Effect of metformin therapy on vitamin D and vitamin B₁₂ levels in patients with type 2 diabetes mellitus
Abstract
OBJECTIVE: To determine the effect of metformin on 25-hydroxyvitamin D [25(OH)D] and vitamin B₁₂ levels in patients with type 2 diabetes mellitus.
METHODS: We performed a retrospective review of medical records of patients treated between 2003 and 2009 at Loyola University Medical Center, Maywood, Illinois, in both ambulatory primary care and endocrinology clinics. The study cohort consisted of 706 patients with type 2 diabetes mellitus who were 20 to 93 years old (mean age, 63 ± 13) and had a mean body mass index of 33.1 kg/m². Of these patients, 42% were treated with metformin, and 34% had been diagnosed with osteoporosis or osteopenia.
RESULTS: Patients taking metformin had statistically significant lower vitamin B₁₂ levels than those not receiving metformin (P<.0001; 95% confidence interval [CI] = -220 to -84 pg/mL). No statistically significant difference was found between users and nonusers of metformin in regard to 25(OH)D levels when adjusted for variables (P = .297; 95% CI for mean difference = -0.7 to 2.2 ng/mL). Metformin use did not adversely affect successful treatment of vitamin D deficiency in this patient population as a whole, nor did it affect the subgroup with osteoporosis (P = .956). The patients with osteoporosis had statistically significant lower baseline 25(OH)D levels in comparison with those without osteoporosis, when adjustments were made for all variables (P = .003; 95% CI = 0.7 to 3.5 ng/mL).
CONCLUSION: This study confirms the higher prevalence…
How strong is the evidence?
Evidence Hub reads this as a cohort study, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 706 participants or records.
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