You might expect one quick blood draw to settle the matter. Here is what the sources say about confirming low testosterone, in beginner terms.
Two morning tests
The my.clevelandclinic.org page on TRT sets out the diagnosis step this way. Before starting TRT, your healthcare provider will make sure low testosterone is an accurate diagnosis. Its list of what to expect includes this line: Two morning testosterone tests (for diagnosis).
Read those two points together. The aim is a confirmed number, not a guess from symptoms alone.
Why it takes two tests and a morning draw
The source names two tests, and it names morning. Those details are the practical part for you. If a clinic asks you to come in early, or to repeat a test, that matches what my.clevelandclinic.org describes.
Your clinician decides what else to order.
What to read before you go
Cost-free homework helps. Healthline's overview of hormone replacement therapy for men and Medical News Today's piece on HRT for males give plain-language background. For a more careful view, there is a narrative review of testosterone replacement therapy in men aged 50 and above and a paper on age-related hypogonadism and the risks of testosterone therapy with uncertain benefits. The titles alone show that the literature carries both promise and caution.
Labs are a job for a clinician
Ordering, reading and acting on hormone labs is not a home project. Do not start any product based on how you feel this week. The diagnosis step exists so that treatment is not decided from a hunch.
Ask a licensed clinician
A simple opener works: "Which tests do I need, and when should I come in for the draw?" Anyone new to this around Hackettstown can ask that without any background. A licensed clinician can tell you what your own results mean.