Hope someone can advise me ASAP plz! 5 days of taking 50mgs of levothyroxin but I have quite severe muscle pain that started yesterday it was my lower half, Calves burned like I'd run a marathon (I wish) today it's mainly the top half. My Vit D & Iron are very low and B 12 is boarder line 200. Is this a side effect that will subside or should I stop taking the Levothyroxine?. I also have Fibro & have had various Ops in the last 2 yrs due to hand pain (last 2 on spine!) Grrr I need this like a hole in the head lol. Many Thanks Sandra.