You still train as hard as last year, but the progress is gone, your libido is dormant, and around half past two you almost fall asleep at your desk. "Low testosterone" is then a tempting explanation. Sometimes it fits, often it is something else. The difference sits in your blood values.
Honestly: symptoms alone are a poor guide. They point you in a direction, but never to a diagnosis.
What are the symptoms of low testosterone?
The most common signals are ongoing fatigue, lower sex drive, erection problems, stalling muscle gains, more belly fat, a shorter fuse and poor concentration. What stands out: no single symptom is specific to testosterone. You see exactly the same complaints with poor sleep, a slow thyroid, an iron deficiency or prolonged stress.
That is why it is so risky to conclude on feel that your testosterone is low. You could spend months working on the wrong problem.
Which blood values go with which symptom?
Use the table below as a starting point. Per complaint you see which value you mainly want to measure, and which common alternative cause you should not forget.
| Symptom | Measure first | Do not forget to rule out |
|---|---|---|
| Ongoing fatigue | Total testosterone + free testosterone | Ferritin, TSH |
| Reduced libido | Free testosterone | Prolactin, estradiol |
| Stalling muscle gains | Total testosterone | Vitamin D, sleep and recovery |
| Low mood, short fuse | Total testosterone | TSH, vitamin B12 |
A low total alongside a high LH usually points to a problem in the testes themselves. A low total with a low or normal LH points more to signalling from the brain. That distinction shapes the next step, and belongs with your doctor.
Why your free fraction often tells you more
Many men are told their total testosterone is "normal", while the complaints persist. The explanation often sits in the free fraction. Your tissues do not use your total, but mainly your free testosterone. If the protein SHBG binds a large part of your testosterone, less active hormone remains, even though your total looks fine.
That is why measuring only total testosterone with persistent complaints is a half measure. The full explanation of this difference is in free testosterone and SHBG. The core: a single number never definitively rules out a problem.
What can cause low testosterone?
A lowered testosterone is usually not a standalone problem, but a consequence of something else. The best-known causes in active men:
- Sleep loss: chronically short sleep noticeably depresses your testosterone.
- Excess weight: fat tissue converts testosterone into estradiol through aromatase, shifting the balance.
- Chronic stress: prolonged high cortisol levels often coincide with lower testosterone.
- Too much alcohol: regular heavy drinking disrupts your hormone balance.
- Overtraining: training too hard without enough recovery can temporarily lower your value.
The Netherlands Nutrition Centre (Voedingscentrum) stresses that a healthy weight and a varied diet form the foundation. In other words: before you think of therapy, there is often gain to be had from your lifestyle.
How do you know your value is really low?
The Dutch College of General Practitioners (NHG) stresses that you do not establish low testosterone on a single measurement. Draw in the morning, preferably fasted, and repeat a deviating result on another day. Only when a lowered value coincides with matching complaints does the story become clinically interesting.
The Endocrine Society advises in its guideline only to speak of low testosterone when a lowered value coincides with matching complaints. An isolated number without complaints is rarely a reason to intervene. In other words: your lifestyle and your symptoms together shape the picture, not a single figure.
What do you do with a low result?
Do not jump straight to therapy. Start with the basics: sleep, body composition, resistance training and alcohol. What works and what does not is covered in increasing testosterone naturally. To understand the whole picture, the pillar overview testosterone: symptoms and blood values helps.
You can measure the right values at once with the General Hormones panel. If the result stays low or your complaints persist, discuss this with your GP.
When is therapy on the table?
Sometimes lifestyle is not enough and testosterone therapy comes into view. That is a decision you make together with a doctor, based on repeated measurements and matching complaints, not on a single low number. The Dutch College of General Practitioners (NHG) is cautious here: therapy is not a quick fix and requires monitoring of, for example, your hematocrit and your prostate value.
My stance: see therapy as the last step, not the first. Anyone who first addresses their sleep, weight and alcohol avoids starting a lifelong treatment for a problem that was partly solvable on their own. If you do start therapy, you track your values through the TRT Monitoring panel.
Disclaimer
Every blood test result includes a professional assessment by a BIG-registered doctor. This article gives general information and cannot replace medical advice. Always discuss a deviating result or persistent complaints with your GP.
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