If you actually have low testosterone, many doctors will prescribe supplements. It may take some work to find one who doesn't consider age-related decline to be "normal", and so not warranting treatment. And if you can't, then you'll need to shop online.
They are a content farm owned by Internet Brands and their only focus is creating content as vehicles for pharmaceutical and consumer packaged goods advertisements.
But there's a problem, if your testosterone level is too low. In my experience, that increases the risk of tendonitis. Also, it didn't seem that exercise did much good. At least, not for strength training.
But with testosterone supplementation, exercising builds muscle and reduces fat. And no tendonitis. Also better blood sugar management, and less acne. Maybe even darker hair. But clearly not more hair on my head.