Estimation of Vitamin D in Blood Serum

In a previous communication a method for the estimation of vitamin D in blood serum was described.1It was shown that the level of vitamin D in the serum of animals can be raised by a single administration of a large dose of viosterol and that the surplus of vitamin D disappears from the serum within a few weeks. In addition, the results of a number of estimations in serums of children and adults were reported. In the present study we wish to supplement the data concerning the level of vitamin D in human serums. It seems desirable to know not only the average value of the vitamin D in human serums but the variations which may be expected. Since those variations, which may be due to physiologic fluctuations or to the limitations of the method, are rather large, a knowledge of the fluctuations observed in the blood of