To clarify that poster is not my son but a similar story of treatment and recovery I found on the web.

Would testosterone levels show up on a routine full panel blood test done by a gp?

I dont think they normally test for it. You will have to ask for it specifically. Be firm and state you want it done.

I'm not sure the saliva tests are accurate from what Ive read online. ypu will need a blood test for it.