Investigation : Cortisol
Specimen type : Serum
Spec container : Serum Gel 
Volume required : 5 ml
Turnaround : <48 hours

Reference RangeUnits
06:00h-10:00h 133 - 537nmol/l
24:00h <50

From 27/10/15 the cortisol results will be approximately 20% lower

Cortisol increases in pregnancy, with oral contraception and in stress.

A Synacthen Test (SST) is unnecessary if a 9:00 h or random cortisol level is > 400 nmol/L.

Take a blood specimen for cortisol at around 9:00 h and send to the lab with the form marked -"Emergency - pre-Synacthen sample", also telephone extension 4230 or 4755 to inform the Duty Biochemist that you are sending a pre-Synacthen cortisol, giving the patientís name and your Bleep number. The baseline cortisol result will be phoned within 2 h.

Cortisol < 400 nmol/L: Give 250 µg Synacthen intramuscularly and take serum cortisol specimens at 30 and 60 mins post Synacthen. Send both blood specimens together to the laboratory, clearly identified with times of specimens and patientís details..


Cortisol >450 nmol/L at 30 minutes indicates adequate adrenal reserve.
Cortisol <450 nmol/L at 30 minutes indicates inadequate adrenal reserve.

If the increase in cortisol is not achieved until the 60 mins this is a blunted response and is most commonly seen in patients on long term steroids. This can also be seen in hypopituitarism. Contact the Duty Biochemist for further advice if required on 4755 or 4230.

Additional information on cortisol and its clinical use can be found here: cortisol.

New cortisol reference interval 01/05/21, results unaffected.

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