Adequacy of vitamin D replacement in severe deficiency is dependent on body mass index

Am J Med. 2009 Nov;122(11):1056-60. doi: 10.1016/j.amjmed.2009.06.008.


Background: Obesity is associated with hypovitaminosis D. Whether body mass index (BMI) determines the replacement dose of vitamin D to achieve sufficiency is unclear.

Objective: To determine the relationship between BMI and serum 25-OH vitamin D concentrations and whether the increase in serum 25-OH vitamin D concentrations with vitamin D replacement is dependent on BMI.

Methods: Retrospective review of anthropometric data and serum 25-OH vitamin D concentrations in 95 patients attending an outpatient clinic in a tertiary hospital. In a second component of the study, 17 hospital inpatients with severe vitamin D deficiency (serum 25-OH D concentrations<6 ng/mL [15 nmol/L]) were supplemented with 10,000 units vitamin D(3)/day orally for 1 week. Biochemistry and anthropometric measurements were compared before and after vitamin D replacement.

Results: Serum 25-OH vitamin D concentrations correlated negatively with BMI in the 95 outpatients (r(2) = 0.11, P <.01). In the longitudinal study, BMI correlated positively with serum intact parathyroid hormone (r(2) = 0.84, P <.01) and negatively with 1.25-(OH)(2) vitamin D (r(2) = 0.19, P=.06) at baseline. Serum 25-OH D concentrations achieved following 1 week of vitamin D(3) replacement correlated negatively with BMI (r(2) = 0.63, P <.01).

Conclusion: Efficacy of vitamin D supplementation is dependent on BMI. Overweight and obese patients with hypovitaminosis D might require higher doses of vitamin D to achieve vitamin D repletion compared with individuals with normal body weight.

Publication types

  • Comparative Study

MeSH terms

  • Aged
  • Aged, 80 and over
  • Body Mass Index*
  • Dose-Response Relationship, Drug
  • Female
  • Follow-Up Studies
  • Humans
  • Male
  • Middle Aged
  • Obesity / complications
  • Obesity / metabolism
  • Radioimmunoassay
  • Retrospective Studies
  • Severity of Illness Index
  • Surveys and Questionnaires
  • Treatment Outcome
  • Vitamin D / administration & dosage*
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / drug therapy*
  • Vitamin D Deficiency / etiology
  • Vitamins / administration & dosage*


  • Vitamins
  • Vitamin D