Insulin-to-C-Peptide Ratio

Sample type

Serum (Red-top tube or gel-barrier tube)

Uses

To differentiate insulinoma from factitious hypoglycemia due to insulin

Precautions

You will probably need to fast (not eat or drink) for 8–12 hours before the test.

Interfering factors

There are ethnic differences in insulin/C-peptide ratio in both fasting and glucose-stimulated conditions in normal young nondiabetic pregnant women. Compared with their Caucasian and Hispanic counterparts, African American women had indices suggestive of lower insulin production and greater insulin resistance (i.e., a lower C-peptide concentration, a lower C/I ratio, and elevations in insulin and the I/G ratio).

Pre-analytical errors

• Specimen not serum

• hemolyzed specimen

The corrective action

The sample must be rejected and another sample be obtained.

Post-analytical errors

1- reports were sent to the incorrect patient

2- write the wrong name in the report or the wrong results.

3-incorrect calculation

The corrective action

1-communication with patient, apologising for the error, and providing him with the correct report

2-If the report is not delivered to the patient and this error is discovered, the correct result or the correct name must be written, but if the report is delivered to the patient, you must communicate with him, apologise to him, and tell him that an error has occurred and replace it with the correct report.

3-should read pamphlet carful then perform calculation

it is better perform calculation more than once to be sure we have correct calculation

Reference range

fasting molar ratio insulin to C-peptide = 1.0