Cortisol
The preferred window is 08:00–09:00, when Cortisol is normally near its daily peak. Repeat measurements should be taken at approximately the same time.
Cortisol sampling does not need to be arranged for a particular menstrual-cycle day, including where cycles are irregular. The actual sample time should be recorded. A morning result is not a complete measure of chronic stress or daily cortisol production.
Testosterone
For assessment of natural testosterone status, collect in the morning, ideally before 11:00, when concentrations are generally highest. Where possible, test fasted and when clinically well.
A low or borderline result generally needs a second morning measurement before Testosterone Deficiency is established. Symptoms, medical history and other possible causes still need assessment.
If you are receiving Testosterone Replacement Therapy, timing relative to administration is important. Ask the prescribing clinician which interval is appropriate for your formulation and treatment plan. A generic instruction to test in the morning does not replace that advice.
Record the date and time of collection, the date and time of the most recent testosterone dose, the dose administered and the route or formulation where relevant.