Yep they just draw blood. Two things to keep in mind. Some people are successful with spiro even if their testosterone ISN'T elevated, because some people are more prone to testosterone's negative effects. But with your other symptoms there is definitely a chance yours is elevated.
The other thing I've experienced is unless your acne is bad, an endocrinologist is less likely to understand your concern than a dermatologist. Mine puts in his notes all the time "patient has no acne" and I want to scream that I am on 4 meds to control it! (Spiro, Differin, Rosac, and Desogen). My dermatologist sent a note to my endocrinologist to prescribe spiro for me if possible and that was a huge help.
I'm on 100mg a day and was doing really well (along with my other treatments) until very recently. I suspect my hormones have gotten much worse and will definitely be asking my endo to increase the dose if possible.
And nobody asked about this but since people on spiro will be reading this I thought I'd volunteer this info :) This month, without asking beforehand what the price would be, I ordered name brand spiro. I felt like I was getting an uneven dose on generic. The good news: I am actually sleeping through the night and not having to get up and pee 5 times. The bad news: It costs $70.
So I'm going back to generic next month :(