American Diabetes Association's 73rd Scientific Sessions:

DPPOS Confirms B12 Deficiency Risk from Long-Term Metformin Rx

Physicians need to be aware of the real risk of vitamin B12 deficiency in their patients who are on long-term metformin therapy, and screen for it, according to data from the Diabetes Prevention Program Outcome Study (DPPOS).

The DPPOS is the ongoing observational study of participants in the Diabetes Prevention Program (DPP), which compares the effects of lifestyle changes, metformin therapy, and placebo on the development of diabetes in those at risk for the disease.

Long-Term Risk Seen

After analyzing the data, the DPPOS team found that B12 levels and the prevalence of anemia did not differ by age in the first year of the DPPOS for either the metformin or placebo group, or in the ninth year for participants in the metformin group. However, over the 13 years of follow-up, 7.4% of participants in the metformin group developed vitamin B12 deficiency, compared to only 5.3% in the placebo group. The prevalence of the deficiency increased in the metformin group the longer the patients took the drug.

“We’ve had a unique opportunity in this study because of its length. With 13 years of follow-up, we can see the long-term effects of using metformin on vitamin B12,” Jill Crandall, MD, professor of clinical medicine at the Albert Einstein College of Medicine in N.Y. and poster co-author told EndocrineWeb in an interview.

“We’re not the first to report on this [phenomenon], but in practice, the risk is often not taken that seriously,” Dr. Crandall added. “Significant vitamin B12 deficiency can lead to permanent neurological damage even when anemia isn’t present. Our results are an important message for physicians and patients to be aware of this, and to consider periodic measurements using common, standardized lab tests.”

Need for Screening Seen

Dr. Crandall explained that a vitamin B12 deficiency would not necessarily require a discontinuation of metformin therapy. “That wasn’t addressed in the research, but by all other accounts, metformin is one of the best medications we have to treat diabetes. We’re not suggesting that patients be taken off metformin, just to be aware of the potential for a B12 deficiency and the need for physicians to screen for it.”

In the original DPP, overweight patients with prediabetes were randomized to three groups. The lifestyle intervention group received intensive training in diet, physical activity, and behavior modification, with the goals of eating less fat and fewer calories, exercising for a total of 150 minutes a week, and losing at least 7% of their body weight. The metformin group took 850 mg of the drug twice per day, whereas the third group took placebo. Eighty-eight percent of all surviving DPP participants who were eligible joined the DPPOS.


Dr. Crandall reported no conflicts of interest.

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