Indications

Establishment of correct hydrocortisone dose and timing of dose in patients with primary or secondary adrenal insufficiency

Contraindications

None

Procedure

Non-fasting but do not take morning hydrocortisone dose prior to first blood sample.

Record hydrocortisone doses and time of ingestion on sampling sheet.

1. Take blood for cortisol at time 0 then take morning hydrocortisone dose.
2. Take blood for cortisol at 1 and 3hrs, then take lunchtime dose of hydrocortisone (if applicable).
3. Take blood for cortisol at 5 and 8hrs, then take evening dose of hydrocortisone.
4. Take blood for cortisol at 11hrs.

Interpretation guidelines

Serum cortisol at time 0 should be <70nmol/L.
Serum cortisol the rest of the time should be between 200-500nmol/L.

Notes

1. Oestrogen therapy should be stopped 6 weeks before the test, as increased cortisol binding globulin leading to higher cortisol values will make the test difficult to interpret.
2. This test is only valid for hydrocortisone replacement. Prednisolone or Dexamethasone replacement can only be monitored clinically.

Time of blood sampling for serum cortisol

0h	0900h - THEN GIVE MORNING HYDROCORTISONE DOSE
1h	1000h
3h	1200h - THEN GIVE LUNCHTIME HYDROCORTISONE DOSE
5h	1400h
8h	1700h - THEN GIVE EVENING HYDROCORTISONE DOSE
11h	2000h