Visible veins on your arms are in most cases a completely natural and harmless phenomenon. They are most often caused by a combination of anatomical and lifestyle factors.

Common and harmless causes

Low body fat: The less subcutaneous fat you have, the closer to the surface of the skin the veins are located and the more pronounced they are.
Age: As you age, the skin loses both elastin and collagen and becomes thinner, which makes the veins much more visible.
Physical exertion and exercise: When you exercise or do heavy work, your blood pressure increases and your muscles tense. This pushes the veins closer to the surface and dilates them (called vasodilation).

Heat and weather: In a warm environment, the vascular system dilates to help the body cool down, which causes the veins to bulge.
Genetics: Skin thickness and vascular structure are often hereditary.
When to be concerned and see a doctor

Visible veins rarely signal a health problem. You should be concerned if the following accompanying symptoms appear:

Sudden or severe pain in the hand or forearm
Swelling of the entire arm, palm or fingers

Redness, increased skin temperature to the touch or hard nodules along the vein (may indicate inflammation of the veins – phlebitis)
Change in skin color or the formation of non-healing wounds
If you only have prominent veins without any accompanying pain or swelling, it is purely an aesthetic issue.