You may already know that metformin is a popular medication for people with type 2 diabetes. What you might not be aware of is that a number of people with type 1 diabetes also take metformin to help with issues like insulin resistance, excess weight, and reducing heart disease risk.

In the U.S. and most other countries, metformin is only approved for use in people with type 2 diabetes (one exception to this is France, where it’s been approved for type 1 since 1996). But for years, some healthcare professionals have been prescribing the drug to certain individuals with type 1 “off-label,” meaning it hasn’t been approved for this condition.

In Scotland, for instance, about 15% of adults with type 1 have been prescribed metformin, according to 2016 data. The U.K.’s national diabetes care guidelines recommend that providers consider prescribing metformin off-label to people with type 1 diabetes who have a body mass index above 25 (or 23 and above for Asians and Asian American adults) and want to optimize their blood sugar levels while minimizing insulin use.

Why? Experts suggest that the benefits of metformin, such as increased insulin sensitivity and modest weight loss, also apply to people with type 1 struggling with these issues, said Dr. Amy Chang, an endocrinologist at Scripps Health.

How metformin may help type 1 diabetes

Experts are increasingly recognizing that medications initially intended for people with type 2 diabetes may also support some with type 1.

Chang has seen firsthand in her practice that many individuals with type 1 diabetes experience a wide variety of positive changes on metformin. Mainly, it helps to keep blood sugars in range using less insulin and lose excess body weight at the same time. In some cases, she’s also seen greater time in range and lower cholesterol.

“That’s where medications traditionally for type 2 diabetes can actually be helpful,” Chang said.

Jenna Brothers, a diabetes care and education specialist and endocrinology physician assistant at Duke Health, also prescribes metformin to people with type 1 diabetes who are facing insulin resistance and weight gain.

“Metformin provides them with extra help to make the insulin they’re taking work a little bit better,” Brothers explained. “In turn, that usually helps them lose a small amount of weight – maybe five to 10 pounds.”

All of the people Brothers has prescribed metformin for have noticed improvements in their blood sugars as well.

Brothers also prescribes a nighttime dose of metformin in cases where individuals have a difficult time managing overnight blood sugar surges (sometimes called the dawn phenomenon), caused by a glucose release from the liver.

What the research says

Experts we spoke to agreed that while they see many individuals who do well with metformin in the real world, scientific research is lacking. Metformin was originally studied in people with type 2 diabetes; there is much less data for use in those with type 1. However, a handful of smaller studies provide evidence of potential benefits for some people.

While results are mixed, one study review noted the following positive effects of metformin for people with type 1 diabetes:

• Reducing insulin needs (by 5-10 units per day)
• Lowering A1C (by 0.6-0.9%)
• Weight loss (from 3-13 pounds)
• Lowering total cholesterol (by 11-16 mg/dL)

Researchers concluded that overall, metformin was linked to lower insulin requirements, but not lower blood sugars.

The largest single study on the topic tracked 428 adults with type 1 diabetes (average age 56) who had an elevated risk for heart disease. Researchers gave half the participants metformin and the other half a placebo and followed them over three years. They found that metformin slightly lowered body weight, LDL cholesterol (“bad” cholesterol), and insulin use. However, the biggest takeaway was the potential heart health benefits. Metformin was found to reduce the progression of atherosclerosis, a build-up of plaque in the arteries that can lead to heart disease.

Whether we see more research on metformin for type 1 diabetes is unclear as conducting large, long-term studies that could provide more solid data is expensive, Chang explained. Since metformin is available in a generic form, which makes it less profitable, there is less incentive for drugmakers to invest in this kind of research, she added.