"Some say it's just a part of aging, but that's a misconception," says Jason Hedges, MD, PhD, a urologist at Oregon Health and Science University in Portland. A gradual decline in testosterone can't explain a near-total lack of interest in sex, for example. And for Hedges' patients who are in their 20s, 30s, and early 40s and having erectile problems, other health problems may be a bigger issue than aging.
Now that we know chronic insulin spikes lead to lower Testosterone production, I hope I haven’t sent you running into the low carb camp! There are a few studies out there showing that long term low carb or ketogenic dieting leads to higher cortisol levels (especially with subjects who are training), and decreased testosterone levels (28 & 29). I have used low carb diets in the past with successful results (winning a national bodybuilding title), however the key is to use cyclical carb re-feeds. If you’re going to go on a low carb diet for whatever reason, be sure to work in a large carb reefed once a week.
Sprinting has been shown numerous times that it has positive effects on testosterone levels. One 2011 study (ref 84) looked at weightlifters who performed 4x35m sprints twice a week. In contrast to the control group (who continued lifting but did not sprint), it was found that “After the 4-week training program, total testosterone and the total testosterone/cortisol ratio increased significantly in the (sprinters) EXP group”.

Directions — SUGGESTED USE: As a dietary supplement take 3 capsules daily, preferably with a meal, or as directed by a healthcare professional. — Take two capsules with a meal twice a day. On days that you are not training, take two capsules in the morning and two capsules at night. On days that you train, take two capsules about an hour before workouts and take two capsules in the morning or at night depending on when you train.
Fenugreek is often found in Indian, Turkish, and Persian cuisine. Multiple studies have found it to improve testosterone levels, and in particular, sexual performance. Scientists at Babu Banarasi Das University and King George’s Medical University in India have found that fenugreek improved testosterone levels. Testosterone levels increased for 90% of the volunteers, sperm morphology (the size and shape of sperm) improved for 14.6%, and more than 50% of volunteers experienced improvements in mental alertness, mood, and libido.
In fact, testosterone supplements might cause more problems than they solve. Studies have suggested a connection between supplements and heart problems. A 2010 study reported in The New England Journal of Medicine showed that some men over age 65 had an increase in heart problems when they used testosterone gel. A later of men younger than 65 at risk for heart problems and heart-healthy older men showed that both groups had a greater risk of heart attack when taking testosterone supplements.

Testosterone is a steroid from the androstane class containing a keto and hydroxyl groups at the three and seventeen positions respectively. It is biosynthesized in several steps from cholesterol and is converted in the liver to inactive metabolites.[5] It exerts its action through binding to and activation of the androgen receptor.[5] In humans and most other vertebrates, testosterone is secreted primarily by the testicles of males and, to a lesser extent, the ovaries of females. On average, in adult males, levels of testosterone are about 7 to 8 times as great as in adult females.[6] As the metabolism of testosterone in males is more pronounced, the daily production is about 20 times greater in men.[7][8] Females are also more sensitive to the hormone.[9]
14. Volek JS, Volk BM, Gómez AL, Kunces LJ, Kupchak BR, Freidenreich DJ, Aristizabal JC, Saenz C, Dunn-Lewis C, Ballard KD, Quann EE, Kawiecki DL, Flanagan SD, Comstock BA, Fragala MS, Earp JE, Fernandez ML, Bruno RS, Ptolemy AS, Kellogg MD, Maresh CM, Kraemer WJ. Whey protein supplementation during resistance training augments lean body mass. J Am Coll Nutr. 2013;32(2):122-35. PMID: 24015719

In a placebo-controlled study, 27 Division II football players received either a placebo or a ZMA supplement for a total of seven weeks during their scheduled spring practice. At the end of the seven weeks, the players taking the ZMA supplement had a 30 percent increase in testosterone, while the placebo group had a 10 percent decrease. The ZMA group also saw an 11.6 percent increase in strength, compared to only 4.6 percent in the placebo group.[7]
The group's 2010 clinical practice guidelines make it clear that "the threshold testosterone level below which symptoms of androgen deficiency and adverse health outcomes occur and testosterone administration improves outcomes in the general population is not known." They also clearly advise against screening men in the general population to avoid "labeling and medicalization of otherwise healthy men for whom testing, treatment, and monitoring would represent a burden with unclear benefit."
If a young man's low testosterone is a problem for a couple trying to get pregnant, gonadotropin injections may be an option in some cases. These are hormones that signal the body to produce more testosterone. This may increase the sperm count. Hedges also describes implantable testosterone pellets, a relatively new form of treatment in which several pellets are placed under the skin of the buttocks, where they release testosterone over the course of about three to four months. Injections and nasal gels may be other options for some men.