Skip to main content
Oxford University Hospitals NHS Foundation Trust
Clinical Biochemistry

Alert Coronavirus / COVID-19

If you have a new continuous cough, a high temperature, or a loss or change to your sense of taste or smell, do not come to our hospitals. Follow the national advice on coronavirus (COVID-19).

Please find information on our services and visiting restrictions in our COVID-19 section.

Patients and visitors must wear a face covering in our hospitals.

This site is best viewed with a modern browser. You appear to be using an old version of Internet Explorer.


Specimen requirements

Sample type: Serum (Serum)

Collection requirements: No special requirements


Price on application

Turnaround time

Please see Turnaround times

Analytical method


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.