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Insulin Level

Insulin

Test Codes

EPIC: LAB5811, INSUL, Antrim: 15548

Department

Chemistry

Instructions

The patient should fast overnight prior to specimen collection.

Specimen Collection Criteria

Collect: One Gold-top SST tube. (Minimum Whole Blood: 2.0 mL)

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Transfer serum to a plastic aliquot tube and refrigerate (2-8°C or 36-46°F) immediately. (Minimum Serum: 0.5 mL)

Preparation for Courier Transport

Transport: Serum aliquot tube, refrigerated (2-8°C or 36-46°F). (Minimum Serum: 0.5 mL)

Rejection Criteria

• Lipemic, icteric, or grossly hemolyzed specimens.
• Samples left on the clot at room temperature.
• Samples subjected to repeated freeze/thaw cycles.

In-Lab Processing

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Transfer serum to a plastic aliquot tube and refrigerate (2-8°C or 36-46°F) immediately. (Minimum Serum: 0.5 mL)

Storage

Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers^® with Separator Gels
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers^® without Separator Gels
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Dearborn Chemistry Laboratory
Royal Oak Automated Chemistry Laboratory

Performed

Monday – Friday.
Results available in 2 business days.

Reference Range

Fasting:                        < 26 mcU/mL 

2hr. Post Glucola:      22 – 71 mcU/mL 

Test Methodology

Chemiluminescent Immunoassay.

Interpretation

Individuals who are significantly overweight have fasting insulin levels that are somewhat higher than those for adults of normal weight.

Patients undergoing insulin therapy may form anti-insulin antibodies that are capable of interfering with this assay.

Insulin levels obtained during a glucose tolerance test appear to have some prognostic value in predicting the benefits of insulin therapy and the likelihood of progression to insulin-dependence and the complications characteristic of diabetes.

Clinical Utility

Insulin assay is used for the quantitative measurement of insulin in serum. This test is used as aid in the diagnosis of insulin-producing neoplasms (islet cell tumor, insulinoma), pancreatic islet cell hyperplasia, to evaluate hypoglycemia, and to evaluate insulin production in diabetes mellitus.

Insulinoma is a rare, islet-cell tumor with insulin hypersecretion. Ninety percent of these tumors are benign. Patients with insulinoma present with hypoglycemia that is the result of the inappropriate secretion of insulin by the tumor. Plasma insulin concentrations decrease progressively in normal fasting patients. Patients with an insulinoma present with high insulin levels and hypoglycemia.

Plasma insulin-to-glucose ratios are also purportedly useful to diagnose insulinoma (1). There are two alternatives. The simple ratio is defined as:

Plasma insulin (microIU/mL)

Plasma glucose (mg/dL)

A simple ratio greater than 0.3 suggests insulinoma.

The "amended" ratio is defined as:

Plasma insulin (microIU/mL)	X 100
Plasma glucose (mg/dL) - 30

An amended ratio greater than 50 suggests insulinoma.

Reference

1. Fajans SS, Floyd JC. Fasting hypoglycemia in adults. N Eng J Med 1976;294;766.

CPT Codes

83525
LOINC: 20448-7

Contacts

Last Updated

10/10/2023