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Insulin – Clotted serum sample |
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| Room temp | 4°C | -20°C or below | |
| Separated/centrifuged | 2 hours | 5 days | Stable |
| On cells | 2 hours | 5 days | N/A |
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Insulin – EDTA sample |
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| Room temp | 4°C | -20°C or below | |
| Separated/centrifuged | 5 days | 5 days | Stable |
| On cells | 5 days | 5 days | N/A |
Insulin key messages:
Please note our preferred sample type is separated EDTA plasma rather than whole blood. EDTA plasma samples for insulin analysis can be sent at room temperature to be received within 5 days of sample collection.
Haemolysis hugely impacts insulin stability (decrease in measured insulin), however in some circumstances we can report a useful qualitative result in haemolysed samples i.e. inappropriately raised insulin in hypoglycaemia.
Clotted samples that have been stored at 4 °C are stable for up to 5 days for insulin analysis, whether separated or not.
All samples must be accompanied by a sample for glucose taken at the same time (fluoride oxalate tube)
This should be below 2.8 mmol/L, otherwise the assay will not be performed.
Insulin can be measured to assess extreme insulin resistance upon discussion with the laboratory.
pmol/L
17.8 – 173
Insulin is a hormone secreted by the islet cells of the pancreas that regulates carbohydrate metabolism. Measurement of plasma insulin levels is helpful in the diagnosis of insulinoma. Eighty percent of patients have a single benign tumor, usually < 2-cm in diameter, located about equally in the head, body or tail of the pancreas. About 10% of patients have multiple tumors associated with multiple endocrine neoplasia type 1 and the remaining 10% have metastatic malignant insulinoma.
Patients with insulinomas usually present with fasting hypoglycaemia, but occasionally may present with postprandial hypoglycaemia. The diagnosis depends on demonstrating elevated serum insulin and C-peptide levels when the patient has symptoms of hypoglycaemia and plasma glucose is low. One third of patients with insulinoma have an insulin level within the normal range, so it must be shown that the insulin level is high for the patient’s glucose level. Inappropriate elevation of insulin can occur in two conditions; insulinoma and exogenous administration of insulin. This distinction can be made by measuring C-peptide, which is created by the cleavage of proinsulin to insulin within the beta cell. It is not present in pharmaceutical insulin. Serum C-peptide level is low with surreptitious injection of insulin and increased with insulinoma.
Insulin antibodies in diabetic patients who have been treated with beef or pork insulin may interfere with insulin quantitation. A test for insulin antibody should be included in the work-up of these patients.
Insulin levels are increased in obesity, Cushing’s syndrome, and acromegaly. Patients taking oral contraceptives, exogenous corticosteroids, or L-dopa have elevated insulin levels.
7 days
In house
Local assay
We welcome referrals for insulin. If you are a new requestor please complete the following form: Generic New Requestor Form
We now also have the option to use NPEx for referral requesting.
Further information about sample requirements for this test can be found here: Plasma Insulin referred test questionnaire
Further information about sample labelling requirements for this test can be found here: Specimen Labelling Procedure
Specimen Labelling Procedure
8210
