Low Testosterone: Symptoms and How It Is Properly Diagnosed

What is testosterone deficiency?

Testosterone is made in the testes under the control of the brain. It supports desire, erections, muscle, bone, red blood cells, energy and mood. Testosterone deficiency, or male hypogonadism, means the body produces too little testosterone to the point of causing symptoms.

The European Association of Urology (EAU) is clear that diagnosis requires both compatible symptoms and consistently low blood levels. It is not diagnosed from age, tiredness or a single blood result.^[1]

Why the diagnosis must be right

Testosterone testing and prescribing have grown rapidly, partly because advertising suggests that tiredness or a growing waistline means low testosterone. These symptoms are far more often caused by short sleep, stress, depression and excess weight. Accurate diagnosis helps avoid unnecessary treatment.^[1]

Testosterone given to men who are not truly deficient does not reliably make them feel better, but it has definite downsides: suppressed sperm production, smaller testes and thicker blood. At the same time, men who are genuinely deficient deserve proper diagnosis and care.

How common is it with proper criteria?

The European Male Ageing Study (EMAS), published in 2010, studied European men aged 40–79. Using strict criteria, at least three sexual symptoms together with low blood levels, symptomatic late-onset hypogonadism was found in only about 2.1%.^[4] That is far lower than the proportion of men with a low blood result alone.

This shows that a low result is not the same as deficiency requiring treatment, and that testosterone does not fall to disease levels in every older man.

Causes of low testosterone

There are two broad groups of causes.^[1],[2]

• Primary (testicular) problems, such as injury, infection, chemotherapy or radiation, or genetic conditions. LH and FSH are high because the brain is trying to stimulate testes that cannot respond.
• Secondary (brain or pituitary) problems, such as obesity, diabetes, sleep apnoea, long-term opioid or corticosteroid use, previous anabolic steroid use, pituitary tumours or high prolactin. LH is low or inappropriately normal.

Acute illness, fasting and very heavy training can also lower testosterone temporarily, so testing should not be done while you are unwell.

How to get a reliable result

First, symptoms. The more specific ones are reduced sexual desire, fewer morning erections and erectile dysfunction. Fatigue, low mood, poor concentration and loss of muscle are common but non-specific.^[1],[2]

Second, correctly timed blood tests. Testosterone peaks in the morning and falls after meals, so blood should be taken in the morning while fasting, and a low result must be repeated on another day to confirm it.^[1],[2] The Endocrine Society uses the harmonised lower limit of normal of 264 ng/dL, about 9.2 nmol/L.^[2]

Third, finding the cause and reading results carefully. In men whose binding protein (SHBG) may be abnormal, such as those with obesity, diabetes, liver disease or older age, SHBG and calculated free testosterone may be needed. LH and FSH show whether the problem lies in the testes or the brain.^[1],[2]

After the diagnosis

Results should be interpreted with the units, each laboratory's reference range and symptoms together. A value slightly below the threshold in a man without symptoms is very different from a clearly low value with prominent symptoms.^[1],[2]

Before deciding on treatment, reversible factors should be addressed: weight loss, treating sleep apnoea, reviewing medicines that suppress testosterone and controlling chronic illness. In many men, levels improve as overall health improves.^[1]

If deficiency is confirmed and symptoms are clear, testosterone replacement therapy (TRT) is one option. Fertility, risks and a follow-up plan should be discussed in detail before starting. Men who may want children should say so, because alternatives exist that do not suppress sperm production.^[1],[2]

How we care for you at Dr. Kris Clinic

We start by listening to all your symptoms, not just looking at a number, and we look for other causes of tiredness or low desire, such as sleep, stress or depression, in English or Thai.

If hormone testing is needed, we arrange a fasting morning blood test, confirm any low result, and explain the findings with their units. Many men told they have “low T” after a single test find they do not need hormone treatment at all. When treatment is needed, we plan it and its monitoring safely with you.

Frequently asked questions

Dr. Krida Uakridathikarn (Dr. Kris)

Board-certified family physician with certificate training in clinical sexology and sexual medicine. He works at Suratthani Hospital and provides sexual health, hormone and LGBTQ+ inclusive care at Dr. Kris Clinic. Profile and CV

References

1. EAU Guidelines 2026: Male Hypogonadism
2. Endocrine Society: Testosterone Therapy for Hypogonadism (2018)
3. FDA: Testosterone Information; June 2026 labelling update
4. Wu et al. EMAS. N Engl J Med. 2010;363:123–135. doi:10.1056/NEJMoa0911101

Keep reading

Main guide: Men's sexual health

Tests Before Starting Testosterone Therapy (TRT)Testosterone Injections or Gel: How They Differ and How to ChooseTestosterone Enanthate vs Undecanoate: How the Two Injections Differ

This article is general education, not personal medical advice or a promise of results. Diagnosis and treatment require assessment by a doctor. Content reflects the cited sources as of the update date.