Correlation of seasonal variation of 25-hydroxycalciferol with UV radiation dose

Plasma 25-hydroxycalciferol levels were measured in ten normal subjects at approximately 6-weekly intervals for 1 year. The mean annual level was 18.4 ng/ml with a seasonal variation from 14 to 26 ng/ml. These values correlated well with serial estimates of personal UV radiation dose previously measured by polysulphone film badges.