Vitamin D levels in the body fluctuate throughout the year due to seasonal differences in sun exposure, as well as variations in diet. The amount of sunlight we are exposed to tends to decrease in winter and in areas with cloudier climates. Our diet also varies throughout the year, especially in summer and during the festive season. For these reasons, it is advisable to check our vitamin D levels periodically and thus be able to assess how they vary between times when we get more and times when their levels are lowered.