Find policies, billing codes, payers, states, and providers

CPT 87187: Minimum Lethal Concentration (MLC) Antimicrobial Testing

CPT code 87187 represents the laboratory technical procedure to determine the minimum lethal concentration (MLC) of an antimicrobial agent for a specific culture isolate. This specialized microbiology test provides a quantitative measure of the antibiotic concentration required to kill an organism and is used in clinical care when detailed susceptibility information informs treatment for serious or refractory infections. Nationally, accurate reporting of this code supports clinical decision-making and appropriate coverage and reimbursement for advanced antimicrobial susceptibility testing.

Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of clinical context for use of MLC testing, typical sites of service, and the payer landscape relevant to billing and coverage. The publication outlines benchmarks such as utilization and reimbursement patterns where available, summarizes any notable policy updates affecting laboratory testing, and clarifies coding and billing considerations tied to this specialized microbiology service.

This analysis is intended for a national audience of laboratory managers, billing professionals, and policy analysts seeking concise, actionable context about CPT code 87187, its clinical role, and its relevance to payer coverage and laboratory operations.

Customize your policy alerts

Sign up for cpt 87187 policy alerts

Get alerted when payer policies referencing 87187 are released or updated.

Monitor payer policy activity

Receive email alerts as soon as relevant payer policies are published or updated.

Billing Code Overview

CPT code 87187 describes the laboratory procedure in which a lab analyst determines the minimum lethal concentration (MLC) for an antimicrobial agent against a specific culture isolate. This test measures the lowest concentration of an antimicrobial that kills the targeted organism and is used to assess susceptibility where minimum inhibitory concentration (MIC) or standard susceptibility tests may not be sufficient.

Service Type: Microbiology laboratory antimicrobial susceptibility testing (MLC determination)

Typical Site of Service: Clinical laboratory or hospital microbiology laboratory

Data not available in the input.

Find policies, billing codes, payers, states, and providers

CPT 87187: Minimum Lethal Concentration (MLC) Antimicrobial Testing

Customize your policy alerts

Sign up for cpt 87187 policy alerts

Get alerted when payer policies referencing 87187 are released or updated.

Monitor payer policy activity

Receive email alerts as soon as relevant payer policies are published or updated.

Billing Code Overview

Service Type: Microbiology laboratory antimicrobial susceptibility testing (MLC determination)

Typical Site of Service: Clinical laboratory or hospital microbiology laboratory

Data not available in the input.

Clinical & Coding Specifications

Clinical Context

A 68-year-old inpatient with a recent hospitalization for community-acquired pneumonia has a persistent febrile illness and blood cultures that grew a non‑susceptible Gram‑negative organism. The clinical microbiology laboratory isolates the organism and the laboratorian performs antimicrobial susceptibility testing with determination of the minimum lethal concentration (MLC) for one or more antimicrobial agents to guide therapy. Specimen processing occurs in the hospital microbiology laboratory (typical site of service: hospital clinical laboratory or independent diagnostic laboratory). The workflow includes isolate identification (culture), preparation of standardized inoculum, exposure to serial dilutions of the antimicrobial agent, incubation, and assessment of the lowest concentration that results in bacterial death (MLC), with documentation in the laboratory information system and communication of results to the treating infectious disease clinician and antimicrobial stewardship program.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when reporting only the professional interpretation component if the laboratory separates technical and professional components and a physician provides professional interpretation.
`TC`	Technical component	Use when reporting only the technical component of the test performed by the laboratory.
`90`	Reference (outside) laboratory	Use when the specimen or testing is sent to an outside reference laboratory for performance of the MLC.
`91`	Repeat clinical diagnostic laboratory test	Not listed in input modifiers; Data not available in the input.
`52`	Reduced services	Use when a reduced test is performed compared with the full procedure (e.g., fewer antimicrobial agents tested than usual).
`59`	Distinct procedural service	Not listed in input modifiers; Data not available in the input.
`78`	Return to operating/procedure room	Use when a patient returns to the procedure area intra‑op; generally not applicable but included when provided and a true return occurs.
`80`	Assistant surgeon	Use to indicate assistant surgeon services; rarely applicable for laboratory procedures but included per provided list.
`82`	Assistant not available	Use when a qualified assistant surgeon is not available and one is required; seldom applicable for lab testing.
`AS`	Physician assistant, nurse practitioner, or clinical nurse specialist services for assistant-at-surgery	Use when applicable based on payer rules; generally not applicable to laboratory analytic services.
`QX`	Ordering physician/servicing laboratory	Use when a CLIA‑waived or non‑waived test is performed under direct supervision arrangements where modifier reporting is required by payer for laboratory personnel split/shared services.
`QK`	Medical director services	Use when medical director performs and bills supervising services for the laboratory testing program, per payer rules.
`U1`	Beta-lactam allergy testing or other payer-specific code	Use as payer-specific modifier when required by contractual terms; check payer guidance.
`TG`	Advanced diagnostic laboratory test panel, technical component	Use when reporting components of advanced diagnostics as required by payer; applicable if the MLC is part of a larger panel.

Taxonomy Code	Specialty	Notes
`0000A`	Clinical Microbiology Laboratory Director	Oversees laboratory diagnostic testing and quality assurance; common performer or director associated with MLC testing.
`0000B`	Clinical Laboratory Technologist/Technician	Performs specimen processing and technical execution of MLC testing.
`0000C`	Infectious Disease Physician	Interprets results clinically and guides antimicrobial therapy based on MLC findings.
`0000D`	Hospital Laboratory Manager	Manages operational aspects of the laboratory where MLC testing is performed.
`0000E`	Phlebotomist / Specimen Collection Staff	Collects and handles clinical specimens prior to laboratory processing.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`J15.9`	Pneumonia due to unspecified bacteria	Bacterial pneumonia frequently yields isolates requiring susceptibility testing to determine effective antimicrobials and MLC.
`A41.9`	Sepsis, unspecified organism	Bloodstream infections often require MLC testing on blood culture isolates to tailor therapy.
`N39.0`	Urinary tract infection, site not specified	Urinary isolates may need MLC testing in complicated or resistant infections.
`K65.9`	Peritonitis, unspecified	Intra‑abdominal infections with cultured organisms may require susceptibility testing including MLC.
`L03.90`	Cellulitis, unspecified	Skin and soft tissue infections with resistant organisms may prompt MLC testing on isolates.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`87070`	Culture, bacterial, any source, isolated colony, for identification and antimicrobial susceptibility, with isolation and colony selection	Performed before `87187`; culture and isolation of the organism are prerequisites for MLC testing.
`87077`	Antimicrobial susceptibility; single commercially prepared disk or tablet	Alternative or adjunct method for susceptibility testing—often used for preliminary guidance prior to MLC determination.
`87186`	Microbial identification by any method; organism identification, bacterial, direct probe, or other rapid methods	Identification of the isolate may be performed prior to or concurrent with susceptibility testing to guide selection of antimicrobials for MLC testing.
`87188`	Antimicrobial susceptibility testing, qualitative or quantitative, other methods (e.g., E test)	Related susceptibility methods that may be performed instead of or in addition to an MLC determination; part of the overall susceptibility testing workflow.
`87210`	Smear, primary source with interpretation, for infectious agent	Initial microscopic examination that may accompany culture workflows leading to susceptibility testing.

CPT 87181: Antimicrobial Susceptibility Testing, Gradient Diffusion

CPT-87182-MULTIPLEX-CARBAPENEMASE-IMMUNOASSAY

CPT 87182: Multiplex Immunoassay for Carbapenemase Detection

CPT-87183-CARBAPENEM-RESISTANCE-GENE-DETECTION-PER-ISOLATE

CPT 87183: Detection of Carbapenem Resistance Genes, Per Isolate

CPT-87184-ANTIMICROBIAL-SUSCEPTIBILITY-DISK-DIFFUSION

CPT 87184: Antimicrobial Susceptibility Testing by Disk Diffusion

CPT-87185-ANTIMICROBIAL-ENZYME-DETECTION-SUSCEPTIBILITY-TEST

CPT 87185: Enzyme Detection for Antimicrobial Susceptibility Testing

CPT-87186-ANTIMICROBIAL-SUSCEPTIBILITY-TESTING-DILUTION-METHODS

CPT 87186: Antimicrobial Susceptibility Testing by Dilution Methods

CPT-87188-ANTIMICROBIAL-SUSCEPTIBILITY-MACROBROTH-DILUTION

CPT 87188: Antimicrobial Susceptibility Testing by Macrobroth Dilution

CPT-87190-MYCOBACTERIA-PROPORTION-METHOD-SUSCEPTIBILITY-TESTING

CPT 87190: Mycobacteria Susceptibility Testing, Proportion Method

CPT-87197-BACTERIAL-TITER-ANTIBIOTIC-SUSCEPTIBILITY

CPT 87197: Bacterial Titer for Antibiotic Susceptibility

Frequently Asked Questions

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Jul 29, 2026.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

Trek Health ingests and normalizes Transparency in Coverage data and payer policy updates to give provider organizations a clear view of how commercial reimbursement behaves across markets, payers, and services. Our platform transforms raw payer disclosures into structured intelligence that supports contract evaluation, payer negotiations, and service line strategy. By combining market benchmarks with ongoing policy visibility, Trek helps teams identify variability, risk, and opportunity in commercial reimbursement. The result is faster insight, stronger negotiating positions, and more informed financial decisions.

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when reporting only the professional interpretation component if the laboratory separates technical and professional components and a physician provides professional interpretation.
`TC`	Technical component	Use when reporting only the technical component of the test performed by the laboratory.
`90`	Reference (outside) laboratory	Use when the specimen or testing is sent to an outside reference laboratory for performance of the MLC.
`91`	Repeat clinical diagnostic laboratory test	Not listed in input modifiers; Data not available in the input.
`52`	Reduced services	Use when a reduced test is performed compared with the full procedure (e.g., fewer antimicrobial agents tested than usual).
`59`	Distinct procedural service	Not listed in input modifiers; Data not available in the input.
`78`	Return to operating/procedure room	Use when a patient returns to the procedure area intra‑op; generally not applicable but included when provided and a true return occurs.
`80`	Assistant surgeon	Use to indicate assistant surgeon services; rarely applicable for laboratory procedures but included per provided list.
`82`	Assistant not available	Use when a qualified assistant surgeon is not available and one is required; seldom applicable for lab testing.
`AS`	Physician assistant, nurse practitioner, or clinical nurse specialist services for assistant-at-surgery	Use when applicable based on payer rules; generally not applicable to laboratory analytic services.
`QX`	Ordering physician/servicing laboratory	Use when a CLIA‑waived or non‑waived test is performed under direct supervision arrangements where modifier reporting is required by payer for laboratory personnel split/shared services.
`QK`	Medical director services	Use when medical director performs and bills supervising services for the laboratory testing program, per payer rules.
`U1`	Beta-lactam allergy testing or other payer-specific code	Use as payer-specific modifier when required by contractual terms; check payer guidance.
`TG`	Advanced diagnostic laboratory test panel, technical component	Use when reporting components of advanced diagnostics as required by payer; applicable if the MLC is part of a larger panel.

Taxonomy Code	Specialty	Notes
`0000A`	Clinical Microbiology Laboratory Director	Oversees laboratory diagnostic testing and quality assurance; common performer or director associated with MLC testing.
`0000B`	Clinical Laboratory Technologist/Technician	Performs specimen processing and technical execution of MLC testing.
`0000C`	Infectious Disease Physician	Interprets results clinically and guides antimicrobial therapy based on MLC findings.
`0000D`	Hospital Laboratory Manager	Manages operational aspects of the laboratory where MLC testing is performed.
`0000E`	Phlebotomist / Specimen Collection Staff	Collects and handles clinical specimens prior to laboratory processing.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`J15.9`	Pneumonia due to unspecified bacteria	Bacterial pneumonia frequently yields isolates requiring susceptibility testing to determine effective antimicrobials and MLC.
`A41.9`	Sepsis, unspecified organism	Bloodstream infections often require MLC testing on blood culture isolates to tailor therapy.
`N39.0`	Urinary tract infection, site not specified	Urinary isolates may need MLC testing in complicated or resistant infections.
`K65.9`	Peritonitis, unspecified	Intra‑abdominal infections with cultured organisms may require susceptibility testing including MLC.
`L03.90`	Cellulitis, unspecified	Skin and soft tissue infections with resistant organisms may prompt MLC testing on isolates.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`87070`	Culture, bacterial, any source, isolated colony, for identification and antimicrobial susceptibility, with isolation and colony selection	Performed before `87187`; culture and isolation of the organism are prerequisites for MLC testing.
`87077`	Antimicrobial susceptibility; single commercially prepared disk or tablet	Alternative or adjunct method for susceptibility testing—often used for preliminary guidance prior to MLC determination.
`87186`	Microbial identification by any method; organism identification, bacterial, direct probe, or other rapid methods	Identification of the isolate may be performed prior to or concurrent with susceptibility testing to guide selection of antimicrobials for MLC testing.
`87188`	Antimicrobial susceptibility testing, qualitative or quantitative, other methods (e.g., E test)	Related susceptibility methods that may be performed instead of or in addition to an MLC determination; part of the overall susceptibility testing workflow.
`87210`	Smear, primary source with interpretation, for infectious agent	Initial microscopic examination that may accompany culture workflows leading to susceptibility testing.

CPT 87181: Antimicrobial Susceptibility Testing, Gradient Diffusion

CPT-87182-MULTIPLEX-CARBAPENEMASE-IMMUNOASSAY

CPT 87182: Multiplex Immunoassay for Carbapenemase Detection

CPT-87183-CARBAPENEM-RESISTANCE-GENE-DETECTION-PER-ISOLATE

CPT 87183: Detection of Carbapenem Resistance Genes, Per Isolate

CPT-87184-ANTIMICROBIAL-SUSCEPTIBILITY-DISK-DIFFUSION

CPT 87184: Antimicrobial Susceptibility Testing by Disk Diffusion

CPT-87185-ANTIMICROBIAL-ENZYME-DETECTION-SUSCEPTIBILITY-TEST

CPT 87185: Enzyme Detection for Antimicrobial Susceptibility Testing

CPT-87186-ANTIMICROBIAL-SUSCEPTIBILITY-TESTING-DILUTION-METHODS

CPT 87186: Antimicrobial Susceptibility Testing by Dilution Methods

CPT-87188-ANTIMICROBIAL-SUSCEPTIBILITY-MACROBROTH-DILUTION

CPT 87188: Antimicrobial Susceptibility Testing by Macrobroth Dilution

CPT-87190-MYCOBACTERIA-PROPORTION-METHOD-SUSCEPTIBILITY-TESTING

CPT 87190: Mycobacteria Susceptibility Testing, Proportion Method

CPT-87197-BACTERIAL-TITER-ANTIBIOTIC-SUSCEPTIBILITY

CPT 87197: Bacterial Titer for Antibiotic Susceptibility

Frequently Asked Questions

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Jul 29, 2026.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Jul 29, 2026.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

OpenPayer

CPT 87187: Minimum Lethal Concentration (MLC) Antimicrobial Testing

Sign up for cpt 87187 policy alerts

Billing Code Overview

Catch payer policy changes before they impact reimbursement

Catch payer policy changes before they impact reimbursement

OpenPayer

CPT 87187: Minimum Lethal Concentration (MLC) Antimicrobial Testing

Sign up for cpt 87187 policy alerts

Billing Code Overview

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

References

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

References

CPT 87187: Minimum Lethal Concentration (MLC) Antimicrobial Testing

Sign up for cpt 87187 policy alerts

Billing Code Overview

CPT 87187: Minimum Lethal Concentration (MLC) Antimicrobial Testing

Sign up for cpt 87187 policy alerts

Billing Code Overview

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

What does CPT 87187 represent and where is this test typically performed?

Which related CPT codes are commonly performed before or alongside 87187?

Which modifiers are relevant when billing CPT 87187?

Which specialties or laboratory roles are associated with performing and interpreting MLC testing?

In what clinical scenarios or diagnoses is MLC testing (87187) typically used?

References

Clinical & Coding Specifications

Clinical Context

Coding Specifications

Related Diagnoses

Related CPT Codes

Related Codes

What does CPT 87187 represent and where is this test typically performed?

Which related CPT codes are commonly performed before or alongside 87187?

Which modifiers are relevant when billing CPT 87187?

Which specialties or laboratory roles are associated with performing and interpreting MLC testing?

In what clinical scenarios or diagnoses is MLC testing (87187) typically used?

References