Testosterone peaks in men's early 20s and then declines at roughly 1–2% per year. Testosterone tends to decline with age, and population data show levels in American men have been falling over time; low levels can cause symptoms including erectile dysfunction [1]. Yet most never get tested or attribute the symptoms to 'just getting older'.
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Signs of Low Testosterone
- •Reduced sex drive (libido) — often the first and most noticeable sign
- •Erectile dysfunction or reduced erection quality
- •Fatigue and low energy despite adequate sleep
- •Loss of muscle mass and increased body fat (especially around the abdomen)
- •Mood changes — irritability, low motivation, depression
- •Difficulty concentrating and brain fog
- •Reduced bone density (increases fracture risk)
- •Decreased body and facial hair
- •Hot flashes and night sweats
- •Reduced ejaculate volume
Many of these symptoms overlap with other conditions including thyroid problems, depression, and sleep apnoea. A blood test is the only way to confirm low testosterone.
What Are Normal Testosterone Levels?
Total testosterone is measured in nanomoles per litre (nmol/L) or nanograms per decilitre (ng/dL):
- •Typical adult male reference range: roughly 300–1,000 ng/dL (about 10–35 nmol/L); exact ranges vary by laboratory
- •Low testosterone: below 10 nmol/L (300 ng/dL)
- •Borderline: 10–12 nmol/L with symptoms warrants discussion with a doctor
- •Always test in the morning (7–10am) — testosterone is highest then
Common Causes of Low Testosterone
- •Normal ageing — the most common cause
- •Obesity — fat cells convert testosterone to oestrogen
- •Chronic stress — sustained cortisol suppresses testosterone production
- •Poor sleep — testosterone is produced during REM sleep
- •Type 2 diabetes and metabolic syndrome
- •Overtraining without adequate recovery
- •Excessive alcohol consumption
- •Certain medications (opioids, steroids, some antidepressants)
Natural Ways to Optimise Testosterone
1. Resistance Training
Compound lifts (squats, deadlifts, bench press) trigger the largest testosterone response of any exercise. Aim for 3 sessions per week, focusing on multi-joint movements with challenging weights and adequate rest.
2. Optimise Sleep
7–9 hours per night in a cool, dark room. In a University of Chicago study, one week of restricting sleep to about five hours a night lowered testosterone in healthy young men [4].
3. Key Nutrients
- •Zinc — directly required for testosterone synthesis; oysters, red meat, pumpkin seeds
- •Vitamin D — in a one-year trial of overweight men with low vitamin D, supplementation raised total testosterone from 10.7 to 13.4 nmol/L [2]
- •Magnesium — deficiency is linked to lower testosterone
- •Ashwagandha: some trials suggest a rise in testosterone (in one 8-week trial of 57 young men starting resistance training, +96 ng/dL versus +18 ng/dL on placebo [3]), but the evidence is limited and results vary
4. Reduce Body Fat
Adipose (fat) tissue contains aromatase, an enzyme that converts testosterone to oestrogen. Losing abdominal fat is one of the most effective ways to raise testosterone naturally.
When to Consider Testosterone Replacement Therapy
If lifestyle approaches don't resolve symptoms and blood tests confirm consistently low levels, testosterone replacement therapy (TRT) may be appropriate, as decided with your doctor. This is a decision to make with an endocrinologist or urologist who can properly monitor levels, red blood cell count, and prostate health during treatment.
How to Test Testosterone Properly
Testosterone testing is frequently done incorrectly, leading to misleading results. The details matter:
- •Test in the morning (guidelines advise early-morning samples), because testosterone is highest early in the day and falls later
- •Test twice before acting on results — testosterone varies significantly day to day; two low readings on different mornings confirm deficiency
- •Request both total AND free testosterone — total testosterone can appear normal while free (bioavailable) testosterone is deficient
- •Also test LH and FSH — these determine whether low testosterone is primary (testicular) or secondary (pituitary) in origin, affecting treatment approach
- •Test SHBG (sex hormone binding globulin) — high SHBG reduces free testosterone even when total is normal
The Testosterone-Oestrogen Balance: What Men Rarely Hear
As men age, the enzyme aromatase (found in fat cells) converts increasing amounts of testosterone to oestradiol (a form of oestrogen). This dual change — declining testosterone and rising oestradiol — explains many low-T symptoms better than testosterone alone.
Men with high body fat typically show high aromatase activity. Weight loss is therefore one of the most effective natural ways to shift this balance — reducing both the conversion of testosterone and improving free testosterone availability.
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Low Testosterone and Prostate Health
Many men worry that optimising testosterone will harm their prostate. The evidence does not support this concern. Testosterone does not cause prostate cancer — a landmark 2006 study in the New England Journal of Medicine found no increased prostate cancer risk with testosterone therapy in properly selected men. However, testosterone can stimulate existing prostate cancer, which is why a baseline PSA test is essential before any testosterone intervention.
Interestingly, extremely low testosterone may actually be associated with more aggressive prostate cancer — suggesting that some testosterone is protective rather than harmful. Men with BPH who optimise testosterone through lifestyle do not typically experience symptom worsening. The relationship is complex, and any testosterone therapy should be accompanied by 6-monthly PSA monitoring.
How Long Before You See Results?
- •Libido: may improve over weeks once any underlying cause is addressed
- •Energy and mood: may improve over weeks with better sleep and resistance training
- •Body composition changes (muscle gain, fat loss): take months of consistent training and nutrition
- •Erectile function: improvement is slower and less predictable, because testosterone is only one of many factors in ED
- •PSA and prostate effects: monitor at 6 months if starting TRT
Frequently Asked Questions
What testosterone level is too low for a man over 40?
The clinical definition of hypogonadism (low testosterone) is below 10 nmol/L (300 ng/dL) on two separate morning tests, accompanied by symptoms. However, many men experience significant symptoms at levels of 10–15 nmol/L — the 'low-normal' range. There is no agreed 'optimal' level above the normal range; treatment decisions depend on symptoms and repeated morning measurements.
Can low testosterone cause weight gain?
Yes — low testosterone and weight gain form a self-reinforcing cycle. Low testosterone reduces muscle mass and metabolic rate, promoting fat accumulation. Increased body fat raises aromatase activity, converting more testosterone to oestrogen and further lowering testosterone. Breaking this cycle requires both addressing the testosterone deficiency and reducing body fat — neither is fully effective without the other.
Is testosterone replacement therapy safe?
TRT is safe for appropriately selected men under proper medical supervision. Key monitoring requirements: PSA every 6 months (testosterone can stimulate existing prostate cancer), haematocrit (testosterone raises red blood cell production, increasing clot risk if levels rise too high), and oestradiol (excess testosterone conversion to oestrogen causes side effects). TRT should never be started without baseline bloods and prostate assessment.
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When to Get Tested: The Morning Rule
Testosterone follows a daily rhythm, peaking in the morning and falling later in the day. This is not a minor variation — an afternoon result of 8 nmol/L (230 ng/dL) can correspond to a morning level above the clinical threshold. All diagnostic testosterone testing should be performed before 10am on two separate occasions. A single afternoon result that falls in the low-normal range cannot be used to confirm or exclude hypogonadism.
True Hypogonadism vs. Age-Related Decline
Testosterone tends to decline gradually with age. In older age, many men have levels well below their peak. Clinical hypogonadism, however, is defined as a total testosterone below 10 nmol/L (300 ng/dL) on two morning samples, accompanied by symptoms. Men in the 10–15 nmol/L range may experience significant symptoms without meeting the formal diagnostic threshold — a situation sometimes called 'relative hypogonadism.' Treatment decisions in this grey zone should weigh symptom burden, free testosterone, and response to lifestyle intervention.
Free Testosterone vs. Total Testosterone
Total testosterone includes both the free fraction (~2%) and the 98% bound to sex hormone-binding globulin (SHBG) and albumin. SHBG-bound testosterone is biologically inactive — it cannot enter cells. Free testosterone is the clinically relevant fraction. Men with elevated SHBG — common with ageing, liver disease, hyperthyroidism, and certain medications — may have a normal total testosterone but significantly reduced free testosterone and full symptomatic hypogonadism. Always request free testosterone or calculated free T (using SHBG and albumin) alongside total T.
Secondary Causes of Low Testosterone
- •Obesity: adipose tissue converts testosterone to oestrogen via aromatase — higher body fat means lower testosterone
- •Obstructive sleep apnea: disrupted sleep and low oxygen at night are linked to lower testosterone
- •Opioid medications: mu-receptor agonists suppress GnRH release, lowering LH and testosterone — opioid-induced androgen deficiency (OPIAD) is underdiagnosed
- •Chronic illness: type 2 diabetes, chronic kidney disease, and HIV independently suppress testosterone
- •Anabolic steroid history: prior supraphysiological exogenous androgens cause prolonged pituitary-gonadal suppression
- •Prolactin-secreting tumours: even small pituitary adenomas can abolish LH pulsatility — always check prolactin in hypogonadal men
TRT Forms: Injections, Gels, and Pellets
Testosterone replacement therapy is available in several delivery systems, each with different pharmacokinetics and practical tradeoffs. Intramuscular injections (testosterone cypionate or enanthate) produce supraphysiological peaks followed by troughs — typically dosed weekly or every two weeks. Subcutaneous pellets (implanted every few months): minimal daily burden, though levels change over the cycle Topical gels and creams produce stable daily levels but carry transfer risk to partners and children. Transdermal patches offer convenience but have higher skin-reaction rates. The right form depends on adherence profile, relationship circumstances, and tolerance for peaks and troughs.
Optimising Testosterone Naturally Before Considering TRT
- •Sleep 7–9 hours: testosterone is synthesised predominantly during deep sleep — each hour of sleep deprivation measurably reduces morning testosterone
- •Resistance training: compound lifts (squat, deadlift, bench) acutely raise testosterone and improve receptor sensitivity
- •Weight loss: 10% body weight reduction raises testosterone by approximately 15% in obese hypogonadal men
- •Zinc repletion: zinc is a cofactor for testosterone synthesis — in a small study, six months of zinc supplementation raised testosterone from 8.3 to 16.0 nmol/L in marginally zinc-deficient older men [5]; deficiency is common in men eating low red meat or high-phytate diets
- •Vitamin D optimisation: Vitamin D receptors are present on Leydig cells; in a one-year trial, vitamin D supplementation raised total testosterone in overweight men who started with low vitamin D [2]
- •Alcohol reduction: even moderate alcohol consumption (>14 units/week) suppresses testosterone by ~7%
If your testosterone is borderline (10–14 nmol/L) with symptoms, spend 90 days optimising sleep, resistance training, and zinc before requesting TRT. Many men recover into the normal range without medication.
Frequently Asked Questions
What time should I get my testosterone tested?
Before 10am, fasting or with only water. Testosterone peaks in the morning and falls later in the day. An afternoon test in the low-normal range does not confirm hypogonadism and does not accurately represent your testosterone status. Two morning tests on separate days are required for a diagnosis of hypogonadism.
Can TRT cause prostate cancer?
Current evidence does not support TRT causing de novo prostate cancer. The 'testosterone fuels prostate cancer' concern stems from decades-old observations in castrated men, not from modern TRT data. However, TRT can accelerate pre-existing prostate cancer. A baseline PSA and DRE are required before starting TRT, with PSA monitoring every 6 months thereafter. Active or suspected prostate cancer remains an absolute contraindication to TRT. Men on TRT with PSA rising more than 1 ng/mL per year warrant urology referral for prostate evaluation.
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