I've just been reading a book on vitamin d and it states that an astonishing majority of us who do not supplement adequately with D3 or sunbathe regularly are deficient in vitamin D. The new optimal level is 60 nmol or above. I had my levels tested last summer and it was very low (11), my brother's who regularly gets outside wasn't even registrable.
Anyway, it was stated in this book that low levels of vitamin D can be the cause of pain, including fibromyalgia. So it would be a really idea to get those levels tested and if you are low then supplement with AT least 5,000iu at minimum. I took 20,000iu daily to get my levels up from 11 to 64 in 3 months.
Get it tested now before the flu season starts, stock up on D3 to have on hand in case the flu hits. It's recommended that you take 1,000iu per pound of body weight for 3-5 days, at the onset of cold or flu. BioTec has D3 in 1,000, 5,000 and 50,000iu