title: 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).
  
  
  CONCLUSIONS
  This study confirms the higher prevalence of vitamin B₁₂ deficiency in metformin-treated patients with type 2 diabetes than in those not treated with metformin. This study also suggests that vitamin D deficiency is not a clinical concern among metformin-treated patients with type 2 diabetes and that metformin does not negatively affect treatment of vitamin D deficiency in these patients.
authors.affiliation: Department of General Internal Medicine, Loyola University Medical Center, Maywood, Illinois 60153, USA. ekos@lumc.edu
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Kos
authors.forename: Mary Jo
authors.initials: MJ
authors.lastname: Liszek
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Emanuele
authors.forename: Ramon
authors.initials: R
authors.lastname: Durazo-Arvizu
authors.forename: Pauline
authors.initials: P
authors.lastname: Camacho
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001851:Bone Diseases, Metabolic / Q000139:chemically induced / Q000150:complications / Q000453:epidemiology; D002112:Calcifediol / Q000097:blood*; D015331:Cohort Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000150:complications / Q000188:drug therapy; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000009:adverse effects* / Q000627:therapeutic use; D007087:Illinois / Q000453:epidemiology; D008297:Male; D008499:Medical Records; D008687:Metformin / Q000009:adverse effects* / Q000627:therapeutic use; D008875:Middle Aged; D015995:Prevalence; D012189:Retrospective Studies; D014805:Vitamin B 12 / Q000097:blood*; D014806:Vitamin B 12 Deficiency / Q000139:chemically induced* / Q000150:complications / Q000453:epidemiology; D014808:Vitamin D Deficiency / Q000139:chemically induced / Q000150:complications / Q000453:epidemiology; D055815:Young Adult
chemical_list: D007004:Hypoglycemic Agents; D015652:25-Hydroxyvitamin D 2; D008687:Metformin; D014805:Vitamin B 12; D002112:Calcifediol