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Blood Sciences

Blood Test Information

minimum sample volume required ~ 5ml

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Test Code: COR

Other acceptable tube types
Lithium heparin (pale green)

Special instructions
If performing a short synacthen test, please collect all samples and send together.

Reference range
Please see individual reports for interpretation.


Turnaround Time
2 days

Department: Biochemistry

Clinical Application
Measurement of cortisol is most useful as part of a dynamic function test. Low random cortisols (especially from around 9am) may indicate cortisol deficiency: if this is suspected a short synacthen test should be performed (the test has no place in assessment of suspected Cushing's syndrome). Measurement of random cortisol is unhelpful in the investigation of suspected Cushing's syndrome, where either a 24-hour urine free cortisol measurement or an overnight dexamethasone suppression test should be used. Serial cortisol measurements are used to check adequacy of cortisol replacement therapy ("cortisl day curves"). Test limitations: Prednisolone, methylprednisolone or prednisone may cause falsely elevated cortisol results.


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