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    v1.0.28
    OpenPayerBilling CodesTherapeutic Drug AssaysCPT cpt-80339-antiepileptic-drug-detection-one-to-three
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    CPT 80339: Antiepileptic Drug Assay, 1–3 Drugs

    CPT code 80339 describes a laboratory assay to detect or measure the presence of one to three antiepileptic (anticonvulsant or antiseizure) medications in a patient specimen; this is a toxicology/therapeutic drug monitoring service typically performed in a clinical laboratory or hospital lab setting using patient blood or serum and reported when the specific antiepileptics tested are not specified by other CPT codes.

    For related coverage guidance, see recent payer policy updates: Epithelial Cell Cytology in Breast Cancer Risk Assessment, Chemotherapy Observation or Inpatient Hospitalization (for New Mexico Only), Antibody-Drug Conjugates.

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    Table of contents

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    Clinical & Coding Specifications

    Clinical Context

    A 28-year-old patient with known epilepsy presents to an outpatient neurology clinic for routine therapeutic drug monitoring after seizure recurrence. The clinician orders serum antiepileptic drug levels to confirm adherence, assess subtherapeutic levels, and evaluate potential drug interactions. A phlebotomy draw is performed in the clinic or at an affiliated laboratory; the specimen is sent to the clinical laboratory where a laboratory analyst performs quantitative testing to measure the presence or amount of one to three antiepileptic medications not specified by other CPT codes. Typical workflow: clinician documents indication and orders the test → specimen collected at an outpatient clinic, hospital outpatient lab, or reference lab → specimen accessioned and analyzed by laboratory personnel using appropriate immunoassay or mass spectrometry methods → results reported to the ordering provider for dose adjustment or clinical decision-making. Typical site of service: outpatient clinic, hospital outpatient laboratory, or independent clinical laboratory. Typical patient scenario: routine monitoring of anticonvulsant therapy, evaluation after breakthrough seizures, suspected toxicity, or assessment when changing therapy or adding interacting medications.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    80307Phenobarbital; quantitativeAlternative specific drug level code when phenobarbital is one of the drugs requested; used if testing for phenobarbital specifically
    80306Carbamazepine; quantitativeSpecific code for quantitative carbamazepine level testing when that drug is being measured
    80310Phenytoin; quantitativeSpecific code for quantitative phenytoin level testing when that drug is measured
    80053Comprehensive metabolic panel; 14 testsCommonly ordered concurrently to assess metabolic status, electrolytes, and organ function affecting drug levels
    36415Collection of venous blood by venipunctureSpecimen collection code typically billed by the phlebotomy service when blood is drawn for antiepileptic levels

    Related Modifiers

    6 rows

    ModifierDescriptionWhen to Use
    26Modifier 26 (Professional Component) identifies and bills only the professional portion of a split service — the physician’s interpretation, report, and medical judgment — when the technical…- Use CPT Modifier -26 when you are billing only the professional component (PC) of a split‑bill eligible service—i.e., you performed the physician interpretation, medical judgment and prepared a…
    52Modifier ‑52 (Reduced Services) indicates that a service or procedure was partially reduced or omitted at the provider’s discretion, allowing reporting of the basic procedure number with a qualifier…- Use modifier -52 when a physician or qualified health professional electively reduces or omits part of a procedure or service (for example, performing fewer required views or omitting a portion of…
    53Modifier 53 (Discontinued Procedure) signals that a surgical or diagnostic service was begun by the physician but terminated because of extenuating circumstances that threatened the patient’s…- Use modifier -53 when a physician/qualified healthcare professional has started a surgical or diagnostic procedure (e.g., anesthesia administered, incision or scope insertion) and then discontinues…
    59Modifier 59 indicates a distinct procedural service when two procedures that are not normally billed together are clinically and procedurally separate. The CPT definition (as reiterated by CMS)…- Use modifier -59 to report a distinct procedural service when documentation supports that the procedure reported is not normally billed together with another service on the same day because of a…
    90Modifier ‑90 (Reference/Outside Laboratory) indicates that a laboratory test was performed by an entity other than the treating or reporting provider. The American Medical Association defines…- Use CPT modifier -90 when a laboratory test is performed by an outside/reference laboratory (an entity other than the treating or reporting physician or qualified professional) and the claim needs…
    91Modifier 91 — “Repeat Clinical Diagnostic Laboratory Test” — is appended when the exact same CPT laboratory test is performed more than once for the same patient on the same day because serial,…- Use modifier 91 when the exact same CPT laboratory test is performed more than once on the same patient on the same date because serial or repeated testing is medically necessary to monitor…

    Related Provider Taxonomies

    8 rows

    Taxonomy CodeSpecialtyNotes
    207RG0100XGastroenterology PhysicianAn internist who specializes in diagnosis and treatment of diseases of the digestive organs including the stomach, bowels, liver and gallbladder. This…
    207L00000XAnesthesiology PhysicianAn anesthesiologist is trained to provide pain relief and maintenance, or restoration, of a stable condition during and immediately following an opera…
    208000000XPediatrics PhysicianA pediatrician is concerned with the physical, emotional and social health of children from birth to young adulthood. Care encompasses a broad spectru…
    2084P0800XPsychiatry PhysicianA Psychiatrist specializes in the prevention, diagnosis, and treatment of mental disorders, emotional disorders, psychotic disorders, mood disorders, …
    363LF0000XFamily Nurse PractitionerPhysician Assistants & Advanced Practice Nursing Providers · Nurse Practitioner
    261QU0200XUrgent Care Clinic/CenterAmbulatory Health Care Facilities · Clinic/Center
    246XC2903XVascular Specialist/Technologist CardiovascularA vascular technologist, also known as a vascular sonographer, creates images of blood vessels and collects data that help physicians diagnose disorde…
    320900000XIntellectual and/or Developmental Disabilities Community Based Residential Treatment FacilityA home-like residential facility providing habilitation, support and monitoring services to individuals diagnosed with intellectual and/or development…

    Related ICD-10-CM Codes

    24 rows

    ICD-10-CM CodeDescription
    F10.27Alcohol dependence with alcohol-induced persisting dementia
    F19.97Other psychoactive substance use, unspecified with psychoactive substance-induced persisting dementia
    G31.9Degenerative disease of nervous system, unspecified
    G40.001Localization-related (focal) (partial) idiopathic epilepsy and epileptic syndromes with seizures of localized onset, not intractable, with status epilepticus
    G40.101Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, not intractable, with status epilepticus
    G40.109Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, not intractable, without status epilepticus
    G40.119Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with simple partial seizures, intractable, without status epilepticus
    G40.209Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, not intractable, without status epilepticus
    G40.219Localization-related (focal) (partial) symptomatic epilepsy and epileptic syndromes with complex partial seizures, intractable, without status epilepticus
    G40.309Generalized idiopathic epilepsy and epileptic syndromes, not intractable, without status epilepticus

    Showing 1–10 of 24

    Related Payer Policy Updates

    Specialty: Hematology/Oncology1 / 2

    4 rows

    PolicyPayerEffective Date
    Epithelial Cell Cytology in Breast Cancer Risk AssessmentOscar Health2026-10-01
    Chemotherapy Observation or Inpatient Hospitalization (for New Mexico Only)UnitedHealthcare2026-08-01
    Antibody-Drug ConjugatesPremera Bluecross2026-08-01
    Umbilical Cord Blood Harvesting and Storage for Future Use (for Indiana Only)UnitedHealthcare2026-08-01

    Related Codes

    CPT-80143-ACETAMINOPHEN-QUANTITATIVE-SERUM-ASSAY

    CPT 80143: Acetaminophen Quantitative Assay

    CPT-80145-ADALIMUMAB-LEVEL-ASSAY-THERAPEUTIC-DRUG-MONITORING

    CPT 80145: Adalimumab Quantitative Drug Level Assay

    CPT-80150-AMIKACIN-QUANTITATIVE-ASSAY-THERAPEUTIC-DRUG-MONITORING

    CPT 80150: Amikacin Quantitative Serum Level

    CPT-80151-AMIODARONE-QUANTITATIVE-SERUM-ASSAY

    CPT 80151: Amiodarone Quantitative Drug Level Assay

    CPT-80155-CAFFEINE-LEVEL-TESTING

    CPT 80155: Caffeine Level Quantification

    CPT-80156-CARBAMAZEPINE-TOTAL-LEVEL-LAB-ASSAY

    CPT 80156: Carbamazepine Total Level (Serum)

    CPT-80157-FREE-CARBAMAZEPINE-ASSAY

    CPT 80157: Free Carbamazepine Quantitative Assay

    CPT-80158-CYCLOSPORINE-QUANTITATIVE-ASSAY-LAB

    CPT 80158: Cyclosporine Quantitation, Laboratory

    CPT-80159-CLOZAPINE-LEVEL-ASSAY-THERAPEUTIC-DRUG-MONITORING

    CPT 80159: Clozapine Level Measurement

    CPT-80161-CARBAMAZEPINE-EPOXIDE-QUANTITATIVE-ASSAY

    CPT 80161: Carbamazepine 10,11-Epoxide Level, Quantitative

    Showing 1–10 of 87

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    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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