How to Measure Testosterone
Initial Test
- Morning fasting total testosterone — drawn between 8–10 AM
- Ideally measured by LC-MS/MS (liquid chromatography-tandem mass spectrometry) in a certified lab
- Do not test during acute illness — transient functional secondary hypogonadism can occur and confound results
If Low or Borderline
- Repeat at least once (preferably twice) before making a diagnosis
- A single low value is not sufficient to diagnose hypogonadism
If Confirmed Low — Next Step
Measure LH and FSH to distinguish the cause:
| Result | Interpretation |
|---|---|
| LH/FSH high | Primary hypogonadism (testicular failure) |
| LH/FSH normal or low | Secondary hypogonadism (hypothalamic-pituitary dysfunction) |
Source: UpToDate — Clinical features and diagnosis of male hypogonadism
Related notes: