Blood is rarely collected in the major United States sports drug testing programs. At the Olympics, blood
is collected, but not as often as urine. For example, at the 2004 Athens Olympics, the laboratory receive
2926 urine samples and 691 blood samples . Some federations, such as Union Cycliste Internationale
collect blood before races for health tests (not doping-control tests), and athletes with atypical values
deemed medically unsafe (eg, high hematocrit) are not allowed to compete .
Testing urine is better than testing blood for most prohibited substances (small molecules, molecular
weight less than ~800 atomic mass units). Urine collection is noninvasive and yields a large volume of
sample, with higher drug concentrations than in blood and with far fewer cells and proteins to complicate
And here is Q&A with Dr. Don catlin who heads anti doping research. This is another blood-urine debate that relates to EPO
Dr. Catlin does doping test for a living...