Metformin is the most widely prescribed and best-studied medication for prediabetes. In the landmark Diabetes Prevention Program trial, metformin reduced the risk of developing type 2 diabetes by 31% compared to a placebo over about three years. But here’s the important context: lifestyle changes alone, including modest weight loss and regular exercise, reduced that risk by 58%, nearly twice as much. So the “best medicine” depends on your full picture, including your weight, your A1C level, and how much traction you’re getting with diet and exercise on their own.
What Prediabetes Actually Means
Prediabetes is defined by an A1C between 5.7% and 6.4%. Your blood sugar is elevated above normal but hasn’t crossed the 6.5% threshold that marks type 2 diabetes. This isn’t just a warning label. At this stage, your body is already struggling to manage insulin effectively, and without intervention, many people progress to full diabetes within a few years. The good news is that prediabetes is highly reversible, and medication is one tool that can help.
Why Metformin Is the Go-To Option
Metformin works primarily by reducing the amount of sugar your liver releases into your bloodstream and by helping your cells respond better to insulin. It’s been studied in prediabetes more than any other drug, and the evidence is consistent: it slows progression to diabetes, it’s safe for long-term use, and it’s inexpensive. Generic metformin typically costs less than $100 for a month’s supply, often much less with insurance or discount programs.
A systematic review of multiple trials found that for every 7 to 14 people treated with metformin over three years, one case of diabetes was prevented. The most effective dose in trials was 850 mg taken twice daily, though lower doses (250 mg two or three times daily) also showed benefit. For people of South Asian descent, lower doses may work just as well while causing fewer side effects.
The main downside is digestive discomfort. Up to 25% of people taking metformin experience gastrointestinal side effects like nausea, diarrhea, or bloating, and roughly 5% can’t tolerate it at all. Starting at a low dose and increasing gradually helps. Extended-release formulations deliver the same glucose-lowering benefit with less gut irritation, and for many people the side effects fade within a few weeks as the body adjusts.
Lifestyle Changes Outperform Medication
The Diabetes Prevention Program compared metformin, intensive lifestyle changes, and a placebo in over 3,000 people with prediabetes. The lifestyle group was coached to lose 7% of their body weight through healthier eating and to get at least 150 minutes of moderate physical activity per week. That group cut their diabetes risk by 58%, compared to 31% for the metformin group.
To put the numbers another way: preventing one case of diabetes over three years required about 7 people in the lifestyle program versus about 14 people taking metformin. Lifestyle changes were roughly twice as efficient. This doesn’t mean medication is unnecessary. For people who find sustained weight loss and exercise difficult to maintain, or whose blood sugar is on the higher end of the prediabetic range, metformin provides a meaningful safety net. Many clinicians recommend both together.
GLP-1 Medications for Prediabetes
Newer injectable medications originally developed for type 2 diabetes and weight management are showing promise for prediabetes as well. These drugs, which include liraglutide and semaglutide, mimic a gut hormone that helps regulate blood sugar and appetite. A meta-analysis of randomized trials found that GLP-1 medications significantly reduced A1C, fasting blood sugar, body weight, waist circumference, triglycerides, and LDL cholesterol in people with prediabetes.
Weekly semaglutide at 2.4 mg was particularly effective, lowering A1C by about 0.32 percentage points more than placebo. That may sound modest, but in prediabetes, where the entire range spans less than one percentage point (5.7% to 6.4%), that shift can mean the difference between progressing toward diabetes and reverting to normal.
The catch is cost. GLP-1 medications can range from a few dollars to over $10,000 per month depending on insurance coverage, compared to under $100 for metformin. Insurance coverage for prediabetes specifically (as opposed to diagnosed diabetes or obesity) varies widely and can be difficult to secure.
Other Medications That Have Been Studied
Acarbose
Acarbose works differently from metformin. Instead of affecting insulin or liver function, it slows the digestion of carbohydrates in your gut, blunting the blood sugar spike after meals. The STOP-NIDDM trial found that acarbose reduced the incidence of type 2 diabetes by about 36% in people with prediabetes and significantly increased the chance of blood sugar reverting to normal. It doesn’t get absorbed into the bloodstream, which limits systemic side effects, but it’s notorious for causing gas, bloating, and diarrhea, especially early on. Those symptoms tend to improve over time.
Thiazolidinediones
Rosiglitazone, an insulin-sensitizing drug, showed a striking 60% reduction in diabetes incidence in the DREAM study. However, participants taking it had a significantly higher rate of heart failure, roughly seven times that of the placebo group. An earlier drug in the same class, troglitazone, was pulled from the market due to liver toxicity. These safety concerns, along with typical weight gain of 2 to 5 kg, mean this drug class is rarely recommended for prediabetes prevention despite its strong glucose-lowering numbers.
Berberine as a Natural Alternative
Berberine, a compound found in several plants and available as a supplement, has drawn attention for its blood sugar-lowering effects. In a small head-to-head trial of 36 adults with newly diagnosed type 2 diabetes, berberine (500 mg three times daily) performed comparably to metformin at the same dose over three months. Both groups saw similar drops in A1C, fasting blood sugar, and post-meal blood sugar. Berberine actually outperformed metformin on triglycerides and total cholesterol.
These results are intriguing but come with caveats. The trial was small and conducted in people with type 2 diabetes, not prediabetes specifically. Berberine is sold as a supplement, which means it isn’t regulated for purity or potency the way prescription drugs are. It can also interact with other medications. If you’re interested in trying berberine, it’s worth discussing with your doctor, particularly if you can’t tolerate metformin.
Who Benefits Most From Medication
Not everyone with prediabetes needs a prescription. Current guidelines generally favor medication for people with specific risk factors that make progression more likely. You’re a stronger candidate for metformin if your A1C is at the higher end of the prediabetic range (closer to 6.4%), if you have a BMI over 35, if you’re under 60, or if you have a history of gestational diabetes. For people with milder elevations and fewer risk factors, lifestyle changes alone are often enough.
The practical reality is that most people benefit from a combination approach. Metformin doesn’t replace the need for exercise and dietary changes, but it can provide additional protection while you work on building those habits, or serve as a backstop if weight loss plateaus. Prediabetes is not a permanent diagnosis. With the right combination of tools, many people bring their blood sugar back into the normal range and keep it there.