My mother has been complaining of a constant, mild pain in her upper left arm, just above the elbow and below the shoulder. Its not severe, but it bothers her when shes trying to fall asleep. A few months ago, she had pain in her elbow, but that seems to have improved. She thinks the pain might be related to the way she sleeps, since she tends to sleep with her arms beneath her body instead of on her side, but she cant change this sleeping position. Shes otherwise healthy with normal blood pressure, and her last diagnostic tests for sugar and other parameters were in October 2015. Her Vitamin B12 and D3 levels were low, but she finished the prescribed supplements and isnt taking any medication now. Do you have any advice on this pain or what could be causing it?

I would advice to undergo Vitamin D3 tests and Vitamin b12 again to know the values now.