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Official Description

C-peptide

© Copyright 2025 American Medical Association. All rights reserved.

Common Language Description

The CPT® Code 84681 refers to the laboratory test for measuring C-peptide levels in the blood or urine. C-peptide is a byproduct of insulin production, and its measurement is crucial for assessing the functionality of pancreatic beta cells, which are responsible for insulin secretion. This test is particularly significant in the context of diabetes management, as it helps to monitor insulin production and can aid in diagnosing the underlying causes of low blood glucose levels. The C-peptide test may be ordered for patients who have recently been diagnosed with diabetes or metabolic syndrome to evaluate their residual beta cell function. Additionally, it is useful in the detection and monitoring of insulinomas, which are tumors that arise in the islet cells of the pancreas and can lead to excessive insulin production. Elevated C-peptide levels may indicate conditions such as endogenous insulin production, insulinomas, hypokalemia, pregnancy, Cushing syndrome, and renal failure. Conversely, low C-peptide levels may suggest diminished beta cell function, which can be a critical factor in the management of diabetes. The test is performed by obtaining a blood sample through venipuncture, which is a separately reportable procedure, or by collecting a 24-hour urine sample. The analysis of serum and urine samples is conducted using a quantitative chemiluminescent immunoassay, a sensitive and specific method for measuring C-peptide concentrations.

© Copyright 2025 Coding Ahead. All rights reserved.

1. Indications

The C-peptide test (CPT® Code 84681) is indicated for several clinical scenarios, particularly in the evaluation of insulin production and pancreatic function. The following conditions may warrant the performance of this test:

  • Monitoring Insulin Production This test is utilized to assess the levels of insulin being produced by the pancreas, which is essential for managing diabetes and understanding the patient's metabolic state.
  • Determining the Cause of Low Blood Glucose Levels The C-peptide test can help identify the underlying reasons for hypoglycemia, which may include excessive insulin production or other metabolic disorders.
  • Evaluating Residual Beta Cell Function In patients newly diagnosed with diabetes or metabolic syndrome, this test helps determine how much insulin the pancreas is still capable of producing.
  • Monitoring Insulinomas The test is also indicated for patients suspected of having insulinomas, as elevated C-peptide levels can indicate the presence of these tumors in the islet cells of the pancreas.

2. Procedure

The procedure for obtaining C-peptide levels involves specific steps to ensure accurate results. The following outlines the procedural steps involved:

  • Step 1: Sample Collection A blood sample is obtained through venipuncture, which is a procedure where a needle is inserted into a vein to draw blood. This step is crucial as it provides the serum needed for the C-peptide measurement. Alternatively, a urine sample may be collected, which should be a 24-hour collection to ensure that the levels of C-peptide are accurately represented over a full day.
  • Step 2: Laboratory Analysis Once the samples are collected, they are sent to a laboratory for analysis. The serum and urine samples are tested using a quantitative chemiluminescent immunoassay. This method is highly sensitive and allows for precise measurement of C-peptide levels, providing valuable information regarding the patient's insulin production and pancreatic function.

3. Post-Procedure

After the C-peptide test is performed, there are generally no specific post-procedure care requirements for the patient. However, it is important for the healthcare provider to review the results in conjunction with the patient's clinical history and other diagnostic tests. Patients may be advised to follow up with their healthcare provider to discuss the implications of the test results, especially if the levels are abnormal, as this may necessitate further evaluation or management of their condition.

Short Descr ASSAY OF C-PEPTIDE
Medium Descr ASSAY OF C-PEPTIDE
Long Descr C-peptide
Status Code Statutory Exclusion (from MPFS, may be paid under other methodologies)
Global Days XXX - Global Concept Does Not Apply
PC/TC Indicator (26, TC) 9 - Not Applicable
Multiple Procedures (51) 9 - Concept does not apply.
Bilateral Surgery (50) 9 - Concept does not apply.
Physician Supervisions 09 - Concept does not apply.
Assistant Surgeon (80, 82) 9 - Concept does not apply.
Co-Surgeons (62) 9 - Concept does not apply.
Team Surgery (66) 9 - Concept does not apply.
Diagnostic Imaging Family 99 - Concept Does Not Apply
CLIA Waived (QW) No
APC Status Indicator Conditionally packaged laboratory tests
Type of Service (TOS) 5 - Diagnostic Laboratory
Berenson-Eggers TOS (BETOS) T1H - Lab tests - other (non-Medicare fee schedule)
MUE 1
CCS Clinical Classification 233 - Laboratory - Chemistry and Hematology
90 Reference (outside) laboratory: when laboratory procedures are performed by a party other than the treating or reporting physician or other qualified health care professional, the procedure may be identified by adding modifier 90 to the usual procedure number.
GA Waiver of liability statement issued as required by payer policy, individual case
Q4 Service for ordering/referring physician qualifies as a service exemption
91 Repeat clinical diagnostic laboratory test: in the course of treatment of the patient, it may be necessary to repeat the same laboratory test on the same day to obtain subsequent (multiple) test results. under these circumstances, the laboratory test performed can be identified by its usual procedure number and the addition of modifier 91. note: this modifier may not be used when tests are rerun to confirm initial results; due to testing problems with specimens or equipment; or for any other reason when a normal, one-time, reportable result is all that is required. this modifier may not be used when other code(s) describe a series of test results (eg, glucose tolerance tests, evocative/suppression testing). this modifier may only be used for laboratory test(s) performed more than once on the same day on the same patient.
26 Professional component: certain procedures are a combination of a physician or other qualified health care professional component and a technical component. when the physician or other qualified health care professional component is reported separately, the service may be identified by adding modifier 26 to the usual procedure number.
59 Distinct procedural service: under certain circumstances, it may be necessary to indicate that a procedure or service was distinct or independent from other non-e/m services performed on the same day. modifier 59 is used to identify procedures/services, other than e/m services, that are not normally reported together, but are appropriate under the circumstances. documentation must support a different session, different procedure or surgery, different site or organ system, separate incision/excision, separate lesion, or separate injury (or area of injury in extensive injuries) not ordinarily encountered or performed on the same day by the same individual. however, when another already established modifier is appropriate it should be used rather than modifier 59. only if no more descriptive modifier is available, and the use of modifier 59 best explains the circumstances, should modifier 59 be used. note: modifier 59 should not be appended to an e/m service. to report a separate and distinct e/m service with a non-e/m service performed on the same date, see modifier 25.
77 Repeat procedure by another physician or other qualified health care professional: it may be necessary to indicate that a basic procedure or service was repeated by another physician or other qualified health care professional subsequent to the original procedure or service. this circumstance may be reported by adding modifier 77 to the repeated procedure or service. note: this modifier should not be appended to an e/m service.
AY Item or service furnished to an esrd patient that is not for the treatment of esrd
CC Procedure code change (use 'cc' when the procedure code submitted was changed either for administrative reasons or because an incorrect code was filed)
GV Attending physician not employed or paid under arrangement by the patient's hospice provider
GW Service not related to the hospice patient's terminal condition
GY Item or service statutorily excluded, does not meet the definition of any medicare benefit or, for non-medicare insurers, is not a contract benefit
GZ Item or service expected to be denied as not reasonable and necessary
Q1 Routine clinical service provided in a clinical research study that is in an approved clinical research study
X5 Diagnostic services requested by another clinician: for reporting services by a clinician who furnishes care to the patient only as requested by another clinician or subsequent and related services requested by another clinician; this modifier is reported for patient relationships that may not be adequately captured by the above alternative categories; reporting clinician service examples include but are not limited to, the radiologist's interpretation of an imaging study requested by another clinician
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2013-01-01 Changed Medium Descriptor changed.
Pre-1990 Added Code added.
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