Sign in →

Test ID: INS Insulin, Serum

Reporting Name

Insulin, S

Useful For

Diagnosing insulinoma, when used in conjunction with proinsulin and C-peptide measurements


Management of diabetes mellitus

Clinical Information

Insulin is a hormone produced by the beta cells of the pancreas. It regulates the uptake and utilization of glucose and is also involved in protein synthesis and triglyceride storage.


Type 1 diabetes (insulin-dependent diabetes) is caused by insulin deficiency due to destruction of insulin-producing pancreatic islet (beta) cells. Type 2 diabetes (noninsulin-dependent diabetes) is characterized by resistance to the action of insulin (insulin resistance).


Insulin levels may be increased in patients with pancreatic beta cell tumors (insulinoma).


During prolonged fasting, when the patient's glucose level is reduced to <40 mg/dL, an elevated insulin level plus elevated levels of proinsulin and C-peptide suggest insulinoma.


Insulin levels generally decline in patients with type 1 diabetes mellitus.


In the early stage of type 2 diabetes, insulin levels are either normal or elevated. In the late stage of type 2 diabetes, insulin levels decline.


In normal individuals, insulin levels parallel blood glucose levels.


To compare insulin and C-peptide concentrations (ie, insulin to C-peptide ratio):

-Convert insulin to pmol/L: insulin concentration in mcIU/mL x 6.945 = insulin concentration in pmol/L.

-Convert C-peptide to pmol/L: C-peptide concentration in ng/mL x 331 = C-peptide concentration in pmol/L.

Report Available

1 to 3 days

Day(s) Performed

Monday through Friday

Clinical Reference

1. Threatte GA, Henry JB: Carbohydrates. In: Henry JB, ed. Clinical Diagnosis and Management by Laboratory Methods. 19th ed. WB Saunders Company; 1996:194-207

2. 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

Method Name

Electrochemiluminescence Immunoassay (ECLIA)

Specimen Type


Ordering Guidance

Patients on insulin therapy may develop anti-insulin antibodies. These antibodies may interfere in the assay system, causing inaccurate results. In such individuals, measurement of free insulin INSFT / Insulin, Free and Total, Serum should be performed.

Specimen Required

Patient Preparation:

1. Patient should be fasting.

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.

Supplies: Sarstedt 5 mL Aliquot Tube (T914)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Avoid hemolysis

2. Label specimens with corresponding collection times.

3. Centrifuge and aliquot serum into plastic vial within 2 hours of collection.

Additional Information: If multiple specimens are drawn, send separate order for each specimen.

Specimen Minimum Volume

0.75 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Frozen (preferred) 180 days
  Refrigerated  7 days

Reference Values

2.6-24.9 mcIU/mL


For SI unit Reference Values, see

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
INS Insulin, S 27873-9


Result ID Test Result Name Result LOINC Value
INS Insulin, S 27873-9


If not ordering electronically, complete, print, and send General Request (T239)

Mayo Clinic Laboratories | Endocrinology Catalog Additional Information: