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Clinical Biochemistry

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Specimen requirements

Sample type: Serum (Serum)

Collection requirements: No special requirements


Price on application

Turnaround time

Please see Turnaround times

Analytical method

Immunoassay - Indirect / Competitive

Analysis undertaken at these site(s)

  • John Radcliffe Hospital
  • Churchill Hospital
  • Horton General Hospital

Reference intervals

In adult patients who are not on steroid treatment,

- 9 a.m. cortisol <100 nmol/L suggests adrenal insufficiency

- 9 a.m. cortisol >400 nmol/L makes adrenal insufficiency unlikely

- For 9 a.m. cortisol of 100-400, consider a short synacthen test

- Midnight cortisol <50 nmol/L excludes endogenous Cushing's

- 9 a.m. cortisol <50 nmol/L after overnight dexamethasone suppression excludes endogenous Cushing's syndrome. For advice, please consult Endocrinology.

A random (e.g. non-9.00 a.m.) cortisol or a value when patient is on steroids is uninterpretable.

Last reviewed:09 July 2024