Pathology Handbook


Clinical Indications

Differential diagnosis of documented spontaneous hypoglycaemia.  The measurement of both insulin and C-peptide is undertaken since in some cases of insulinoma, insulin levels may be low whereas C-peptide is almost always unequivocally raised.  Both measurements are required for the identification of factitious insulin observation.
The use of insulin and C-peptide levels to assess endogenous insulin production in Type 2 diabetics is unreliable and should be restricted to patients awaiting renal/pancreatic transplant.

Request Form

Request on ICE


Analysed by referral laboratory if specific criteria met.

Specific Criteria

Differential diagnosis of documented spontaneous hypoglycaemia. Samples will not normally be analysed unless simultaneous glucose analysis shows hypoglycaemia (< 2.5 mmol/L by laboratory assay).
Assessment of endogenous insulin production for patients awaiting renal/pancreatic transplant

Patient Preparation

For investigation of hypoglycaemia, a grey top (fluoride) sample must be taken simultaneously.
For assessment of endogenous insulin production: exogenous insulin suppresses endogenous insulin production. Suggested procedure is to withhold usual pre-meal insulin, give light meal and collect samples after 30 mins. Usual insulin dose can then be given.

Turnaround Time

2 weeks


SST serum AND glucose sample


2 ml


Vacutainer gold top

Vacutainer grey top


Samples must be transported to laboratory immediately.

Patients MUST be bled at Southend hospital

Lab Handling

Sent to referral laboratory (Royal Surrey County Hospital)

Causes for Rejection

Not meeting specific criteria for analysis; delay in sample reaching laboratory; unlabelled or incorrectly labelled sample 

Reference Range

An interpretation of results will be provided on the report.