I don't think there's much you can do about them. I don't have that problem but my viens are really small. I had blood work done a couple of weeks ago and they had to dig to find the vien in my arms and I felt every movement of the needle. In your avatar, you look really skinny so maybe try to gain a little weight so the subcutaneous fat can kind of surround them and they won't be so noticeable. I would try searching googleto see what foods you can eat that will help with creating fat under the skin and not inside the abdomen.
