Cortisol

Specimen requirements

Sample type: Serum (Serum)

Collection requirements: No special requirements

Cost

Price on application

Turnaround time

Please see Turnaround times

Analytical method

Immunoassay

Analysis undertaken at these site(s)

• John Radcliffe 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.