Cortisol

Measures an adrenal hormone whose level changes over the course of the day.

To assess adrenal function and the daily (circadian) rhythm of cortisol.

1. Check in advance whether the time of day, the day of your menstrual cycle or other timing matters.
2. Cortisol must be drawn at the time specified in the order (often morning, sometimes evening). Tell your doctor about steroid medicines and any current stress.
3. Tell your doctor about hormone preparations and dietary supplements; do not change your treatment on your own.
4. Stay calm before the blood draw and keep to the time agreed with you.

There is no single rule. Whether you need to fast, and for how long, depends on the purpose of the test and the laboratory method; check in advance.

The time of the blood draw is critical: a morning or evening sample, or a special function test, may be needed. The time should be recorded on the report.

• Time of blood draw
• Glucocorticoids and other medications
• Acute stress and illness

Venous blood — serum or plasma, depending on the method

The blood sample is collected by a qualified staff member. The tube type, required volume, and processing and storage conditions are set by the laboratory's specific method. You do not need to store the sample yourself.

What a cortisol result means depends on the time of the blood draw and the type of test; a single high or low result is not a diagnosis.

If your result is outside the reference interval, you have symptoms, or your condition changes, contact your doctor. If symptoms are severe or develop quickly, seek emergency care.

Morning and evening cortisol have different meanings; the collection time should be recorded on the report.