It's Vitamin D supplementation season in the Northern Hemisphere. EVERYONE* who lives here should be taking Vitamin D supplements between the Autumnal Equinox and the Vernal Equinox.
This very funny lecture by a very respected doctor will show you why. You may not understand ALL of the scientific jargon, but the layperson will still love this lecture.
Vitamin D deficiency is worldwide and an epidemic right now. The problem with that is that Vit D has a role in the proper function of every cell in the body. If you have a medical condition, ANY CHRONIC medical condition,* lack of enough Vit D in your body COUDL BE THE CAUSE!!!
Before masking your symptoms with a drug, try supplementing with cheap old vitamin D and see what happens*.
*there are a few (absolute and relative) contraindications to vitamin D supplementation, such as a history of renal stones, sarcoidosis, oat cell carcinoma of the lung, and non-Hodgkin's lymphoma, primary hyperparathyroidism, hypercalcemia, malabsorption syndrome, tuberculosis, and those who use cardiac glycosides (digoxin), thiazide diuretics or antithyroid medications.
So, please, ask you PCP about taking it first if you have ANY doubts.