Signs of Low Testosterone in Men

Testosterone is the primary male sex hormone. It plays a critical role in energy, mood, muscle mass, bone density, fat distribution, libido, and cognitive function. When levels drop below the normal range, the effects can be wide-ranging and often develop so gradually that many men don't recognise them for what they are.

According to Healthy Male (Australia's national men's health organisation), testosterone is essential for normal development and overall wellbeing, and androgen deficiency can have wide-ranging effects on both physical and mental health.

Common signs and symptoms of low testosterone

Low testosterone (clinically known as hypogonadism or androgen deficiency) doesn't always present the same way. However, the most commonly reported symptoms include:

• Persistent fatigue — A deeper, unrelenting lack of energy that isn't explained by poor sleep or a busy schedule.
• Reduced libido — A noticeable drop in sexual desire not explained by stress, relationship factors, or medication side effects.
• Erectile difficulties — While testosterone alone doesn't cause erections, low levels can contribute to difficulty achieving or maintaining them. The Australian Government's Healthdirect notes that low testosterone is a recognised physical cause of erectile dysfunction.
• Mood changes — Increased irritability, low mood, difficulty concentrating, and symptoms resembling depression or anxiety.
• Loss of muscle mass — Difficulty building or maintaining muscle despite consistent training and adequate protein intake.
• Increased body fat — Particularly around the midsection, sometimes accompanied by breast tissue development (gynaecomastia).
• Poor sleep — Insomnia or disrupted sleep patterns that don't respond to standard sleep hygiene improvements.
• Brain fog — Difficulty with concentration, memory, and mental sharpness.

When should you get tested?

If you've been experiencing several of these symptoms persistently — over weeks or months rather than just a bad week — it's worth having a conversation with a GP. The only way to confirm low testosterone is through a blood test.

Testing involves a fasting morning blood draw (testosterone levels are highest in the morning and can drop significantly later in the day). As Healthy Male explains, the normal testosterone reference range for healthy young adult men extends across a wide range (8–30 nmol/L), so at least two separate low readings are needed for a diagnosis. Your GP will also check free testosterone, SHBG, LH, FSH, and other markers to determine the cause.

What causes low testosterone?

Testosterone naturally declines at roughly 1–2% per year after age 30. But age isn't the only factor. According to evidence reviewed by Healthy Male, factors that affect testosterone include:

• Obesity and excess body fat — Being overweight is one of the strongest predictors of low testosterone. Weight loss can significantly increase levels.
• Type 2 diabetes — Men with diabetes are more likely to have low testosterone, and vice versa.
• Chronic stress and poor sleep — Both directly suppress testosterone production.
• Certain medications — Particularly opioid painkillers and some antidepressants.
• Genetic conditions — Including Klinefelter syndrome, which affects at least 1 in 600 Australian men and is significantly underdiagnosed.

Research has also shown population-level testosterone declining decade over decade. A Healthy Male review of the evidence suggests this is likely driven by increasing rates of obesity and chronic disease rather than environmental factors alone.

What are the treatment options?

If blood work confirms clinically low testosterone and you're experiencing symptoms, your GP may discuss testosterone replacement therapy (TRT). In Australia, TRT must be prescribed by a medical practitioner — usually a GP after evaluation, or by an endocrinologist or urologist. The TGA regulates testosterone as a Schedule 4 prescription medicine.

TRT involves regular monitoring via blood tests to track testosterone levels, haematocrit, PSA, and liver function. It is not a lifestyle supplement — it's a medical treatment with real benefits for men who need it. Your GP will also discuss alternatives like enclomiphene for men who want to preserve fertility.

For a transparent breakdown of what TRT costs in Australia, see our guide: TRT Cost in Australia.

The bottom line

Low testosterone is a real medical condition with effective treatment — but it's also frequently over-diagnosed by online clinics pushing unnecessary prescriptions. The right approach is to get proper blood work, see a qualified GP, and make an informed decision based on your actual levels and symptoms.