Kostic TS, Stojkov NJ, Bjelic MM, Mihajlovic AI, Janjic MM, Andric SA: Pharmacological doses of testosterone upregulated androgen receptor and 3-Beta-hydroxysteroid dehydrogenase/delta-5-delta-4 isomerase and impaired leydig cells steroidogenesis in adult rats. Toxicol Sci. 2011 Jun;121(2):397-407. doi: 10.1093/toxsci/kfr063. Epub 2011 Apr 6. [PubMed:21427060]
In non-human primates, it may be that testosterone in puberty stimulates sexual arousal, which allows the primate to increasingly seek out sexual experiences with females and thus creates a sexual preference for females.[39] Some research has also indicated that if testosterone is eliminated in an adult male human or other adult male primate's system, its sexual motivation decreases, but there is no corresponding decrease in ability to engage in sexual activity (mounting, ejaculating, etc.).[39]
As “the ultimate guide” I want this article to be the last resource you need when it comes to boosting your testosterone. I have spent years researching this stuff, and experimenting on myself. And in case I am incomplete, I have linked out at the bottom of this page to all the best resources for increasing testosterone around the web. I truly believe there is no better resource out there than what you’re reading right now.
There are a lot of test booster blends out there. A lot of them are junk. I have tried to cover the most effective herbs above. As always, I recommend doing your own research and experiment to see if you notice an effect. If you would like one easy herbal solution I recommend starting with Mike Mahlers Aggressive Strength product purely because I have solid anecdotal evidence of its effectiveness. But again, supplements should be seen purely as that - a supplement to a healthy diet, plenty of sleep, hard training with adequate rest.
Many endocrinologists are sounding the alarm about the damaging effects that come with exposure to common household chemicals. Called “endocrine disruptors,” these chemicals interfere with our body’s hormone system and cause problems like weight gain and learning disabilities. One type of endocrine disruptor is particularly bad news for our testosterone levels.
If in a 46 XY individual testosterone is either not produced in adequate concentrations as in gonadal dysgenesis (MacLaughlin and Donahue 2004), or in the absence of the enzyme 17 alpha-hydroxylase so that testosterone is not produced (Ergun-Longmire et al 2006), or testosterone androgen receptors are absent as in the androgen insensitivity syndrome (Hughes and Deeb 2006), phenotypic females will result.
Recently, a panel with cooperation from international andrology and urology societies, published specific recommendations with regard to the diagnosis of Late-onset Hypogonadism (Nieschlag et al 2005). These are summarized in the following text. It is advised that at least two serum testosterone measurements, taken before 11 am on different mornings, are necessary to confirm the diagnosis. The second sample should also include measurement of gonadotrophin and prolactin levels, which may indicate the need for further investigations for pituitary disease. Patients with serum total testosterone consistently below 8 nmol/l invariably demonstrate the clinical syndrome of hypogonadism and are likely to benefit from treatment. Patients with serum total testosterone in the range 8–12 nmol/l often have symptoms attributable to hypogonadism and it may be decided to offer either a clinical trial of testosterone treatment or to make further efforts to define serum bioavailable or free testosterone and then reconsider treatment. Patients with serum total testosterone persistently above 12 nmol/l do not have hypogonadism and symptoms are likely to be due to other disease states or ageing per se so testosterone treatment is not indicated.

Why the difference? The discrepancy in findings between these studies is likely due to the initial training status and base testosterone levels of the subjects. While more research is warranted on this ingredient, D-AA is one of several ingredients suggested to be effective in boosting test levels, especially for older men whose natural testosterone levels have declined due to the natural course of aging.

Caffeine. Use caffeine moderately. Too much of the jittery juice increases cortisol, which decreases testosterone. Moreover, consuming caffeine late in the day hurts sleep, which lowers testosterone production. But one recent study indicates that caffeine consumed before working out may boost testosterone levels and help you exercise more efficiently. During my experiment I popped a piece of caffeinated gum five minutes before my workouts. Each piece had 100 mg of caffeine, about the same amount in a cup of coffee. That was usually it for my caffeine intake that day.
It's important to understand that your body requires saturated fats from animal and vegetable sources (such as meat, dairy, certain oils, and tropical plants like coconut) for optimal functioning, and if you neglect this important food group in favor of sugar, grains and other starchy carbs, your health and weight are almost guaranteed to suffer. Examples of healthy fats you can eat more of to give your testosterone levels a boost include:

Before the ready availability of non-injectible testosterone preparations, and because of their ease of administration by the oral route, 17-alkylated steroids were popular surrogate agents for testosterone. These substances, however, were capable of inducing several risk factors for coronary artery disease (Kopera 1993; Hall and Hall 2005) and as a consequence, particularly after the revelations of extensive 17-alkylated anabolic steroid abuse by athletes, testosterone, became unjustly incriminated. The evidence, however, tends to suggest just the opposite; testosterone may even be cardioprotective. Dunajska and colleagues have demonstrated that when compared to controls, men with coronary artery disease tend to have: lower total testosterone levels and free androgen indices, more abdominal fat, higher blood sugar and insulin levels (Dunajska et al 2004).

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6. Foods rich in vitamin D. If you’ve been thinking of increasing your testosterone levels, you better stock up on those mushrooms, salmon and milk. Clinical Endocrinology’s August 2010 issue published a study that was conducted by Austria’s Medical University Graz. According to the researchers, mushroom, salmon and dairy products are examples of food that are rich in Vitamin D. These researchers also found a relationship between Vitamin D and testosterone. Their study has shown that individuals with high levels of Vitamin D also had high testosterone levels. The obvious inverse relationship was true as well.  Click here for a convincing study on HUMAN BEINGS to back this up.
Pellets. Your doctor will place the testosterone pellets under the skin of your upper hip or buttocks. Your doctor will give a shot of local anesthesia to numb your skin, then make a small cut and place the pellets inside the fatty tissues underneath your skin. This medication dissolves slowly and is released over about 3-6 months, depending on the number of pellets. 
In fact, high cortisol deals a crushing blow to testosterone in two ways. During, long-lasting stress, high amounts of cortisol release very often and have a direct negative influence on T levels. Thus, cortisol inhibits testosterone synthesis in the testes and hypothalamus. In addition, the production of cortisol is impossible without cholesterol. But testosterone synthesis also demands cholesterol. Since during stress cholesterol is first of all used for making cortisol, T levels simply plummet.
"The Journal of Clinical Endocrinology and Metabolism" published that males who switched from a high-fat diet to a low-fat diet also saw a decrease in their testosterone levels. If you want to put some fat back into your diet without fearing cardiac implications, plant-based saturated fat like coconut is just the ticket. Meat-based fat is also acceptable if kept to less than 10% of your dietary fat intake.
The steroid hormone known as dehydroepiandrosterone, DHEA, plays an important role in sexual behavior, mental health and muscle growth. Your body uses this hormone to make sex steroids. Thus, taking a DHEA supplement should increase your circulating testosterone. A 2018 paper in the International Journal of Sports Medicine explored this possibility in athletic women.
In males, testosterone is synthesized primarily in Leydig cells. The number of Leydig cells in turn is regulated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In addition, the amount of testosterone produced by existing Leydig cells is under the control of LH, which regulates the expression of 17β-hydroxysteroid dehydrogenase.[128]

Testosterone is included in the World Health Organization's list of essential medicines, which are the most important medications needed in a basic health system.[107] It is available as a generic medication.[10] The price depends on the form of testosterone used.[108] It can be administered as a cream or transdermal patch that is applied to the skin, by injection into a muscle, as a tablet that is placed in the cheek, or by ingestion.[10]

On the average, you need to sleep at least 8 hours per night to stay healthy. If you want a night sleep to contribute to the maximum testosterone production, it’s important to make your sleep comfortable. Thus, the bedroom temperature shouldn’t exceed 21°C. In addition, you should ventilate your bedroom thoroughly before sleeping. Furthermore, before going to bed, don’t overload your stomach with fatty foods, as well as don’t drink alcohol and caffeinated beverages. Finally, you have to avoid intense physical activity before bedtime.6

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Zinc is involved in virtually every aspect of male reproduction, including testosterone metabolism. Several studies support the use of zinc for treating low sperm counts, especially when accompanied by low testosterone levels. In these studies, zinc has shown an ability to raise both sperm counts and testosterone levels. Many men may be suffering from low testosterone simply because of a zinc deficiency. Taking 30–45 mg of zinc per day is recommended; balance with 2–3 mg of copper for best results.

The researchers found that the dose of testosterone required to produce different effects in the body varied widely. The influence of testosterone and estradiol also differed. As the testosterone gel dose was reduced, the scientists showed, reductions in lean mass, muscle size, and leg-press strength resulted from decreases in testosterone itself. In contrast, increases in body fat were due to the related declines in estradiol. Both testosterone and estradiol levels were associated with libido and erectile function.

Testosterone retains nitrogen and is an essential ingredient in the development and maintenance of muscle mass (Sinha-Hikim et al 2006). With a diminution in testosterone, muscle mass diminishes as does strength. Weakness and fatigue result. A number of studies have demonstrated the ability of testosterone to restore lean body mass (muscle) in hypogonadal men, while at the same time causing a reduction in fat mass (Wang et al 2004). Treatment of hypogonadal men with testosterone results in improvement in overall physical performance as well as strength as assessed by, eg, hand grip power (Page 2005). Because of decreased muscle strength and impaired balance, older hypogonadal men are susceptible to falling and since they may already be osteopenic or osteoporotic as a consequence of hypogonadism, they are at increased risk for fracture as a result of the fall (Szulc et al 2003). Men with low levels of testosterone as in androgen deprivation therapy for prostate cancer, have a significant decrease in lean body mass and hemoglobin, while at the same time they experience an increase in weight, body fat and body mass index (Smith et al 2002). Treatment of frail hypogonadal men with testosterone, therefore, can result in changes in muscle gene expression, increased muscle mass, improvements in strength, power and endurance and improved physical function.
One of the most important nutrients that can help boost testosterone levels is vitamin D3. In 2011, the results of a study published in the journal Hormone and Metabolic Research announced that vitamin D supplementation boosts testosterone naturally in overweight men by up to 30 percent. (12) This is pretty exciting because research has shown that vitamin D3 is also linked to helping to prevent and treat cancer! (13)
Autopsy studies have found histological prostate cancer to be very common, with one series showing a prevalence of greater than fifty percent in men over age sixty (Holund 1980). The majority of histological cancers go undetected so that the clinical incidence of the disease is much lower, but it is still the most prevalent non-skin cancer in men (Jemal et al 2003). Prostate cancer is also unusual in comparison to other adult cancers in that the majority of those with the disease will die of other causes. Treatment of prostate cancer with androgen deprivation is known to be successful and is widely practiced, indicating an important role for testosterone in modifying the behavior of prostate cancer. In view of this, testosterone treatment is absolutely contraindicated in any case of known or suspected prostate cancer. The question of whether testosterone treatment could cause new cases of prostate cancer, or more likely cause progression of undiagnosed histological prostate cancer that would otherwise have remained occult, is an important consideration when treating ageing males with testosterone.

Falling in love decreases men's testosterone levels while increasing women's testosterone levels. There has been speculation that these changes in testosterone result in the temporary reduction of differences in behavior between the sexes.[53] However, it is suggested that after the "honeymoon phase" ends—about four years into a relationship—this change in testosterone levels is no longer apparent.[53] Men who produce less testosterone are more likely to be in a relationship[54] or married,[55] and men who produce more testosterone are more likely to divorce;[55] however, causality cannot be determined in this correlation. Marriage or commitment could cause a decrease in testosterone levels.[56] Single men who have not had relationship experience have lower testosterone levels than single men with experience. It is suggested that these single men with prior experience are in a more competitive state than their non-experienced counterparts.[57] Married men who engage in bond-maintenance activities such as spending the day with their spouse/and or child have no different testosterone levels compared to times when they do not engage in such activities. Collectively, these results suggest that the presence of competitive activities rather than bond-maintenance activities are more relevant to changes in testosterone levels.[58]
In females, this test can find the reason you’re missing periods, not having periods, or having a hard time getting pregnant. Doctors can also use it to diagnose polycystic ovary syndrome (PCOS). That’s a hormone problem that can cause irregular periods and make it hard to get pregnant. A testosterone test can also reveal if you might have a tumor in your ovaries that affects how much of the hormone your body produces.
Lean beef, chicken, fish, and eggs are some of your options. Tofu, nuts, and seeds have protein, too. Try to get about 5 to 6 ounces per day, although the ideal amount for you depends on your age, sex, and how active you are. When you don't eat enough of these foods, your body makes more of a substance that binds with testosterone, leaving you with less T available to do its job.
Total levels of testosterone in the body are 264 to 916 ng/dL in men age 19 to 39 years,[165] while mean testosterone levels in adult men have been reported as 630 ng/dL.[166] Levels of testosterone in men decline with age.[165] In women, mean levels of total testosterone have been reported to be 32.6 ng/dL.[167][168] In women with hyperandrogenism, mean levels of total testosterone have been reported to be 62.1 ng/dL.[167][168]
Ashwagandha is sometimes included in testosterone supplements because of the hypothesis that it improves fertility. However, we couldn’t find sufficient evidence to support this claim (at best, one study found that ashwagandha might improve cardiorespiratory endurance). WebMD advocates caution when taking this herb, as it may interact with immunosuppressants, sedative medications, and thyroid hormone medications.
Stick to protocols that stress large degrees of muscle mass and are moderate- to high-intensity. Additionally, more seasoned gym-goers may want to incorporate forced repetitions periodically into their programs, as testosterone increases have been observed with this type of training.14 Incorporating other post-failure training techniques such as dropsets or partials may similarly be associated with higher T production.

There are several supplements on the market claiming to be natural testosterone boosters. I get these sorts of things in the mail all time. The companies that produce these products claim that the herbs (typically stinging nettle and tribulus) in their pills increase free testosterone by reducing SHBG. They also throw in some B vitamins for “increased energy and vitality.”

Epidemiological studies suggest that many significant clinical findings and important disease states are linked to low testosterone levels. These include osteoporosis (Campion and Maricic 2003), Alzheimer’s disease (Moffat et al 2004), frailty, obesity (Svartberg, von Muhlen, Sundsfjord et al 2004), diabetes (Barrett-Connor 1992), hypercholesterolemia (Haffner et al 1993; Van Pottelbergh et al 2003), hypertension (Phillips et al 1993), cardiac failure (Tappler and Katz 1979; Kontoleon et al 2003) and ischemic heart disease (Barrett-Connor and Khaw 1988). The extent to which testosterone deficiency is involved in the pathogenesis of these conditions, or to which testosterone supplementation could be useful in their treatment is an area of great interest with many unanswered questions.

Although some men believe that taking testosterone medications may help them feel younger and more vigorous as they age, few rigorous studies have examined testosterone therapy in men who have healthy testosterone levels. And some small studies have revealed mixed results. For example, in one study healthy men who took testosterone medications increased muscle mass but didn't gain strength.