Preferred Sample Type


Suitable Specimen Types

  • Serum
  • EDTA Plasma
  • Li Hep Plasma
Minimum sample volume 200 uL blood (1 x paed Lith Hep tube)

Sample Processing in Laboratory


Sample Preparation


Turnaround Time

1 day

Sample Stability

Store at 4 ºC for up to five days. For longer periods store at -20 ºC.


General Information

Cortisol is the most significant glucocorticosteroid and is essential for the maintenance of several body functions. Like other glucocorticosteroids it is synthesised in the zona fasciculata of the cortex of the Adrenal gland. Cortisol is secreted in response to adrenocorticotrophic hormone (ACTH) which is released from the anterior pituitary gland. Cortisol is bound to cortisol-binding globulin and albumin with only the free (unbound) fraction being biologically active

Blood and urine tests for cortisol may be used to help diagnose Cushing’s syndrome and Addison’s disease, two serious disorders affecting the production of cortisol by the adrenal gland. Cushing's syndrome is caused prolonged exposure to elevated levels of either endogenous glucocorticoids or exogenous glucocorticoids, while Addison's disease is caused by damage to the adrenal, and is associated with too little cortisol. However, a single random cortisol measurement is of limited diagnostic value. Therefore, if cortisol concentrations are abnormal, additional testing may be required to confirm the diagnosis and decide on treatment.

These may include a dexamethasone suppression test or 24 hour urinary cortisol in the diagnosis of Cushing's syndrome, or a short synacthen test (SST) for the diagnosis of Addison's disease/adrenal insufficiency.

Patient Preparation

The collection time should be noted on the request form.

Samples from patients receiving high biotin doses (i.e. >5 mg/day) should be taken at least 8 hours post dose.

Pregnancy, contraceptives and oestrogen therapy give rise to elevated cortisol concentrations.

Samples from patients treated with prednisolone, methyl-prednisolone or prednisone may give falsely elevated concentrations of cortisol. Therefore, if your patient is taking these mediciations please order a Prednisone Test.


Samples should be clot-free and free of red cells or other particulate matter. The presence of fibrin may cause erroneous results.

Reference Range

Before 10 am: 101.2 - 535.7 nmol/L,

After 5 pm: 79 - 477.8 nmol/L,

(Source: Abbott Diagnostics)


  • EQA Scheme?: Yes
  • EQA Status:


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Protection of Personal Information – Laboratory Medicine comply with the Trust Data Protection Policy and have procedures in place to allow the Directorate and it’s employees to comply with the Data Protection Act 1998 and associated best practice and guidance.

The Trust Laboratories at Heartlands Hospital, Good Hope Hospital and Solihull Hospital were awarded UKAS (United Kingdom Accreditation Service) accreditation to the internationally recognised ISO 15189 standard in May 2015. For a list of accredited tests and other information please visit the test database
Tests not appearing on this scope are either under consideration or in the process of accreditation and so currently remain outside of our scope of accreditation. However, these tests have been validated to the same high standard as accredited tests and are performed by the same trained and competent staff.

For further information contact Louise Fallon, Quality Manager, 0121 424 1235