Summary & Overview
CPT 80156: Carbamazepine Total Level Laboratory Assay
Headline: CPT code 80156 — Lab assay for total carbamazepine level
CPT code 80156 identifies a laboratory test that measures the total serum concentration of carbamazepine, capturing both the bound and free fractions. This assay supports therapeutic drug monitoring for clinicians managing epilepsy and other neurologic or psychiatric conditions treated with carbamazepine. Accurate total-level measurement is important for dosing decisions, toxicity assessment, and documentation of adherence.
Major national payers commonly covering this service include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Coverage policies and prior-authorization requirements vary by payer and clinical context.
This publication explains the clinical purpose of CPT code 80156, typical service settings, and the types of operational and policy considerations readers can expect to find in the full document. Topics include payer coverage and coding considerations, common claim modifiers and technical components, and clinical context for when total carbamazepine testing is ordered. Where specific input data was not provided, the text notes that the information is not available in the input. The content is written for a national audience of coding professionals, laboratory managers, and policy analysts.
Billing Code Overview
CPT code 80156 describes a laboratory assay measuring the total concentration of carbamazepine in a patient specimen. The test quantifies both bound and unbound (free) carbamazepine, providing a single value that reflects the overall drug level in the sample.
Service type: Therapeutic drug monitoring / toxicology laboratory test
Typical site of service: Clinical laboratory or hospital laboratory
Data not available in the input.
Clinical & Coding Specifications
Clinical Context
A 28-year-old patient with focal epilepsy treated with carbamazepine presents for routine therapeutic drug monitoring after a recent dose adjustment due to seizure recurrence. The clinician orders a laboratory assay to measure the total carbamazepine concentration (bound plus unbound) to confirm therapeutic range and assess adherence, drug interactions, or toxicity risk. A phlebotomy technician collects a serum specimen at a scheduled outpatient laboratory draw or hospital inpatient lab, following facility specimen-handling protocol. The specimen is labeled and transported to the clinical laboratory where a lab analyst performs the technical assay corresponding to 80156. Results are reported to the ordering provider and incorporated into medication management decisions; reflex testing or repeat levels may be ordered if results are inconsistent with clinical status or timing of last dose.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | When reporting the physician or pathologist interpretation separate from the lab’s technical component, if applicable for associated services |
90 | Reference (outside) laboratory | When the performing lab is an outside reference laboratory that reports the result |
91 | Repeat clinical diagnostic laboratory test | When the test is repeated on the same date to confirm an unexpected result |
52 | Reduced services | When only a portion of the full test is performed due to clinical or technical limitations |
53 | Discontinued procedure | When specimen collection or testing was started but discontinued for patient safety or other valid reason |
59 | Distinct procedural service | Not in raw list — excluded per strict rules |
76 | Repeat procedure by same physician — Not provided — excluded | |
11 | Multiple procedures — When billing under special payer rules for multiple lab services on same date when required by payer | |
22 | Increased procedural service | When additional work or complexity is documented for the lab test beyond typical processing |
78 | Unplanned return to the operating/procedure room — rarely applicable but present in list | When related to a procedural complication requiring additional lab work tied to re-operation |
80 | Assistant surgeon — rarely applicable | If an assistant surgeon’s involvement generates billable interpretive technical activity related to specimen handling |
90 | Reference (outside) laboratory — duplicate entry removed | When the specimen is sent to an external reference lab for 80156 testing |
| Taxonomy Code | Specialty | Notes |
|---|---|---|
| 183500000X | Clinical Pathology | Clinical chemists and laboratory physicians overseeing therapeutic drug monitoring |
| 207L00000X | Neurology | Ordering providers managing epilepsy and overseeing carbamazepine levels |
| 208000000X | Family Medicine | Primary care clinicians ordering monitoring for chronic therapy |
| 207Q00000X | Neurological Surgery | Occasionally involved when anticonvulsant levels are monitored perioperatively |
Related Diagnoses
| ICD-10 Code | Description | Clinical Relevance |
|---|---|---|
G40.909 | Epilepsy, unspecified, not intractable, without status epilepticus | Common indication for monitoring carbamazepine blood concentration to maintain therapeutic dosing |
G40.309 | Generalized idiopathic epilepsy and epileptic syndromes, intractable, without status epilepticus | Therapeutic drug level monitoring for seizure control and toxicity prevention in difficult-to-control epilepsy |
F31.3 | Bipolar disorder, current episode depressed, moderate | Carbamazepine is sometimes used as a mood stabilizer; levels may be monitored for efficacy and safety |
G43.909 | Migraine, unspecified, not intractable, without status migrainosus | Off-label or adjunctive uses of anticonvulsants may prompt level checks in select patients |
T43.592A | Poisoning by other antiepileptic and sedative-hypnotic drugs, initial encounter | Toxic levels of carbamazepine require quantitative measurement for management |
Related CPT Codes
| CPT Code | Description | Relationship to This Procedure |
|---|---|---|
36415 | Collection of venous blood by venipuncture | Specimen collection required before performing the 80156 assay |
82570 | Drug assay, qualitative; multiple drug classes — Not typically used for carbamazepine levels | Not applicable — included only if screening panels are performed prior to specific quantification |
80307 | Drug test(s), definitive; multiple drug classes, includes confirmation | May be used when confirmation testing using mass spectrometry is performed for therapeutic or forensic purposes |
80156 | Carbamazepine; total level (bound + unbound) | The primary technical assay code describing the laboratory analysis performed |
80053 | Comprehensive metabolic panel | Often ordered concurrently to assess organ function that affects drug metabolism and toxicity risk |