Fig. 1
From: 25-Hydroxyvitamin D variability within-person due to diurnal rhythm and illness: a case report
Repeated pattern of daily fluctuation in blood-spot 25-hydroxyvitamin D levels. Each dot represents the mean measurement of five separately sampled blood-spot 25-hydroxyvitamin D test samples taken from one person. At days 1 and 2, the midday samples were taken 1 hour after the preceding daily, 5000 IU dose. At days 3 and 4, the midday samples were theoretical trough values, that is, sample was taken approximately 24 hours after the preceding daily, 5000 IU dose. 25(OH)D 25-hydroxyvitamin D