It’s different for everyone. The rule of thumb that I’ve heard others mention is that Lupron (in my case Eligard) will remain in the body (and suppressing testosterone) for about as many more months as the injections were for. That actually happened in my case.

I had two 3-month injections, the 1st on 14 April 2021; the 2nd (& final) on 9 July 2021. My testosterone went as low as 3.0 ng/dL on 16 September 2021 (PSA down to < 0.008 ng/mL). My testosterone didn’t return to normal until my 25 February 2022 test - about 7 months after that 2nd (& final) 3-month injection.

My PSA started to slowly increase at that point, now varying between 0.3-0.5 ng/mL. At my most recent PSA test 3 weeks ago, my PSA was 0.43 ng/mL. Everything going as planned (so far).

Hope that helps answer your question.