"I didn't run up to my standard during this year's Boston marathon," he told German TV channel ARD.
"To get my power of endurance up, he (a doctor) told me they will take care of it. I asked if this is considered doping. He said: 'No problem. The substance stays only three to four days in your blood circulation and then it is impossible to prove.'
"I went with it, because everyone told me, I wasn't the only one - and none of the others got caught for doping.
"I know that a lot of medical substances are used, which are injected straight to the blood for the body to have more oxygen. And when you run, you run so smooth. You have more stamina.
"When the prize money comes in the doctors want a piece of your success," Kisorio added.
"There are some doctors who settle down in popular athlete areas where you can find the training camps. These men just open a pharmacy and claim they are just selling legal medication. Then they approach the athletes. It is the same all over the country.
"Athletics Kenya knows now what the situation is like. Maybe this is an ongoing problem that finally surfaces."