It is going to depend on where you live and who you see about it, as well as what your symptoms are. As noted above, a specialty TRT clinic will almost definitely prescribe for you. The 1st guy I went to - I'm 45, btw, and been on TRT for roughly 2 years) - told me when reviewing my initial bloodwork (my T level was 395) that everyone under 600 gets treated. Provided you're symptomatic. Keep in mind, those places are in business to sell TRT. many, if not most, don't accept insurance, they want cash customers.
Some of those places are not run by doctors - which doesn't really matter to me, as I've found that most doctors have their heads so far up their asses regarding hormones (or at least testosterone) it isn't even funny. I've gotten more reliable and accurate info on the subject here, from knowledgeable members. The clinic I went to when I lived in Vegas was run by a PA; the one my buddy goes to has a physician "on staff": the doc is the owner's father and is available, but not there all the time. The owner is just a guy who owns a business, to be a TRT clinic. All of the foregoing is purely information. It is not intended as a criticism or anything else. Like I said, every doctor except one that I've spoken to about TRT and my symptoms has had his head totally up his or her ass. So as far as I'm concerned, a clinic is a very viable option, especially if they'll take your insurance, and if your insurance will pay.
I have since moved from that area and over the past year and several months have been trying to find a doc to competently deal with this issue . I seem to have found one. Be aware, though, that he told me that some medical body (CDC maybe? I forget, maybe there's some other medical society...) recently issued a position statement declaring rhat "normal, age related" low testosterone does NOT indicate treatment, and therefore "we are off the reservation with this." So far he's still ok prescribing it, however.
What I suggest is that you read up on it as much as possible here, ask questions, and "interview" some doctors until you find one who knows what he is talking about. This is a royal PITA, it is time consuming and frustrating. If you're lucky, you'll find one who knows his shit and is willing to help you. If not, after you've done your homework, if you look around here enough, you'll figure out where to get what you need along with any supporting compounds - such as HCG, AI's, etc, along with PCT if you try it and decide to stop.
So, what I'm trying to tell you is that you do have options. But you MUST do your homework; be very well informed; and be your own advocate.
O, and if a doctor tells you that testosterone has nothing to do with erections, consider that interview over, and that particular doctor as having failed the interview. I've heard this statement from a GP, a urologist, and an endocrinologist as well as a PA and a nurse. ED is what led me to TRT in the first place, and when my test level is in the right range, I get wood like a teenager. Too low, it's a dangling disappointment. Too high, it's also a dangling disappointment.
I hope this long winded post is helpful. It's based entirely on my own experience. Which includes getting a lot of solid info on this forum right here.