25-hydroxy-vitamin D levels in a patient with hypervitaminosis D.

We measured the concentrations of serum calcium and 25-hydroxy-vitamin D in a patient with hypervitaminosis D during 3 months of therapy directed toward correcting the hypercalcemia. Serum calcium could not be maintained at normal concentration without specific therapy until 9 weeks after vitamin D was discontinued. Concentration of 25-hydroxy-vitamin D at the time was 285 ng/ml, approximately half of the value measured three weeks after withdrawal of vitamin D. Serial measurements of the concentration of 25-hydroxy-vitamin D seem to be a useful means of assessing the degree of intoxication in patients with hypervitaminosis D.