Vitamin D high excess supplementation raises serum 25-OH-vitamin D3 as well as serum and urine calcium concentrations. Mice were fed a diet containing low (<5 IU/kg food), standard (1500 IU/kg food) or high vitamin D concentrations (75 000 IU/kg food). (A) Serum 25-OH D3 concentrations were measured using liquid chromatography-tandem mass spectrometry 15 weeks after diet onset (representative plots of three independent experiments; data given as mean ± SEM; n = 13–15). Total calcium, total phosphate and total sodium in serum (B, D and E) and urine (F–H) were quantified on an ARCHITECT c16000 analyser 10 weeks after vitamin D diet onset (representative plots of two independent experiments; data given as mean ± SEM; n = 7–8). (C) Ionized calcium was measured on a blood gas analyser GEM Premier 4000 10 weeks after vitamin D diet onset (data given as mean ± SEM; n = 5).