Levels of testosterone naturally decrease with age, but exactly what level constitutes "low T," or hypogonadism, is controversial, Harvard Medical School said. Testosterone levels vary wildly, and can even differ depending on the time of day they're measured (levels tend to be lower in the evenings). The National Institutes of Health includes the following as possible symptoms of low testosterone:
A blood test may not be enough to determine your levels, because testosterone levels can fluctuate during the day. Once you determine that you do have low levels, there are a number of options to take. There are synthetic and bioidentical testosterone products out on the market, but I advise using bioidentical hormones like DHEA. DHEA is a hormone secreted by your adrenal glands. This substance is the most abundant precursor hormone in the human body. It is crucial for the creation of vital hormones, including testosterone and other sex hormones.
Partake in short-term high-intensity exercise. Casual walking is great for weight loss, but high-intensity exercise (such as playing soccer, swimming or lifting weights) can directly stimulate testosterone production. However, the key is how long you spend doing the exercise as well as your intensity levels. Short bouts of high-intensity exercise (weightlifting in particular) has a proven positive effect on increasing testosterone levels and preventing its depletion in teenage and older males.[2] Thus, keep your workouts relatively short (no more than 30 minutes) and try to go full out in as safe a manner as possible. Working out for longer periods (an hour or more) at less intense levels can sometimes reduce testosterone levels in men / boys.

Every vitamin, mineral, and ingredient that affects the human body can be taken in enough quantities that they are harmful, or toxic, even the ones that — at lower levels — are beneficial or necessary. Unfortunately, testosterone boosters contain a lot of ingredients that are not well understood. This means in addition to not being able to confirm whether certain ingredients increase testosterone, the scientific and medical communities also don’t know at what levels many ingredients become toxic. On the up side, you might need to eat several pounds of a particular leafy plant before it becomes harmful. On the down side, it could be significantly less that pushes you over your body’s limit. We simply don’t know how little or how much the human body can tolerate. We recommend keeping your doctor in the loop when you add any supplement with unproven ingredients into your diet — they’ll be able to help you find and track any undesired side-effects that these ingredients might cause.

Overall, it seems that both estrogen and testosterone are important for normal bone growth and maintenance. Deficiency or failure of action of the sex hormones is associated with osteoporosis and minimal trauma fractures. Estrogen in males is produced via metabolism of testosterone by aromatase and it is therefore important that androgens used for the treatment of hypogonadism be amenable to the action of aromatase to yield maximal positive effects on bone. There is data showing that testosterone treatment increases bone mineral density in aging males but that these benefits are confined to hypogonadal men. The magnitude of this improvement is greater in the spine than in the hip and further studies are warranted to confirm or refute any differential effects of testosterone at these important sites. Improvements seen in randomized controlled trials to date may underestimate true positive effects due to relatively short duration and/or baseline characteristics of the patients involved. There is no data as yet to confirm that the improvement in bone density with testosterone treatment reduces fractures in men and this is an important area for future study.

Sharma, R., Oni, O. A., Gupta, K., Chen, G., Sharma, M., Dawn, B., … & Barua, R. S. (2015, August 6). Normalization of testosterone level is associated with reduced incidence of myocardial infarction. European Heart Journal, 36(40), 2706-2715. Retrieved from https://academic.oup.com/eurheartj/article/36/40/2706/2293361/Normalization-of-testosterone-level-is-associated