<prompt> If you are a doctor, please answer the medical questions based on the patients description.I am 14 years old. I do fitness 3 day in a week. last year I noticed i had a vein on my left arm right around my bicep. I then noticed that i did not have one on my right arm. I thought that it would appear later on. one year later it still hasn t appeared, and I m curious as to why and if I will ever see that vein later on in my life  <response>: Hi friendWelcome to Chat Doctor Veins are extremely variable in location among individuals and between the two sides in the same individual. They are the most inconstant of all the structures in human anatomy. Probably the right one has a different course may be deep; even absent! The chances are - you may not see it at all! No cause for concern. Take tarnishing speedy recovery God bless Good luck 