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Alternative names, keywords |
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Samples required |
● Clotted blood (gold cap, 5 mL tube). Smaller tubes are available for paediatric samples. |
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Test indications |
Suspected adrenal dysfunction. For short Synacthen test (SST) and dexamethasone suppression test see dynamic function tests. |
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Factors affecting test performance/ results |
Pregnancy, contraceptives and estrogen therapy give rise to elevated cortisol concentrations. Falsely raised results may occur in samples from patients treated with prednisolone, 6-α-methylprednisolone or prednisone. During metyrapone tests, 11-deoxycortisol levels are elevated; cortisol results may be falsely elevated due to cross reactions. In patients with 21-hydroxylase deficiency, increased 21-deoxycortisol levels can give rise to falsely elevated cortisol results. Samples should not be taken from patients receiving therapy with high biotin doses (i.e. > 5 mg/day) until at least 8 hours following the last biotin administration. In rare cases, interference due to extremely high titres of antibodies to analyte-specific antibodies, streptavidin or ruthenium can occur. Results should always be assessed in conjunction with the patient’s medical history, clinical examination and other findings. |
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Reference range |
Morning hours (6-10 am): 133 - 537 nmol/L * * A 9am cortisol above 275 nmol/L makes adrenal insufficiency unlikely. The time of sample collection must be taken into account when interpreting results due to the cortisol secretion circadian rhythm. Severe stress can also give rise to elevated cortisol levels. |
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Turnaround time |
Same day (within 1h if urgent) |
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Enquiries |
Biochemistry (Automation) |