According to the article, it was his own

Apparently back pain was an ongoing problem for the gentleman, and he’d come up with a rather innovative plan to treat it by introducing his own ejaculate intravenously and intramuscularly.

For the previous year and a half he’d been giving himself a monthly shot of his own self-made tonic. In the wake of his most recent bout of back pain, he had even upped his dose to several injections