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Short Synacthen Test (SST)

Clinical Biochemistry

Background Information

The short Synacthen test (SST) is a test of adrenal insufficiency which can be used as a screening procedure in the non-critically ill patient. The test is based on the measurement of serum cortisol before and after an injection of synthetic ACTH (Synacthen).

This test is not recommended if pituitary problems are suspected. An endocrine referral is required in this situation as alternate stimulation tests may be necessary.

When to consider an SST

  • Consider an SST if the patient is suspected to have adrenal insufficiency and assessment has been carried out with a morning cortisol (collected 08:00-09:00) confirming low levels.
  • Do not proceed to an SST without a morning cortisol. The exception to this is patients who have had pituitary surgery or pituitary apoplexy, when a 6 week SST is indicated after initial event.
  • Primary Care - Please discuss with Endocrinology via Advice & Guidance.
  • Secondary Care - Please refer to advice on intranet site (Diabetes & Endocrinology - Guidelines) regarding assessment of steroid insufficiency.
  • Please note: If this test is required in a child, please contact the paediatric endocrine team on ext 8476 to discuss.

Patient Preparation

Refer to Endocrinology/local guidelines as appropriate (see above).

Sample Requirements

If patient on high dose biotin therapy (>5mg/day) collect samples at least 8 hours after the last dose.

For adults, blood taken into 5mL gold top gel tubes (or rust top for the Acute Unit)

5ml gold tube


For children, blood taken into 3.5mL rust top gel tubes

3.5ml rust top tube


For neonates, blood taken into 0.8mL minicollect lithium heparin tubes

Sample tube: pale green cap


Storage/Transport

Send both blood samples to the laboratory at ambient temperature. If unavoidable can be refrigerated overnight.

Required Information

Relevant clinical details including any steroid treatment.

Turnaround Times

The assays are run throughout the day and night.

The in-lab turnaround time is less than 24 hours.

Result Interpretation

A cortisol of >420nmol/L at 30 minutes post Synacthen indicates an adequate adrenal response.

Failure to meet the above criteria indicates probable Addison's disease or very marked adrenal atrophy secondary to prolonged absence of ACTH stimulation. Further tests are required to differentiate between the two, seek endocrine opinion.

A normal response does not exclude ACTH deficiency, which requires an endocrine referral if suspected.

Further Information

To learn more about the short Synacthen test visit Lab Tests Online

Page last updated: 17/03/2026 | Page last reviewed: 17/03/2026

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