Table 1

Summary characteristics of included studies

First author, year (reference no.)CountryStudy populationNo. of patients% femaleMean age (years)Mean BMI (kg/m2)TreatmentControlDurationBaseline 25(OH)D for vitamin D/control groups (nmol/L)Achieved 25(OH)D for vitamin D/control groups (nmol/L)
Davidson, 2013 (25)U.S.Prediabetes and vitamin D deficient11767.952.432.5Vitamin D3 88,865 IU/weekPlacebo1 year52.5/52.5162.5/50.5
Dutta, 2014 (26)IndiaPrediabetes and vitamin D deficient17059.247.926.6Vitamin D3 60,000 IU/week for 8 weeks, then 60,000 IU/month + calcium 500 mg/dayCalcium 500 mg/day1 year42.5/4588.4/43.8
Barengolts, 2015 (27)U.S.Prediabetes, vitamin D deficiency, and overweight173059.031.9Vitamin D2 50,000 IU/weekPlacebo1 year36.7/35120/50
Kuchay, 2015 (28)IndiaPrediabetes147NA48.125.5Vitamin D3 60,000 IU/week for 4 weeks, then 60,000 IU/monthPlacebo1 year49.4/47.1108/55.9
Jorde, 2016 (29)NorwayPrediabetes51138.66230.0Vitamin D3 20,000 IU/weekPlacebo5 years59.9/61.1122.3/66.7
Kawahara, 2018 (16)JapanPrediabetes1,256NANANAEldecalcitol 0.75 μg/dayPlacebo3 yearsNANA
Niroomand, 2019 (30)IranPrediabetes16276.546.531.5Vitamin D3 50,000 IU/week for 3 months, then 50,000 IU/monthPlacebo6 months30.7/31.789.9/39.9
Pittas, 2019 (15)U.S.Prediabetes2,42344.86032.1Vitamin D3 4,000 IU/dayPlacebo5 years69.2/70.5135.8/72.0
  • Data are presented as mean unless otherwise indicated. To convert vitamin D IU to μg, multiply by 0.0025. NA, not available.