I'm 18 years old. I run and play football a lot, I'd say my diet is pretty lean and healthy though I'm quite thin.
Recently I've noticed veins bulge all over my body. I have one on my right thigh which starts all the way from my thigh down to my calves. And some prominent ones on the other leg. I have a ton of them on my arms as well.
Another thing is that these veins aren't visible all the time. they usually pop up during certain parts of the day. I just feel worried that there's a serious underlying issue that I don't know about. I do sit and lie down a lot as well.
Are these varicose or reticular veins? Diabetes? High blood pressure? And any tips in relieving this issue would be much appreciated
You need to see your G.P. Varicose veins would be there all the time.
Actually that should have said "wouldn't" and not "would"
You cannot exactly be sure what it is. You should concern with some specialist to know its symptoms and disease. Taker care.
It's a normal thing, have you ever seen bodybuilder? they have visible veins all over the hand or around the neck. It happens only when your body has less fat and high workout same as you.
First of all, you are thin & having a healthy diet, also play football which needs full stamina.
according to me its okay normal thing, if it does not look like normal thing as I explain then you have to take doctor treatment. One of my friends has the same issue, he purchased Varicose veins removal cream that helped him. here is the ref link - https://goo.gl/R6a5bM 
hope this will help you.
Thanks