Cortisol
Cortisol should ideally be measured between 08:00 and 09:00, when levels are normally at their highest.
Cortisol testing does not need to be scheduled around a particular menstrual-cycle day, including where cycles are irregular.
For repeat testing, samples should be collected at approximately the same time of day to allow meaningful comparison.
Testosterone
For assessment of testosterone status, blood samples should preferably be collected in the morning, ideally before 11:00, when testosterone concentrations are generally at their highest.
Where possible, testing should be performed fasted and when the patient is clinically well. A low or borderline testosterone result should generally be confirmed with a second morning measurement before a diagnosis of testosterone deficiency is established.
For patients receiving testosterone replacement therapy, the timing of blood sampling relative to testosterone administration is important. Please seek advice from your prescribing clinician regarding the appropriate timing of the blood test.
For all testosterone monitoring, the following should be recorded:
Date and time of blood collection
Date and time of the most recent testosterone administration
Testosterone dose administered
Route/formulation of testosterone, where relevant
