At a glance
- Symptoms can have many causes
- Diagnosis generally requires at least two early-morning fasting testosterone tests
- Accurate assays and reference ranges matter
- LH, FSH, history, and additional testing help identify the cause
Start with symptoms and context.
Low libido, erectile changes, reduced spontaneous erections, fatigue, depressed mood, lower muscle mass, anemia, and changes in bone health can occur with testosterone deficiency. They can also occur with sleep disorders, medication effects, thyroid disease, depression, metabolic illness, and many other conditions.
A clinician reviews the timing and pattern of symptoms, medical and fertility history, medication and supplement use, sleep, alcohol or drug exposure, prior injury or treatment, and other health conditions.
Confirm the laboratory pattern.
Current Endocrine Society guidance recommends confirming low testosterone with at least two early-morning, fasting measurements using an accurate assay. Free testosterone may be useful when total testosterone and symptoms do not align or when SHBG is likely to be altered.
A result should be interpreted with the laboratory method, reference range, timing, acute illness, sleep, and medications in mind.
Look for the cause.
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| Test or area | What it adds |
|---|---|
| LH and FSH | Helps distinguish primary testicular from secondary pituitary or hypothalamic patterns |
| Total and free testosterone | Describe measured testosterone exposure in context |
| SHBG | Helps interpret bound and free testosterone |
| Prolactin | May identify a pituitary-related contributor when indicated |
| CBC / hematocrit | Establishes a baseline before therapies that can raise red-blood-cell concentration |
| PSA and prostate assessment | Supports age- and risk-appropriate shared decisions |
| Metabolic and thyroid testing | Looks for common conditions that can overlap with symptoms |