Insulin, produced by pancreatic beta cells, regulates glucose uptake and utilization and is involved in protein synthesis and triglyceride storage. It is often measured alongside C-peptide.
Clinical uses of insulin measurements:
1. Evaluation of possible insulinoma: In cases of hypoglycaemia, diagnosis of insulinoma relies on proving inappropriate secretion of insulin during a hypoglycaemic episode.
2. Hypoglycaemia of infancy due to hyperinsulinaemia.
3. Diagnosis of factitious hypoglycaemia together with measurement of C-peptide.
4. Discrimination of type 1 and type 2 diabetes mellitus: Insulin and C-peptide concentrations are generally low in patients with type 1 diabetes mellitus, and either normal or elevated in early type 2 diabetes, and decreased in later stages.
Sample Requirements and Reference Ranges
|Precautions||Collect after overnight fast or during symptomatic hypoglycaemia, together with glucose sample. Separate and freeze plasma. Transport frozen. Haemolysed specimens unsuitable. For hypoglycaemic screen, only measure when hypoglycaemic (glucose <2.6 mmol/L).|
|Minimum volume||2 mL|
Fasting Insulin: Not applicable
|Turnaround time||7 days|