WHICH SUPPLEMENTS HELP?
The best vasodilator is L-Arginine; taking 3- to 6 grams before a workout will produce a big muscle pump and bring more veins to the surface.
Another supp that helps is creatine monohydrate. Creatine will help your muscle uptake more fluid (which helps to improve your blood fluid levels in your veins). There is no magic formula to bringing out your veins. Get real lean, drink plenty of fluid, and train like a mad man. Concentrating on these three things will have your veins popping out of your skin.