Since its introduction in the United States 25 years ago, the drug metformin has become a mainstay of treatment for type 2 diabetes. While its exact mechanisms of action are still being figured out, it appears to prevent your liver from releasing too much glucose as well as make your body’s cells more sensitive to insulin.
Metformin is not a substitute for insulin, and it’s not widely prescribed along with insulin in people with type 1 diabetes. But a new study shows why doctors may want to consider prescribing it more to people with type 1 — not because it improves blood glucose control, but because of other benefits it can provide.
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Published in the Journal of Diabetes, the study looked at 731 adults with type 1 diabetes over a period of one year. A subset of 76 participants took metformin in addition to insulin for this duration, under the supervision of their doctor to make sure insulin doses could be adjusted as needed.
At the end of the year, HbA1c (a measure of long-term blood glucose control) had gone down in both the insulin-only and metformin groups. But only the metformin group was able to lower its insulin requirements at the same time, by an average of 0.02 units per kilogram of body weight per day — which translates to about 1.4 units per day for someone who weighs 150 pounds (68 kilograms). This may not sound like a lot, but taking metformin had the additional benefit of keeping body weight constant — while body weight increased by an average of about 2.9 pounds (1.3 kilograms) in the insulin-only group.
These results suggest that at least in people who are overweight or have abnormal blood lipid (cholesterol and triglyceride) levels, doctors should consider adding metformin to insulin as part of treating type 1 diabetes. Future studies may shine more light on who, exactly, within the type 1 population stands to benefit most from taking metformin.