Vitamin D plays important roles in the regulation of certain minerals (calcium, phosphorus), in the maintenance of bone, in the regulation of blood sugar, blood pressure, inflammation and immune system responses.
The amount of sun exposure required to produce Vitamin D is small - about a quarter of the time it would take before experiencing a sunburn, although this will vary age, skin type, season, time of day, and so on. Your body will store the Vitamin D it makes in your fatty tissues and release it during periods when your sun exposure is not sufficient to meet your Vitamin D needs.
In spite of this, Vitamin D deficiency is relatively common, especially for Canadians, because of reduced hours of sunlight, use of sunscreens and other sun-avoidance tactics. Older adults are even more at risk of Vitamin D deficiency because they have fewer skin receptors that convert sunlight to vitamin D, may not get vitamin D in their diet or have trouble absorbing it, or may have difficulty activating it because of reduced kidney function.
Adults need up to 4,000 IU of Vitamin D per day; children need amounts that vary by age, ranging from 400 IU for newborns to up to 4,000 IU for pre-teens and adolescents. Because Vitamin D is stored in body fat, it is possible to experience toxicity symptoms and people with kidney disease, atherosclerosis, sarcoidosis, histoplasmosis, hyperparathyroidism, and lymphoma should not take Vitamin D supplements without medical supervision.
Vitamin D can provide benefit for fibromyalgia symptoms in the following ways:
- reduce/eliminate anxiety and depression 
- reduce widespread pain 
- improve painful menstruation in women with fibromyalgia 
- improve sleep quality 
- reduce cognitive impairment (brain fog, memory lapses) 
Vitamin D can interact with other substances and medications such as:
- aluminum antacids
- Atorvastatin (Lipitor)
- Calcipotriene (Dovonex)
- Cimetidine (Tagamet)
- Digoxin (Lanoxin)
- Diltiazem (Cardizem, Dilacor, Tiazac)
- Heparin , Low molecular weight heparins (LMWHs), Lovenox, dalteparin (Fragmin), and tinzaparin (Innohep)
- lovastatin (Mevacor), clarithromycin (Biaxin), cyclosporine (Neoral, Sandimmune), diltiazem (Cardizem), estrogens, indinavir (Crixivan), triazolam (Halcion)
- Verapamil (Calan, Covera, Isoptin, Verelan)
- Thiazide diuretics including chlorothiazide (Diuril), hydrochlorothiazide (HydroDIURIL, Esidrix), indapamide (Lozol), metolazone (Zaroxolyn), and chlorthalidone (Hygroton)
If you are on any of these medications, consult your health care provider before taking Vitamin D.
- Armstrong, D. J., et al. "Vitamin D deficiency is associated with anxiety and depression in fibromyalgia." Clinical rheumatology 26.4 (2007): 551-554.
- Zabihiyeganeh, Mozhdeh, et al. "Effect of vitamin D on widespread pain index of fibromyalgia patients." Razi Journal of Medical Sciences 21.124 (2014): 106-112.
- Lasco, Antonino, Antonino Catalano, and Salvatore Benvenga. "Improvement of primary dysmenorrhea caused by a single oral dose of vitamin D: results of a randomized, double-blind, placebo-controlled study." Archives of internal medicine 172.4 (2012): 366-367.
- McCarty, David E., et al. "The link between vitamin D metabolism and sleep medicine." Sleep medicine reviews (2013).
- Nimitphong, Hataikarn, and Michael F. Holick. "Vitamin D, neurocognitive functioning and immunocompetence." Current Opinion in Clinical Nutrition & Metabolic Care 14.1 (2011): 7-14.