Testosterone Levels by Age: What Is Normal and What Is Optimal

Testosterone plays important roles in both men and women, influencing muscle mass, bone density, energy, mood, libido, and cardiovascular health. Understanding how levels change with age — and what constitutes normal versus optimal — is essential for long-term health.

How Testosterone Changes With Age

In men, testosterone peaks between ages 18 and 25, then declines at approximately 1–2% per year from age 30. By age 50, many men have levels 20–30% lower than their peak. In women, testosterone is produced at much lower levels and also declines with age, with a pronounced drop around menopause.

What Are Normal Levels?

In Australia, the standard reference range for total testosterone in men is 8–30 nmol/L. The Endocrine Society of Australia defines deficiency as consistently below 8 nmol/L with symptoms. Average levels by decade: 20s (15–25 nmol/L), 30s (13–22), 40s (11–20), 50s (10–18), 60s (8–16), 70+ (7–14).

Normal vs Optimal

Standard ranges include people who are overweight, sedentary, and metabolically unhealthy. Being "normal" does not mean optimal. Many practitioners suggest men function best in the upper third of the range for their age. However, symptoms matter more than numbers — a man at 12 nmol/L who feels energetic does not necessarily need intervention.

Total vs Free Testosterone

Only about 2–3% of testosterone is biologically active (free). SHBG increases with age, meaning free testosterone can decline more steeply than total testosterone. If your total is in the lower half with symptoms, request free testosterone and SHBG testing.

Modifiable Factors

Obesity is one of the strongest modifiable risk factors — adipose tissue converts testosterone to oestrogen via aromatase. Research shows sleeping only five hours per night for one week reduces testosterone by 10–15% in young men. Chronic stress, excessive endurance exercise, and alcohol also suppress production.

When to Seek Help

In Australia, testosterone replacement therapy (TRT) requires documented hypogonadism (total testosterone < 8 nmol/L on two morning samples) plus clinical symptoms. Tracking your levels yearly reveals your hormonal trajectory and allows early intervention through lifestyle changes.

References

1. Handelsman DJ, et al. Age-specific population centiles for androgen status in men. Eur J Endocrinol. 2015;173(6):809–817.
2. Endocrine Society of Australia. Position Statement on Male Hypogonadism. ESA, 2016.
3. Leproult R, Van Cauter E. Effect of 1 week of sleep restriction on testosterone levels. JAMA. 2011;305(21):2173–2174.
4. Corona G, et al. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism. Eur J Endocrinol. 2013;168(6):829–843.