Serum testosterone
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
More sensitive tests can not only measure the total amount of testosterone in the blood, but can also determine how much of that total amount is "free" or "bioavailable" testosterone.