There are no studies showing its effects on healthy males, but it has been shown to drastically improve testosterone in infertile males (ref 77). It's also packed full of minerals, so is a great superfood nevertheless. I use the Sunfoods brand. Make sure you buy from a quality brand, as there are a lot of poor shilajit products out there, also some have been shown to be high in heavy metals. 
Zinc is little more of a nice-to-have ingredient than a must-have. It’s on our radar as an ingredient that possibly boosts testosterone levels, and while we couldn’t find enough supporting evidence that taking zinc would increase natural testosterone, low zinc levels have been connected to infertility. A low zinc level is also possibly a sign of hypogonadism. The closest support we found is in a study which found that people recovered from nutritional deficiency-related problems more quickly if they took a zinc supplement than those who did not. Zinc is available in many foods, such as oysters, fortified breakfast cereals, and red meat.
Dr. Anthony’s Notes: Vitamin D has about 100 other beneficial body functions outside of it's impact on testosterone. Make sure you take the active Vitamin D3 (not D2 – from plant sources!) It’s also advisable to get 20 minutes of sunshine daily (weather permitting) – without sunscreen. Verdict: this is one of the natural testosterone supplements that work. Best Food Sources of Vitamin D3: Wild Alaskan Salmon (#1), Sardines, Eggs How To Take Vitamin D3: Using 3000-5000IU of Vitamin D3 per day is a good safe, research supported dose. Your physician can also test your blood for D3 levels for more precise monitoring.

Garlic contains a compound that reduces the levels of cortisol, a type of stress hormone. This compound is known as allicin. Testosterone and cortisol vie for the same sites within muscle cells. When you get rid of the cortisol, you make sure that the testosterone can get working and keep yourself stress-free too. Experts claim that uncooked garlic is the best in this case as it is the most potent, so add it to your diet starting today.

Regardless of the method of testosterone treatment chosen, patients will require regular monitoring during the first year of treatment in order to monitor clinical response to testosterone, testosterone levels and adverse effects, including prostate cancer (see Table 2). It is recommended that patients should be reviewed at least every three months during this time. Once treatment has been established, less frequent review is appropriate but the care of the patient should be the responsibility of an appropriately trained specialist with sufficient experience of managing patients treated with testosterone.

Popular through the centuries in Ayurvedic healing (a traditional practice of medicine in India) ashwagandha is what is known as an "adaptogen." This means the body may be able to use it to help adapt to stressors. While many people supplement with it for reducing cortisol, anxiety, and fatigue levels, ashwagandha also holds relevance for us here with potential testosterone boosting benefits.[8]

It is a natural hormone present in the body known as Dehydroepiandrosterone (DHEA). It reduces the estrogen levels while boosting testosterone levels. It has been in use since so long to raise testosterone levels. Among all supplements, it is one of the famous and many researchers are working on it to tell how it stimulates testosterone production. It is banned for athletes and professional players.
"By expanding the boundaries of this disease to common symptoms in aging males, such as fatigue and reduced libido, drug companies seek to increase their markets and boost their sales," wrote Barbara Mintzes, an assistant professor at the University of British Columbia School of Public Health, and Agnes Vitry, a senior research fellow at the University of South Australia, in a 2012 article in the Medical Journal of Australia .
There is a negative correlation of testosterone levels with plasminogen activator inhibitor-1 (PAI-1) (Glueck et al 1993; Phillips 1993), which is a major prothrombotic factor and known to be associated with progression of atherosclerosis, as well as other prothrombotic factors fibrinogen, α2-antiplasmin and factor VII (Bonithon-Kopp et al 1988; Glueck et al 1993; Phillips 1993; De Pergola et al 1997). There is a positive correlation with tissue plasminogen activator (tPA) which is one of the major fibrinolytic agents (Glueck et al 1993). Interventional trials have shown a neutral effect of physiological testosterone replacement on the major clotting factors (Smith et al 2005) but supraphysiological androgen administration can produce a temporary mild pro-coagulant effect (Anderson et al 1995).

With the decline of ovarian function in menopause, not only do estrogen levels decline, but so does testosterone availability, since the ovaries contribute, either by direct secretion or through precursor production, about 50 percent of circulating testosterone. The other 50 percent is supplied by the adrenal glands. Many post-menopausal or oophorectomized women are symptomatic as a consequence of reduced testosterone, the leading symptom being loss of libido (Sherwin and Gelfand 1987; Simon et al 2005). There is an increasing trend toward testosterone supplementation in these women. Such supplementation may also lead, not only to increased libido, but to increased bone mineral density and an improvement in general overall sense of well-being including energy, strength, motivation and mood (Davis et al 1995; Davis et al 2000).
Like other supplements and medication, testosterone therapy comes with risks and possible side effects. This is particularly true if you try to take it for normal aging rather than for treatment of a condition. Also, the Cleveland Clinic points out that the effects that these supplements may have on your heart and prostate can lead to a number of potential issues. Complications include:
Some of these signs and symptoms can be caused by various underlying factors, including medication side effects, obstructive sleep apnea, thyroid problems, diabetes and depression. It's also possible that these conditions may be the cause of low testosterone levels, and treatment of these problems may cause testosterone levels to rise. A blood test is the only way to diagnose a low testosterone level.