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Why is testosterone important?

Testosterone is a key hormone that plays a major role in men’s health. It helps support muscle growth, strength, sex drive, mood, and overall energy levels¹. Think of it as one of the body’s main 'performance regulators.'

As men age, testosterone levels naturally decline - but stress, lifestyle, and certain health conditions can cause levels to drop faster than expected.

Recognising the signs of low testosterone early is important as a lack of it can affect both your physical and mental health.

Signs of low testosterone in men

Grafik: Heather Ainsworth

1. Reduced libido

Low testosterone can directly affect your sex drive (libido)². Men with reduced hormone levels often notice a decreased interest in sexual activity or intimacy, which can impact relationships and overall quality of life.

2. Loss of body hair

Testosterone helps regulate hair growth³. A drop in levels can lead to thinning or loss of hair on the face, chest, or body over time.

3. Fatigue

Feeling unusually tired (fatigue), even after enough sleep, is a common symptom of low testosterone⁴. It can reduce energy levels and make everyday tasks feel more exhausting than usual.

4. Depressed mood

Hormonal changes can influence brain chemistry. Men with low testosterone may experience irritability, sadness, or even Depressionen⁵, sometimes without realising the hormonal link.

5. Loss of muscle mass and strength

Testosterone plays a key role in building and maintaining muscle¹. Lower levels can make it harder to gain or retain muscle, and strength may decline over time.

6. Increase in body fat

A drop in testosterone can contribute to an increase in body fat, especially around the stomach⁶. This can also increase the chance of metabolic issues such as insulin resistance.

7. Difficulty concentrating or brain fog

Low testosterone may affect cognitive function, making it harder to focus, remember details, or stay mentally sharp during the day⁷.

8. Increase in breast tissue

Low testosterone levels can lead to the development of excess breast tissue (gynecomastia) in men⁸. This is often a gradual change but can be noticeable and sometimes uncomfortable.

9. Erectile dysfunction

Testosterone helps regulate sexual function, including erections. Low levels may make it harder to achieve or maintain an erection⁹, though other health factors can also contribute.

If you think you may have low testosterone, the first step is to speak with a doctor or healthcare professional.

Testing isn’t something you can accurately do at home - your doctor will order a simple blood test that measures your testosterone levels, usually taken in the morning when levels are highest.

Depending on the results, they may repeat the test or check other hormones to get a clearer picture of what’s going on.

From there, your doctor can discuss your options, which may include lifestyle changes, further testing, or potential treatment.

Testosterone levels can vary from person to person but for adult men, total testosterone levels typically fall between 300 and 1,000 ng/dL (nanograms per decilitre)².

However, what matters most is not just the number, but how you feel. Some men may experience symptoms even if their levels are technically within the normal range.

That’s why it’s important to look at both your test results and your day-to-day symptoms if something feels off.

Low testosterone is a common hormonal imbalance that can impact energy, mood, muscle strength, and overall wellbeing - especially in men over 30.

Symptoms to watch for include fatigue, reduced libido, loss of muscle mass, increased body fat (particularly around the stomach), mood changes such as irritability or depression, loss of body hair, low motivation, and trouble concentrating.

If these signs sound familiar, it may be time to speak with your doctor about testing and treatment options.

1. Rojas-Zambrano et al: Benefits of Testosterone Hormone in the Human Body

2. Sizar et al: Male Hypogonadism

3. Inui S, Itami S: Androgen actions on the human hair follicle

4. Cruickshank et al: The effects and safety of testosterone replacement therapy for men with hypogonadism

5. Shores et al: Low testosterone levels predict incident depressive illness in older men

6. Kelly et al: Testosterone and obesity

7. Cherrier et al: Testosterone treatment of men with mild cognitive impairment and low testosterone levels

8. Robeva et al: Causes and Metabolic Consequences of Gynecomastia in Adult Patients

9. Martínez-Jabaloyas et al: Testosterone levels in men with erectile dysfunction