Journal
JOURNAL OF CLINICAL ENDOCRINOLOGY & METABOLISM
Volume 101, Issue 4, Pages 1754-1761Publisher
ENDOCRINE SOC
DOI: 10.1210/jc.2015-3754
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Funding
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) of the National Institutes of Health
- NIDDK
- Intramural Research Program
- Indian Health Service
- National Institute of Child Health and Human Development
- National Institute on Aging
- Office of Research on Women's Health
- National Center for Minority Health and Human Disease
- Centers for Disease Control and Prevention
- American Diabetes Association
- Bristol-Myers Squibb
- Parke-Davis
- National Eye Institute
- National Heart, Lung, and Blood Institute
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Context: Vitamin B12 deficiency may occur with metformin treatment, but few studies have assessed risk with long-term use. Objective: To assess the risk of B12 deficiency with metformin use in the Diabetes Prevention Program (DPP)/DPP Outcomes Study (DPPOS). Design: Secondary analysis from the DPP/DPPOS. Participants were assigned to the placebo group (PLA) (n = 1082) or the metformin group (MET) (n = 1073) for 3.2 years; subjects in the metformin group received open-label metformin for an additional 9 years. Setting: Twenty-seven study centers in the United States. Patients: DPP eligibility criteria were: elevated fasting glucose, impaired glucose tolerance, and over-weight/obesity. The analytic population comprised participants with available stored samples. B12 levels were assessed at 5 years (n = 857, n = 858) and 13 years (n = 756, n = 764) in PLA and MET, respectively. Interventions: Metformin 850 mg twice daily vs placebo (DPP), and open-label metformin in the metformin group (DPPOS). Main Outcome Measures: B12 deficiency, anemia, and peripheral neuropathy. Results: Low B12 (<= 203 pg/mL) occurred more often in MET than PLA at 5 years (4.3 vs 2.3%; P = .02) but not at 13 years (7.4 vs5.4%; P = .12). Combined low and borderline-low B12(<= 298 pg/mL) was more common in MET at 5 years (19.1 vs 9.5%; P < .01) and 13 years (20.3 vs 15.6%; P = .02). Years of metformin use were associated with increased risk of B12 deficiency (odds ratio, B12 deficiency/year metformin use, 1.13; 95% confidence interval, 1.06-1.20). Anemia prevalence was higher in MET, but did not differ by B12 status. Neuropathy prevalence was higher in MET with low B12 levels. Conclusions: Long-term use of metformin in DPPOS was associated with biochemical B12 deficiency and anemia. Routine testing of vitamin B12 levels in metformin-treated patients should be considered.
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