Testosterone is the main male sex hormone, but it does far more than drive libido. It supports energy, mood, muscle mass, bone strength and concentration. Levels fall naturally with age — roughly 1% a year after 30 — but when they drop too low, the effects can quietly build up and be easy to blame on stress or simply "getting older".
Here are the signs worth paying attention to, and how a simple blood test can tell you whether low testosterone is actually the cause.
The common signs of low testosterone
No single symptom confirms low testosterone, but a cluster of the following is a good reason to get checked:
- Low sex drive and reduced spontaneous erections
- Persistent fatigue and low energy, even after rest
- Low mood, irritability or difficulty concentrating ("brain fog")
- Loss of muscle and strength, or increased body fat around the middle
- Poor recovery after exercise
- Reduced motivation and general drive
- Less commonly, hot flushes, thinning body hair or breast tenderness
What causes it?
Testosterone can fall for several reasons: natural ageing, being overweight, type 2 diabetes, excessive alcohol, chronic stress and poor sleep, some medications, and less often a problem with the testes or the pituitary gland in the brain. Identifying the cause changes how it's managed — which is another reason bloods are the sensible first step.
How is it tested?
Testosterone is measured with a simple blood sample, ideally taken in the morning (before 11am) when levels peak. Because a lot of testosterone is bound to a protein called SHBG, the most useful picture comes from measuring both total testosterone and free (active) testosterone. If a first result is borderline, it's usually repeated to confirm.
Check your testosterone
Total and free testosterone give the clearest read on whether levels are genuinely low. Add SHBG and LH/FSH for a fuller hormonal picture.
Book a testosterone testWhat can you do about it?
If levels are low, the first-line steps are often lifestyle: losing excess weight, improving sleep, reducing alcohol, and building resistance exercise into your week can all raise natural levels. Where a genuine deficiency is confirmed and symptoms persist, a doctor may discuss testosterone replacement therapy (TRT) — but only after appropriate testing and a conversation about the risks and benefits.
When to get checked
If you recognise several of the signs above — particularly low libido, fatigue and low mood together — it's worth a test rather than guessing. Knowing your numbers takes the uncertainty out of it and gives you and your doctor a clear starting point.
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Specialist interest: Cardiovascular Medicine · OneMedicine, CQC-registered clinic