When i stand up everything turns black sometimes i feel my heart beats very fast i have pain in elbow and fingers of my hand i also have stomach problem i also have pain in lower part of neck area there is pain somewhere inside in my back and pain in shoulder and my underarm I have ask a doctor on practo before this and he said that i have to take vitamin d3 I also have taken a test named 25 hydroxy vitamin D test and i have 7 ng/ml level