Hot weather: causes your veins to dilate and expand, allowing your body to cool itself by boosting blood flow to the skin’s surface. This makes the veins more visible until your body temperature stabilizes.
Hormonal changes: Normal hormonal fluctuations, such as during puberty, can temporarily cause veins to look more visible.
When to visit a doctor.
While most large veins in your hands are innocuous, if they are accompanied by additional symptoms, you should consult a doctor. These may indicate an underlying concern, such as:
