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

Combined Pathology Blood form (Yellow/Black)

Availability

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

Specimen

Serum

Volume

2 ml

Container

Red top (plain) tube or orange top (heparin) for paediatrics

Collection

Samples must be transported to laboratory immediately.

Lab. Handling

Separate immediately into 2 aliquots and freeze at minus 20’C. (IN / CPEP & send; NOIN & save)

Causes for Rejection

Not meeting specific criteria for analysis. Delay in sample reaching laboratory. 

Reference Range