Hormones

Total Testosterone

Total testosterone measures the combined amount of bound and unbound testosterone in the blood. It is the primary male sex hormone responsible for muscle mass, bone density, red blood cell production, and reproductive function. Testosterone levels naturally peak in a man's late twenties and decline approximately 1-2% per year thereafter.

Optimal Ranges

Clinical (NHS) Range

8.64-29 nmol/L

nmol/L

Performance-Optimised Range

20-30 nmol/L

nmol/L

The clinical range defines what is considered medically “normal” — broad enough to cover 95% of the population. The performance range reflects where research and clinical experience suggest most people feel and function at their best.

Why It Matters

Why Testosterone matters for performance

Testosterone is the single most important hormone for male physical and mental performance. Low testosterone is associated with reduced muscle mass, increased body fat, poor sleep quality, low libido, and impaired cognitive function. Many men in their 30s and 40s have testosterone levels that are technically 'normal' but functionally suboptimal. Optimising the factors that support testosterone production — vitamin D, zinc, magnesium, sleep, and body composition — can meaningfully shift levels without medical intervention.

Symptoms

Signs your levels may be off

Low / Deficiency

  • Reduced muscle mass and strength
  • Increased body fat, especially visceral
  • Low libido and erectile dysfunction
  • Fatigue and brain fog
  • Depressed mood and irritability
  • Poor sleep quality

High / Excess

  • Acne and oily skin
  • Aggression and mood swings
  • Sleep apnoea
  • Elevated red blood cell count

Dietary Sources

Foods that support Testosterone levels

Zinc-rich foods (oysters, beef, pumpkin seeds)Healthy fats (olive oil, avocados, nuts)Cruciferous vegetables (broccoli, cauliflower)Eggs (whole, including yolk)Pomegranate

Supplementation

Evidence-based supplementation approach

Direct testosterone supplementation requires medical supervision (TRT). However, supporting nutrients that influence testosterone production include zinc (30 mg/day if deficient), magnesium (400 mg glycinate), vitamin D3, and ashwagandha (600 mg KSM-66). Prioritise sleep quality, resistance training, and maintaining body fat below 20% as foundational interventions.

Research

Key study

Testosterone and cortisol in relationship to dietary nutrients and resistance exercise

Volek JS, Kraemer WJ, Bush JA, et al.

Journal of Applied Physiology (1997)

DOI: 10.1152/jappl.1997.82.1.49

Related Biomarkers

Vitamins & Minerals

Vitamin D (25-OH)

Optimal: 100-150 nmol/L

Vitamins & Minerals

Magnesium (Serum)

Optimal: 0.85-1.0 mmol/L

Thyroid

TSH (Thyroid Stimulating Hormone)

Optimal: 1.0-2.0 mIU/L

Inflammation

Ferritin (Iron Stores)

Optimal: 80-150 ng/mL

Related Guides

Always Tired? The Blood Tests That Reveal Why

8 biomarkers behind fatigue

Complete Guide to Blood Tests for Men

What to test and why it matters

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This content is for educational purposes only and does not constitute medical advice. Your data suggests areas for optimisation, but any concerns should be discussed with a qualified healthcare professional. If your results flag values outside safe ranges, we recommend consulting your GP.