Being on testosterone 1 month after FUE surgery, will that effect the treatment?

It is best to ask your surgeon about post operative care as each doctor has their unique regimen.  

Testosterone can injure hair follicles that are prone to the effects of its byproduct.  Thus, if you are suffering from male pattern hair loss you can be doing harm to your hair. Taking Propecia may slow down the hair loss process.

Testosterone transforms into DHT which can injure hair follicles predisposed genetically. If you have anchogenic (male pattern hair loss) alopecia  you will likely lose hair by using testosterone. Propecia may lessen the harmful effect of testosterone.