Bulging veins are usually normal and are often simply a physical trait related to how close the veins are to the skin. In some people, the veins are naturally more superficial, which makes bulging veins more noticeable.
Bulging veins also tend to be more visible when there is less fat under the skin or when muscle mass increases. For this reason, visible veins are more common in people who are lean or very muscular. They can also become more noticeable on hot days because blood vessels naturally widen.
However, bulging veins in the legs can sometimes be a sign of varicose veins. In these cases, the veins are enlarged, twisted, and usually bluish-purple, and they tend to develop in the legs over time. Varicose veins are more common in women, but men can have them too.
Varicose veins may also cause symptoms such as pain, heaviness, or tired legs. Some people may also notice swollen feet and ankles, especially later in the day.