Low testosterone is diagnosed from a combination of relevant symptoms and consistently low hormone measurements. A single result or fatigue alone is not enough to establish the diagnosis.[1]
Symptoms provide the reason for testing
Changes in sexual interest, erection difficulties, reduced muscle strength, and other symptoms may lead to testing. These symptoms can also have other explanations, so the history matters.[2]
Describe what changed and when, including medicines, illness, sleep, and reproductive goals.
Timing and repeat testing matter
The Endocrine Society recommends confirming a low result with another morning fasting total-testosterone measurement. It also emphasizes accurate assays and appropriate reference ranges.[1]
The instructions for collection should come from the clinician or laboratory. Keeping the collection time and original report makes comparison easier.
A result near a boundary may require a more detailed interpretation rather than being treated as a simple pass or fail.
Total and free testosterone can add different information
Most testosterone circulates bound to proteins. Total testosterone includes bound and unbound hormone; free testosterone describes the unbound portion. The guideline recommends considering free testosterone when indicated, rather than using it as a universal replacement for total testing.[1][2]
Diagnosis is followed by a cause assessment
When deficiency is confirmed, further evaluation can help distinguish a problem involving the testes from one involving the pituitary or hypothalamus. Other hormones and clinical findings may contribute.[1]
Symptoms that continue with reassuring testosterone results still deserve an explanation. The review can return to sleep, medicines, mood, and other possible contributors rather than treating testosterone as the only available answer.
