Low testosterone is often mistaken for a normal consequence of ageing, but persistent symptoms such as reduced sex drive, erectile dysfunction, low energy and loss of muscle strength should not simply be ignored.

Although testosterone levels naturally decline as men get older, noticeable changes can also be linked to lifestyle factors, underlying health conditions or problems affecting hormone production.

'There are many symptoms of low testosterone which patients may or may not be aware of. The "core" symptoms are closely related to low testosterone and include low libido, erectile dysfunction and loss of morning erections,' said Dr Areeb Mazhar, a GP with a special interest in testosterone deficiency and Clinical Director of Men's Medical Clinic.

'The majority of men don't experience all these symptoms as they get older, and we don't have to accept them as just "getting older".'

Testosterone plays an important role in male sexual health, sperm production, muscle maintenance, bone strength and overall well-being. Understanding the warning signs and knowing when to seek medical advice can help men identify potentially treatable problems.

What Are the Symptoms of Low Testosterone?

Low testosterone, also known as testosterone deficiency or hypogonadism, occurs when the body does not produce enough testosterone for normal function.

Symptoms can vary from person to person, but common signs include:

  • Reduced sex drive (low libido)
  • Erectile dysfunction
  • Loss of morning erections
  • Persistent tiredness or low energy
  • Reduced muscle mass and strength
  • Increased body fat
  • Low mood, anxiety or irritability
  • Difficulty concentrating or brain fog
  • Reduced motivation and confidence
  • Declining physical performance

However, experiencing one or more of these symptoms does not necessarily mean a man has low testosterone.

Many of these signs overlap with other conditions, including stress, depression, poor sleep, obesity and chronic illness. This is why doctors assess symptoms alongside blood test results rather than relying on symptoms alone.

When Should Men Get Their Testosterone Levels Checked?

Men should consider speaking with their GP if symptoms persist, affect their quality of life or interfere with relationships, work or daily activities.

A testosterone assessment may be appropriate for men experiencing:

  • Ongoing erectile difficulties
  • Significant reduction in sexual desire
  • Persistent fatigue despite adequate rest
  • Loss of muscle strength
  • Unexplained changes in mood
  • Difficulty conceiving

'Patients should be open and honest with their GP and educate themselves on low testosterone. Education and information allow them to advocate for their own health,' Dr Mazhar said.

'Education and information allow men to advocate for their own health.'

Men who are trying to start a family should be particularly mindful of symptoms, as hormonal problems may affect sperm production and fertility.

How Is Low Testosterone Diagnosed in the UK?

Doctors do not diagnose testosterone deficiency based on symptoms alone. Testosterone levels naturally fluctuate throughout the day and may temporarily fall because of illness, poor sleep, stress or intense physical activity.

Testing usually begins with a blood test taken in the morning, when testosterone levels are typically highest.

A doctor may initially check:

  • Total testosterone levels
  • Free testosterone levels
  • Sex hormone-binding globulin (SHBG)
  • Albumin levels

Free testosterone refers to the portion of testosterone available for the body to use and can provide additional information when total testosterone results are unclear.

If results suggest testosterone deficiency, doctors usually repeat testing at another time to confirm the findings.

'Two blood tests should be done at different times,' Dr Mazhar explained. 'This helps us to track trends or improvements or worsening results over a period of time.'

Further investigations may include checking other hormones, such as luteinising hormone (LH), follicle-stimulating hormone (FSH) and prolactin, to identify whether the problem originates in the testes or the pituitary gland.

What Causes Low Testosterone?

Low testosterone can have many causes, ranging from lifestyle factors to medical conditions.

Weight gain and metabolic health

One of the most common contributors is metabolic syndrome, which is associated with obesity, insulin resistance and other health problems.

Excess body fat can interfere with hormone regulation and reduce testosterone production.

Poor sleep and stress

Sleep deprivation and conditions such as obstructive sleep apnoea can affect testosterone levels. Chronic stress may also influence hormone balance and contribute to symptoms such as fatigue and low mood.

Chronic illnesses

Conditions, including poorly controlled diabetes and other long-term health problems, may affect testosterone production.

Medications and substance use

Certain medications, excessive alcohol intake and previous anabolic steroid use can suppress natural testosterone production.

Problems affecting the testes or pituitary gland

Less commonly, low testosterone may result from testicular injury, previous surgery, infections or disorders affecting the pituitary gland, which controls hormone signals in the body.

Identifying the underlying cause is important because some men may improve testosterone levels by addressing the root issue rather than needing hormone replacement.

Can Low Testosterone Affect Fertility?

Testosterone is essential for male reproductive health, but fertility depends on more than testosterone levels alone.

Low testosterone may contribute to reduced sperm production, lower libido and erectile difficulties. However, testosterone measured in a blood test does not always reflect the testosterone levels inside the testes, where sperm production takes place.

Men experiencing fertility problems alongside symptoms of low testosterone should receive a comprehensive reproductive assessment.

One important consideration is that testosterone replacement therapy (TRT) can actually reduce fertility. While it may benefit men with confirmed testosterone deficiency and persistent symptoms, it is not suitable for men who are actively trying to conceive.

'[TRT] suppresses the hormones that stimulate sperm production and can significantly reduce fertility,' said Dr Yusuf Beebeejaun MRCOG, Medical Director at CREATE Fertility St Paul's, IVI RMA UK.

What Treatments Are Available for Low Testosterone?

Treatment depends on the cause, severity of symptoms and a man's personal circumstances.

Lifestyle changes

For some men, improving health and lifestyle factors can help increase testosterone levels naturally.

Approaches may include:

  • Losing excess weight
  • Regular resistance and aerobic exercise
  • Improving sleep quality
  • Managing stress
  • Treating underlying health conditions
  • Reducing excessive alcohol consumption

Testosterone replacement therapy (TRT)

TRT may be considered for men with confirmed testosterone deficiency who continue to experience symptoms despite addressing reversible causes.

Treatment options available in the UK include testosterone gels and injections. The choice depends on individual needs, preferences and medical factors.

However, TRT requires careful assessment and monitoring. It is not recommended simply as a treatment for tiredness, ageing or improving athletic performance.

Doctors may monitor factors such as blood counts and prostate health before and during treatment.

Common Myths About Low Testosterone

Myth: Low testosterone is unavoidable as men age

While testosterone levels naturally decline with age, significant symptoms should not automatically be dismissed as part of getting older.

Myth: Testosterone treatment is an anti-ageing cure

TRT is designed for men with clinically diagnosed testosterone deficiency. It is not a general solution for low energy, poor motivation or normal ageing.

Myth: Higher testosterone always means better fertility

This is incorrect. Taking testosterone replacement can reduce sperm production and may make conception more difficult.

Low testosterone is not something men should self-diagnose or ignore. If symptoms persist or begin affecting daily life, relationships or fertility, speaking to a GP is the best first step. Early assessment can help identify the underlying cause and ensure men receive the most appropriate treatment, whether that involves lifestyle changes, further investigations or, where appropriate, testosterone replacement therapy.