It is natural in some persons to veins being popped out. Nature has arranged the systemeic supply of our blood circulation in such a way that all the arteries are deep seated within the soft tissues and veins places suprficially. So normally in lean persons veins do pop out which is not a symptom of disease.
Everybody's veins are different. some people have veins that show more than others. All that means is that they are closer to the surface. When I draw blood in the lab its easier to draw from someone who's veins are not so deep. His veins are normal. But you should try to convince him to lay off the drugs.
Usually its too much pressure like if your over weight or like in your legs if you run a lot and your putting all that strain on them...sometimes its also when your getting older and they can become weaker...hope this helps
On my mothly my vains pop on me all the time what do I do
Probably his veins are use to shooting up heroin. Usually they pop up when its warm/hot or when you rub them; hit them or tie(your hands) them up.