A person like me is really skinny and underweight..fat in my body is less and veins appear easily...how frequently skinny people can have blood test if required? Does the vein become damaged once blood is drawn and same vein can't be used? Or same vein can be used over and over again. What happens to site where needle makes to puncture to draw blood. What if a person requires testing every month on account of a condition on chronic basis( long term), how frequently blood can be drawn safely. Please guide me with medical knowledge, and also if to change arm for drawing blood each time.