The diagnosis has two halves, and both have to be present. There must be a clinical picture — symptoms or physical findings — and there must be laboratory evidence of low total testosterone on more than one occasion.
Because levels fluctuate and acute illness can push them down temporarily, a low result is usually repeated on a separate morning before anyone treats it. When results are borderline or when a man is obese or has other binding-protein changes, additional testing such as free testosterone may be considered.
If levels are genuinely low, the next question is why. Depending on the situation, that can mean checking pituitary hormones and other labs to distinguish a testicular cause from a pituitary or hypothalamic one. That distinction changes the conversation, particularly for men who want children.
Risks and limitations
- Assays and reference ranges differ between laboratories, so results are interpreted in context.
- Illness, poor sleep, acute stress and some medications can lower a result temporarily.
- A borderline value is not a diagnosis; it is a reason to look more carefully.
- Not every man with low results needs or should start therapy.