Home
HelpTest Code INSFT Insulin, Free and Total, Serum
Useful For
Assessing free (bioactive) insulin concentrations in patients with known or suspected anti-insulin antibodies
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| INSF | Insulin, Free, S | No | Yes |
| INSTO | Insulin, Total, S | Yes, (Order as INS) | Yes |
Method Name
Electrochemiluminescence Immunoassay (ECLIA)
Reporting Name
Insulin, Free and Total, SSpecimen Type
SerumSpecimen Required
Patient Preparation:
1. Fasting (8 hours)
2. For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 2.45 mL
Collection Instructions:
1. Avoid hemolysis
2. Label specimens with corresponding collection times.
3. Serum-gel tubes should be centrifuged within 2 hours of collection.
4. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.
5. Send specimen refrigerated
Additional Information: If multiple specimens are collected, send separate order for each specimen.
Specimen Minimum Volume
0.75 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 14 days | |
| Frozen | 180 days | ||
| Ambient | 24 hours |
Reference Values
FREE INSULIN:
3-25 mcIU/mL
TOTAL INSULIN:
3-25 mcIU/mL
Interpretation
Free insulin represents the portion of total insulin unbound by anti-insulin antibodies in the circulation. This fraction serves as a measure of biologically active insulin and provides an indication of the true relationship between insulin and blood glucose.
Most individuals do not have anti-insulin antibodies in circulation and therefore the free and total insulin concentrations would be equivalent.
When a significant difference between total and free insulin Concentrations is observed following ultrafiltration, the result is suggestive of the presence of insulin antibodies. In these cases, confirmation of the presence of anti-insulin antibodies (Mayo Test ID: INAB) may be helpful.
Clinical Reference
1. Lupsa BC, Chong AY, Cochran EK, Soos MA, Semple RK, Gorden P. Autoimmune forms of hypoglycemia. Medicine (Baltimore). 2009;88(3):141-153
2. Sapin R, Le Galudec V, Gasser F, Pinget M, Grucker D. Elecsys insulin assay: free insulin determination and the absence of cross-reactivity with insulin lispro. Clin Chem. 2001;47(3):602-605
3. Sacks DB: Diabetes mellitus. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics 6th ed. Elsevier; 2018:1160-1200
Day(s) Performed
Monday, Wednesday, Friday
Report Available
1 to 4 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
83527-Free Insulin
83525-Total Insulin
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| INSFT | Insulin, Free and Total, S | 48615-9 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| INSTO | Insulin, Total, S | 20448-7 |
| INSF | Insulin, Free, S | 6901-3 |