title: A predictive equation to guide vitamin D replacement dose in patients.
abstract: BACKGROUND
  Vitamin D is essential for bone health and probably the health of most nonskeletal tissues. Vitamin D deficiency is widespread, and recommended doses are usually inadequate to maintain healthy levels. We conducted a retrospective observational study to determine whether the recommended doses of vitamin D are adequate to correct deficiency and maintain normal levels in a population seeking health care. We also sought to develop a predictive equation for replacement doses of vitamin D.
  
  
  METHODS
  We reviewed the response to vitamin D supplementation in 1327 patients and 3885 episodes of vitamin D replacement and attempted to discern factors affecting the response to vitamin D replacement by conducting multiple regression analyses.
  
  
  RESULTS
  For the whole population, average daily dose resulting in any increase in serum 25-hydroxyvitamin D level was 4707 IU/day; corresponding values for ambulatory and nursing home patients were 4229 and 6103 IU/day, respectively. Significant factors affecting the change in serum concentrations of 25-hydroxyvitamin D, in addition to the dose administered, are (1) starting serum concentration of 25-hydroxyvitamin D, (2) body mass index (BMI), (3) age, and (f) serum albumin concentration. The following equation predicts the dose of vitamin D needed (in international units per day) to affect a given change in serum concentrations of 25-hydroxyvitamin D: Dose = [(8.52 - Desired change in serum 25-hydroxyvitamin D level) + (0.074 × Age) - (0.20 × BMI) + (1.74 × Albumin concentration) - (0.62 × Starting serum 25-hydroxyvitamin D concentration)]/(-0.002). Analysis of the dose responses among 3 racial groups-white, black, and others-did not reveal clinically meaningful differences between the races. The main limitation of the study is its retrospective observational nature; however, that is also its strength in that we assessed the circumstances seen in usual health care setting.
  
  
  CONCLUSIONS
  The recommended daily allowance for vitamin D is grossly inadequate for correcting low serum concentrations of 25-hydroxyvitamin D in many adult patients. About 5000 IU vitamin D3/day is usually needed to correct deficiency, and the maintenance dose should be ≥2000 IU/day. The required dose may be calculated from the predictive equations specific for ambulatory and nursing home patients.
authors.affiliation: From the Department of Pathology, Truman Medical Center (GS), and the Office for Health Services & Public Health Outcomes Research, Department of Biomedical and Health Informatics (AJB), University of Missouri-Kansas City School of Medicine, Kansas City, MO; and Heritage Laboratories International Inc., Olathe, KS (GS). gurmukhsinghmdphd@yahoo.com.
authors.forename: Gurmukh
authors.initials: G
authors.lastname: Singh
authors.affiliation: From the Department of Pathology, Truman Medical Center (GS), and the Office for Health Services & Public Health Outcomes Research, Department of Biomedical and Health Informatics (AJB), University of Missouri-Kansas City School of Medicine, Kansas City, MO; and Heritage Laboratories International Inc., Olathe, KS (GS).
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Bonham
mesh_terms: D000465:Algorithms; D005260:Female; D006801:Humans; D007297:Inpatients; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D012189:Retrospective Studies; D014807:Vitamin D / Q000008:administration & dosage* / Q000031:analogs & derivatives / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000188:drug therapy*; D014815:Vitamins / Q000008:administration & dosage*
chemical_list: D014815:Vitamins; D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: Ambulatory Care; Community Medicine; Drug Dosage Calculations; Laboratories; Nursing Homes; Osteoporosis; Primary Health Care; Vitamin D