What Are Normal Testosterone Levels?
Testosterone is the primary male sex hormone, though it plays important roles in both men and women. Understanding what constitutes "normal" testosterone levels is essential for anyone tracking their health, particularly those on testosterone replacement therapy (TRT) or investigating symptoms of hormonal imbalance.
Total testosterone is measured in nanomoles per litre (nmol/L) in Australia, though many international references use nanograms per decilitre (ng/dL). The reference ranges vary by laboratory, age, and time of day the blood was drawn. Here, we break down exactly what you should expect at every stage of life.
Testosterone Levels in Men by Age Group
Testosterone production peaks during late adolescence and early adulthood, then gradually declines at a rate of roughly 1–2% per year after age 30. This decline is sometimes called "andropause" or late-onset hypogonadism.
Ages 18–25: Peak Production
Young adult men typically have the highest natural testosterone levels. Reference ranges for this age group generally fall between 12–31 nmol/L (346–893 ng/dL). Most men in this bracket sit comfortably in the mid-to-upper range without intervention.
Ages 26–35: Plateau Phase
Testosterone remains relatively stable through the late twenties and into the early thirties. Typical levels range from 11–28 nmol/L (317–807 ng/dL). The decline has begun but is usually imperceptible at this stage.
Ages 36–45: Early Decline
By the late thirties and early forties, many men notice the first symptoms of declining testosterone — reduced energy, changes in body composition, and decreased libido. Levels typically range from 9.5–25 nmol/L (274–720 ng/dL).
Ages 46–55: Noticeable Changes
The decline accelerates slightly during this decade. Average levels drop to 8.5–23 nmol/L (245–663 ng/dL). This is the age group where TRT discussions become most common with healthcare providers.
Ages 56–65: Significant Decline
Men in this bracket often experience levels of 7.5–21 nmol/L (216–605 ng/dL). Symptoms like fatigue, muscle loss, cognitive changes, and sexual dysfunction become more prevalent.
Ages 65+: Lower Baseline
Older men may have testosterone levels as low as 6.5–18 nmol/L (187–519 ng/dL). However, the clinical significance of these levels is debated — some men function well at lower levels while others experience significant symptoms.
Testosterone Reference Ranges: Australian vs International
Australian pathology labs typically report testosterone in nmol/L, with most using a reference range of approximately 8–29 nmol/L for adult men. However, these ranges represent the statistical distribution of all tested men, including those who may already have suboptimal levels.
To convert between units: 1 nmol/L = 28.8 ng/dL. So the Australian lower limit of 8 nmol/L equals roughly 230 ng/dL.
Many progressive endocrinologists and men's health specialists consider optimal (not just "normal") testosterone to be in the 15–25 nmol/L (432–720 ng/dL) range, where most men report feeling their best.
Why Reference Ranges Can Be Misleading
Standard reference ranges are derived from the general population, including men who are overweight, sedentary, or chronically stressed — all factors that suppress testosterone. This means the "normal" range may actually include suboptimal levels. This is why tracking your individual trend over time is more valuable than a single snapshot compared to a population range.
Free Testosterone vs Total Testosterone
Total testosterone includes all testosterone in your blood — both bound and unbound. Approximately 98% of testosterone is bound to either sex hormone-binding globulin (SHBG) or albumin. Only about 2–3% circulates as free testosterone, which is the biologically active form that your cells can use.
You can have a normal total testosterone level but low free testosterone if your SHBG is elevated. Common causes of high SHBG include:
- Ageing
- Liver conditions
- Hyperthyroidism
- Certain medications (particularly oral estrogen)
- Low body weight
This is why a comprehensive hormone panel should include total testosterone, free testosterone, and SHBG at minimum.
Testosterone Levels in Women
Women produce significantly less testosterone than men, but it remains crucial for energy, libido, bone density, and muscle maintenance. Normal female testosterone ranges are typically 0.5–2.4 nmol/L (14–69 ng/dL), though optimal levels for symptom relief may differ from lab reference ranges.
Women experiencing perimenopause or menopause often see testosterone decline alongside estrogen and progesterone, contributing to fatigue, low libido, and mood changes.
Factors That Affect Your Testosterone Levels
Before panicking about a single test result, consider these variables:
Time of Day
Testosterone follows a circadian rhythm, peaking between 6–9 AM and dropping by 20–30% by late afternoon. Always test in the morning for consistent, comparable results.
Sleep Quality
Poor sleep can reduce testosterone by 10–15% in just one week. Studies show that men sleeping fewer than 5 hours per night have significantly lower levels than those getting 7–8 hours.
Body Composition
Excess body fat, particularly visceral fat, contains aromatase enzymes that convert testosterone to estrogen. Losing as little as 5–10% of body weight can significantly increase testosterone levels in overweight men.
Stress and Cortisol
Chronic stress elevates cortisol, which directly suppresses testosterone production through the hypothalamic-pituitary-gonadal (HPG) axis. Managing stress through exercise, meditation, or lifestyle changes can help maintain healthy levels.
Exercise
Resistance training and high-intensity interval training (HIIT) acutely boost testosterone. However, overtraining and excessive endurance exercise can actually suppress levels through elevated cortisol.
Diet and Nutrition
Key nutrients for testosterone production include zinc, vitamin D, magnesium, and healthy fats (particularly monounsaturated and saturated fats). Extremely low-fat diets have been associated with reduced testosterone levels.
When to See a Doctor About Low Testosterone
Consider seeking medical evaluation if you experience multiple symptoms alongside low test results:
- Persistent fatigue not explained by sleep or lifestyle
- Decreased libido or erectile dysfunction
- Loss of muscle mass despite regular exercise
- Increased body fat, particularly abdominal
- Mood changes: irritability, depression, or brain fog
- Decreased bone density
A diagnosis of hypogonadism typically requires two morning blood tests showing low testosterone, combined with clinical symptoms. In Australia, your GP can order these tests, often with a Medicare rebate if clinically indicated.
How BloodTrack Helps You Monitor Testosterone
Rather than relying on a single lab result, BloodTrack lets you visualise your testosterone trend over months and years. You can:
- Track total and free testosterone alongside SHBG, estradiol, and other markers
- See your levels plotted against age-appropriate ranges, not just generic lab ranges
- Correlate testosterone with lifestyle factors like sleep, exercise, and body composition
- Monitor TRT protocols with injection logging, peak/trough predictions, and dose optimisation tools
- Share visual reports with your healthcare provider for more productive consultations
Understanding where your testosterone sits relative to your age — and how it's trending — is far more valuable than any single number.
