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Beaumont Laboratory

Insulin, Free

Free Insulin, MAYO: INSFT, EPIC: LAB6269, SOFT: XINS1


The patient should be fasting (8 hours) prior to specimen collection.

Specimen Collection Criteria

Collect (preferred specimen): One plain Red-top tube.
Also acceptable: One Gold-top SST tube.

Send specimen for processing immediately after collection.

Physician Office/Drawsite Specimen Preparation

Let specimen clot 30-60 minutes and centrifuge to separate serum from cells within 2 hours of collection. Transport serum to a plastic transport tube and freeze (-20°C/-4°F or below).

Preparation for Courier Transport

Transport: 1.0 mL serum, frozen (-20°C/-4°F or below). (Min: 0.5 mL)

Rejection Criteria

  • Hemolyzed specimens.
  • Specimens not collected and processed as indicated.


Specimen Stability for Testing:

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): 180 days

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Sendout Laboratory with any questions.


Sent to Mayo Medical Laboratories, Rochester, MN.


Monday - Saturday.
Results available in 2-4 days.

Reference Range

Free: 2.6-24.9 micro IU/mL
Total: 2.6-24.9 micro IU/mL.

Test Methodology

Electrochemiluminescence Immunoassay.

Clinical Utility

Patients who have been injecting non human insulin for treatment of insulin-dependant diabetes may develop insulin autoantibodies. These antibodies bind directly to insulin making it unavailable for metabolic activity. Free insulin levels can be useful in management of diabetes mellitus patients with known insulin autoantibodies.

CPT Code

83527, 83525.

Test Codes


Last Updated


Microtainer® and Vacutainer® are registered trademarks of Becton, Dickinson and Company.
UroVysion® is a registered trademark of Abbott Laboratories. ThinPrep® is a registered trademark of Hologic, Incorporated.

This directory currently reflects information only for specimens collected and/or processed at the Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.