Insulin, Fasting
Also known as: INSULIN FT
Use
The Insulin, Fasting test is primarily used to aid in the detection of insulinoma. Insulinomas are pancreatic neuroendocrine tumors that often result in excessive insulin production, leading to hypoglycemia. However, this test should not be used for diagnosing diabetes mellitus as it specifically measures fasting insulin levels to assist in identifying abnormal insulin production, which can indicate the presence of such tumors.
Special Instructions
Patients should have their specimen collected in a serum separator tube. It is important to ensure that the specimen clots completely at room temperature and that the serum is separated from cells as soon as possible or within two hours of collection. Then, transfer 1 mL of serum to an ARUP Standard Transport Tube. The collected specimen should be stored frozen for optimal stability.
Limitations
The Insulin, Fasting test has specific cross-reactivity characteristics; it reacts on a nearly equimolar basis with insulin analogs such as insulin aspart, insulin glargine, and insulin lispro. Insulin detemir shows approximately 50 percent cross-reactivity, whereas insulin glulisine exhibits negligible cross-reactivity (<3 percent). This must be taken into account when interpreting results, particularly if the patient is on any of these analogs. Additionally, specimens collected in heparinized plasma or in gray (sodium fluoride/potassium oxalate) tubes, vitreous or intravenous fluids, or hemolyzed specimens are unacceptable and can lead to inaccurate results.
FDA ApprovedNew York Approved
Methodology
Immunoassay (CLIA)
Biomarkers
LOINC Codes
- 27873-9
- 27873-9
Result Turnaround Time
1 day
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.4 mL
Container
ARUP Standard Transport Tube
Collection Instructions
Collect using a serum separator tube. Allow the specimen to clot at room temperature, separate serum from cells within 2 hours, and transfer to a transport tube.
Storage Instructions
Store the specimen frozen for stability purposes.
Causes for Rejection
Heparinized plasma, vitreous or intravenous fluids, gray tubes, and hemolyzed specimens are causes for rejection.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 8 hours |
| Refrigerated | 1 week |
| Frozen | 1 month |