What could cause blue veins on my abdomen and legs to be suddenly visible? i've had 2 negative pregnancy tests and have never missed a bc pill

Not concerning.: The prominence of veins through the skin is affected by many factors including levels of hydration, hormones, 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.