Where your DNA places you among other people, and the studies behind it.
Not tailored to your result, and not medical advice
Reduce Excess Visceral Fat: Fat tissue raises aromatase activity in proportion to fat mass, converting testosterone into estrogens, and inflammatory signals from fat such as IL-6, IL-1 beta and TNF-alpha have been found to suppress gonadotropin release, alongside an attenuated LH pulse amplitude. In a pooled analysis, a meal-replacement low-calorie diet produced modest weight loss of about 10 percent with only a mild rise in total testosterone of roughly 3 nmol/L; the larger rise of about 5.75 nmol/L came from weight losses above 15 percent, which in these studies were achieved mainly through bariatric surgery rather than diet. Reduction in visceral fat measured by MRI was positively associated with the size of the rise, so where fat is lost appears to matter and not only how much. Nearly all of the modifiable-factor evidence for testosterone comes from studies in men. International Journal of Molecular Sciences (PMC)
Protect Your Sleep Duration: In a laboratory study, 10 healthy men with a mean age of 24 spent 8 nights with 5 hours in bed following a rested baseline of 10 hours. Daytime testosterone fell by 10 to 15 percent, from 18.4 to 16.5 nmol/L averaged across waking hours, with the widest gap between 2pm and 10pm. Short sleep is one of the few everyday exposures shown to shift testosterone measurably within a single week. The sample was small, so treat the size of the effect as approximate rather than precise. JAMA (PMC)
Eat Enough For Your Training: Training hard while under-eating, described in sports medicine as low energy availability, is associated with suppressed testosterone rather than raised. Male endurance runners covering 81 km a week had total testosterone of 9.2 nmol/L against 16.2 nmol/L in inactive men, alongside lower energy availability of 27 versus 45 kcal per kg of fat-free mass per day. In a series of 24 elite distance runners all exceeding 100 km a week, 40 percent had low testosterone, and bone injuries were 4.5 times more common in that group. Matching food intake to training load appears to matter as much as the training itself. European Journal of Translational Myology (PMC)
Skip Testosterone Booster Supplements: An analysis of the best-selling online testosterone boosting supplements identified 19 distinct ingredients, and a literature review of the 10 most common of them turned up 191 studies, only 19 percent of which involved humans at all. Among the 37 human studies, 30 percent reported a rise in testosterone, 3 percent a fall, 46 percent no effect and 22 percent were indeterminate. After filtering suspicious customer reviews, reports of increased libido dropped by 91 percent and reports of improved strength or endurance by 93 percent. The authors concluded that rigorous evidence supporting these products is lacking, and that is the honest state of the evidence for this category. The Journal of Sexual Medicine (PMC)
Avoid Non-Prescribed Androgens: Androgens taken from outside the body, including anabolic steroids sold for muscle gain, exert negative feedback on GnRH and LH release, lower intratesticular testosterone and blunt FSH, reducing or halting sperm production in a dose and duration dependent way. In male contraceptive trials, the median time to recover a sperm concentration of 20 million per mL after stopping was 3 to 6 months, with roughly 67 percent of men recovered by 6 months and 90 percent by 12. After anabolic steroid use, case reports describe recovery over 4 to 12 months, and in some men 24 to 30 months. Longer exposure and older age were associated with slower recovery, and persistent symptoms or fertility concerns are worth raising with a clinician. Asian Journal of Andrology (PMC)
How much of this is genetic?
Genetics explains 50% of why people differ in this trait. The rest is environment, daily habits and chance.
Heritability estimate: Twin studies estimate heritability of circulating testosterone in a moderate range, roughly 40-60% and typically higher in males (e.g. Harris et al., Behav Genet 1998; Framingham Heart Study). Its polygenic, strongly sex-specific architecture was characterized by Ruth et al., Nature Medicine 2020
Background and further reading
Testosterone is the principal androgen (male sex steroid) but is present and biologically active in everyone. It is produced mainly in the testes in men and in the ovaries and adrenal glands in women, under control of the hypothalamic-pituitary-gonadal axis. It influences muscle and bone mass, red-blood-cell production, libido, mood, and reproductive function. In the bloodstream most testosterone is bound to sex hormone-binding globulin (SHBG) and albumin; only the small unbound (free) fraction is biologically available to tissues. Levels vary widely between individuals, across the day (typically highest in the morning), and across the lifespan, gradually declining with age in men.
Genetic Basis: Twin and family studies place the heritability of circulating testosterone in a moderate range, and large genome-wide association studies have confirmed it is highly polygenic. A key finding is that the genetic architecture is strongly sex-specific: variants that raise testosterone in men are largely different from those in women, and the genetic correlation between male and female testosterone is close to zero. One of the strongest and most consistent signals is at the SHBG gene, because variants that change SHBG levels shift how much testosterone is bound versus free. Other loci implicate genes involved in steroid synthesis and androgen metabolism such as JMJD1C, FKBP4, and the FAM9B region on the X chromosome. Because so many small-effect variants are involved, a polygenic score captures only part of the inherited component.
Environmental and Physiological Factors: Many non-genetic factors move testosterone up or down and often outweigh genetics on any given day. Age is a major driver, with a slow decline in men from roughly the third decade onward. Higher body fat is associated with lower testosterone in men, while resistance exercise, adequate sleep, and recovery from acute illness can raise it. Chronic illness, poor sleep, heavy alcohol use, certain medications, and significant psychological stress can lower it. In women, conditions such as polycystic ovary syndrome are associated with higher androgen levels. Because a single blood measurement is affected by time of day, recent activity, and health status, a genetic tendency describes only a long-run baseline, not a fixed value.
The published research behind your score, and the variants it draws on.
10 published scores from 4 studies
The testosterone score combines 10 polygenic scores drawn from 4 published studies.
Flynn E (2020). Sex-specific genetic effects across biomarkers. Eur J Hum Genet: 8k
These traits are influenced by some of the same genes and variants as this one
Content updated August 2026.
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