What makes your veins darker than usual ?

Clots or dehydration: If you are dehydrated that may affect it slightly. If only a small area of a vein is darker than usual it could have a small clot in it. If the area is also reddish (the surrounding skin) and painful it is a condition called thrombophlebitis. Use Motrin and heat to the area.

Normal.: The prominence of veins through the skin is affected by many factors including levels of hydration and dehydration, body temperature as well as outside temperature, medications and even levels of stress. Fair skinned people tend to have more easily visible veins than darker individuals and hereditary plays a strong role also. In a healthy person, visible veins are usually not of any concern.