I am 37 years old and live in the uk. I have been suffering with terrible fatigue on and off for 3.5 years now. Due to illness I do not get out much in the sun. The past 4 months the fatigue has been terrible and non stop. Recently my wrists and knees are hurting me too. The GP has checked my bloodwork many times over the past 3 years and the only thing they have found is that sometimes my thyroid is a little low but they say not low enough to warrant medication. The most recent blood test they gave me said my thyroid levels were ok. I have just had the results of a private blood test for full thyroid and vitamins as I am getting nowhere with the NHS here. The private blood test shows my Reverse t3 ratio is a little low and my vitamin D levels are 55.6nmol/l (22.4ng/ml I believe?). I have been taking 5000iu Vitamin D the past few days but today I have doubled the dose to 10000iu. I will take 10000iu for 8 weeks and if my symptoms of fatigue and joint aches improve I will reduce dosage to 5000iu a day. Am I doing the right thing? I have found this website very good, great information, clear easy to navigate. Many thanks in advance.