective medication, with the most research to support its treatment of prediabetes in those under age 60. In fact, it’s the only medication the ADA currently recommends for prediabetes.
Do I need metformin for prediabetes?
For many people with prediabetes, a diabetes-friendly diet and exercise can help manage and even reverse it. The main aim of treatment is to prevent prediabetes developing into Type 2 diabetes. And for many — but not all — people with prediabetes, intensive “lifestyle” changes can lower the risk of developing Type 2 diabetes by as much as 58%.
For some people, though, diet and exercise changes help, but they aren’t enough to prevent the onset of Type 2 diabetes. This may be because they have:
Other medical conditions
A lifestyle that’s difficult to change
Weight that’s hard to shift
A genetic risk that’s just too strong
In these “high-risk” situations, healthcare professionals may prescribe metformin off-label to prevent Type 2 diabetes.
Risk factors for Type 2 diabetes
You may be considered “high risk” for Type 2 diabetes in these cases:
You have a body mass index (BMI) of 35 or more.
You're age 35 or older.
Type 2 diabetes runs in your family.
You have a history of gestational diabetes (diabetes during pregnancy).
You’re of African, American Indian, Asian, Hispanic/Latino, or Pacific Islander descent.
Metformin dosage for prediabetes
Because taking metformin for prediabetes is an off-label use of the medication, there are no standard doses provided by manufacturers. Your metformin dosage will be unique to you, depending on your response to the medication. Your prescriber will help you find the dose that’s right for you.
Generally speaking, people start with low doses of metformin to help limit side effects (more on those below). An example of a starting dose of metformin might be 850 mg once a day — which is then increased to twice a day after a few weeks.
Metformin is available in immediate-release (IR) and extended-release (ER) versions. Metformin IR is typically taken twice daily with meals. Metformin ER is usually taken once a day with or without food.
How long does metformin take to work for prediabetes?
Metformin begins working after only a few doses. Many people see significantly lower blood glucose levels within the first week. But it may take a month or two to achieve the full effect. Since prediabetes is an off-label use for metformin, your prescriber will closely monitor your response and adjust your dosage as needed.
What are the common side effects of metformin?
Many of metformin’s common side effects affect the gastrointestinal (GI) tract. These include:
Nausea
Gas
Vomiting
These side effects most often happen when first starting metformin. Many people find they get better or go away after a few weeks. Taking your doses with food can help lessen them.
Some people also find that metformin IR is more difficult to tolerate. Many healthcare professionals will recommend switching to metformin ER to see if that helps. Discuss this option with your prescriber if GI side effects aren’t improving after a few weeks of taking the same dose of metformin IR.
Some people and websites will claim that changing your fiber intake or adding probiotics to your diet will also help decrease diarrhea. But these methods haven’t been well studied and aren’t currently recommended by the ADA.
Will I be on metformin forever?
There’s no way to know ahead of time how long you’ll need to be on metformin. Some people may be able to lose weight and lower their hemoglobin A1C — your average blood glucose over the past 3 months — enough to no longer need it. But others may need to take metformin long term. Your prescriber will help you figure out if or when you should stop metformin.
The ADA doesn’t provide guidance on how long to continue metformin for prediabetes. Keep in mind that it takes a few months to begin seeing A1C changes after starting metformin. So you’ll likely be taking it for at least several months to see how it works for you.
Can metformin reverse prediabetes?
Yes, metformin can reverse prediabetes in some people, especially people with excess weight. But metformin works best when you’re able to make lifestyle changes — such as following a diabetes-healthy diet and exercising regularly.
Frequently asked questions
There’s not a set A1C where you’ll automatically be prescribed metformin. If your A1C is in the prediabetes range, between 5.7% and 6.4%, your healthcare team may discuss dietary changes and weight loss before starting a medication. If you’re at high risk for developing diabetes, they may consider metformin earlier. An A1C greater than 6.5% is in the diabetic range, when metformin is more likely to be prescribed.
Currently, there are no medications that are FDA approved for prediabetes. The first choice for treatment is usually lifestyle changes. These often involve:
Diet
Weight loss
Exercise
Stopping smoking
People who are at high risk for Type 2 diabetes may also consider off-label use of metformin or weight-loss medications such as glucagon-like peptide-1 (GLP-1) agonists, like Wegovy and Ozempic.
Metformin can cause weight loss, which is listed as a side effect. Many people consider weight loss as a benefit, since losing weight often improves diabetes and prediabetes. The amount of weight loss using metformin is typically less than with other medications like GLP-1 agonists though.
There’s not a set A1C where you’ll automatically be prescribed metformin. If your A1C is in the prediabetes range, between 5.7% and 6.4%, your healthcare team may discuss dietary changes and weight loss before starting a medication. If you’re at high risk for developing diabetes, they may consider metformin earlier. An A1C greater than 6.5% is in the diabetic range, when metformin is more likely to be prescribed.
Currently, there are no medications that are FDA approved for prediabetes. The first choice for treatment is usually lifestyle changes. These often involve:
Diet
Weight loss
Exercise
Stopping smoking
People who are at high risk for Type 2 diabetes may also consider off-label use of metformin or weight-loss medications such as glucagon-like peptide-1 (GLP-1) agonists, like Wegovy and Ozempic.
Metformin can cause weight loss, which is listed as a side effect. Many people consider weight loss as a benefit, since losing weight often improves diabetes and prediabetes. The amount of weight loss using metformin is typically less than with other medications like GLP-1 agonists though.
The bottom line
Metformin isn’t a first-choice treatment for prediabetes. But it may be prescribed off-label to people at high risk for developing Type 2 diabetes. It may also be an option if your prediabetes isn’t improving with diet and exercise changes alone.
Why trust our experts?
References
American Diabetes Association. (n.d.). What is the A1C test?
American Diabetes Association. (2023). Standards of care in diabetes – 2023 abridged for primary care providers. Clinical Diabetes.
Centers for Disease Control and Prevention. (2026). Prediabetes: Could it be you?
ElSayed, N. A., et al. (2023). Prevention or delay of type 2 diabetes and associated comorbidities: Standards of care in diabetes – 2023. Diabetes Care.
PD-Rx Pharmaceuticals, Inc. (2022). Metformin HCL [package insert].
