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    OpenPayerBilling CodesAmbulance and Other Transport Services and SuppliesHCPCS hcpcs-a0021-ambulance-service-outside-state-per-mile-transport
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    HCPCS A0021: Ambulance Service Outside State Per Mile, Transport (Medicaid Only)

    HCPCS Level II code A0021 describes an ambulance transport billed per mile for services provided outside the state for Medicaid beneficiaries; this code represents ambulance mileage as the service type and is typically used for ground ambulance transport where the typical site of service is en route between the pickup location and the destination across state lines for Medicaid-covered transports.

    For related coverage guidance, see recent payer policy updates: Percutaneous Arteriovenous Fistula Creation, Dialysis Services (ESRD) Coverage and Provider Requirements, Intradialytic Parenteral Nutrition - Medical Policy.

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    Clinical & Coding Specifications

    Clinical Context

    A typical patient scenario involves a Medicaid-enrolled adult who requires non-emergency interfacility or long-distance transport across state lines for a medically necessary service (for example, transfer from a rural hospital emergency department to a tertiary care center in another state for specialty neurosurgical evaluation). The ambulance service is billed on a per-mile basis when the transport occurs outside the state of the patient’s residence and is covered under Medicaid-specific billing rules. The clinical workflow: the sending clinician documents medical necessity for transport and level of care (basic life support or advanced life support) in the medical record; the ambulance provider logs origin and destination addresses, total miles, patient condition during transport, and staffing/medical interventions; the transport is authorized by the responsible facility/dispatcher per Medicaid policy; claims are submitted using the HCPCS Level II code A0021 with appropriate modifiers to indicate level of service, unusual circumstances, or payer-specific adjustments; supporting documentation (progress notes, transfer orders, and mileage logs) is retained for audit and medical review.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    99238Hospital discharge day management; final hospital discharge of patientOften completed after interfacility transfer when the sending facility documents discharge and transfer to ambulance transport.
    99221Initial hospital care, typically 30 minutesUsed by receiving hospital inpatient teams on admission after ambulance transport if the patient is admitted.
    99284Emergency department visit, moderate complexityMay describe the ED evaluation that led to decision for interfacility ambulance transfer.
    96372Therapeutic, prophylactic, or diagnostic injection; subcutaneous or intramuscularMay be performed prior to or during transport and documented as part of the transport care plan.
    94002Ventilation assist and management, initiation of invasive mechanical ventilation for inpatient, initial dayRelevant when a transported patient requires initiation of mechanical ventilation prior to or during transfer.

    Related Modifiers

    8 rows

    ModifierDescriptionWhen to Use
    22Modifier –22 (Increased Procedural Services) is used when a reported procedure is substantially more extensive than normally required. The CPT Manual and CMS state it may be appended only when the…- When to use: Append modifier -22 to a procedural CPT code when the service performed is substantially more extensive than the usual service described by that code — i.e., the procedure required…
    23Modifier -23 (Unusual Anesthesia) is used on anesthesia service CPT codes when a procedure that normally requires no anesthesia or only local anesthesia must be performed under general anesthesia…- Use modifier -23 only on anesthesia CPT codes (00100–01999) when a procedure that normally requires no anesthesia or only local anesthesia must be performed under general anesthesia because of…
    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…
    62Modifier 62 indicates that two surgeons function as co‑surgeons, each performing distinct parts of the same primary surgical procedure. It is appended to the primary procedure code (and any…- Use modifier -62 when two surgeons act as co‑surgeons (both primary surgeons) on a single definitive primary procedure, each performing distinct parts of the same surgical procedure (append -62 to…
    78CPT modifier -78 indicates an unplanned, related return to the operating or procedure room by the same provider during the global postoperative period. It is appended when treatment for a…- Use modifier -78 when an unplanned, related complication during the original procedure’s global postoperative period requires the patient to return to a formal operating or procedure room and the…
    80CPT® Modifier 80 (Assistant Surgeon) is appended to a surgical CPT code when a physician (MD or DO) provides full, continuous assistance throughout the operative procedure. It is intended only for…- Use CPT Modifier -80 when a physician (MD or DO) serves as an assistant surgeon and provides full, continuous assistance throughout the entire operative procedure; append -80 to the surgical CPT…
    82Modifier 82 is appended to a surgical CPT code to indicate that an attending physician acted as an assistant because a qualified resident surgeon was unavailable. In teaching hospitals it documents…- When to use: Append modifier 82 in teaching-hospital settings to indicate a physician served as an assistant surgeon because a qualified resident surgeon was unavailable (includes situations where…

    Related Provider Taxonomies

    8 rows

    Taxonomy Code
    207RH0000X
    208D00000X
    208000000X
    374U00000X
    207QS0010X
    207RP1002X
    2355S0801X
    2251P0200X

    Related Payer Policy Updates

    Specialty: Dialysis/Renal Replacement1 / 3

    10 rows

    PolicyPayerEffective Date
    Percutaneous Arteriovenous Fistula CreationAmeriHealth Caritas2026-08-01
    Dialysis Services (ESRD) Coverage and Provider RequirementsMississippi Division of Medicaid2026-08-01
    Intradialytic Parenteral Nutrition - Medical PolicyHealth-New-England2026-07-01
    Total Parenteral Nutrition and Intradialytic Parenteral NutritionCentene2026-05-01
    End Stage Renal Disease (ESRD): Renal Dialysispriority health2026-02-01
    Home Hemodialysis (HHD) Coverage Criteriasierra health and life2026-01-01
    Home Hemodialysis (HHD) — Coverage CriteriaUnitedHealthcare2026-01-01
    Dialysis services (acute and chronic hemodialysis and peritoneal dialysis)UnitedHealthcare2026-01-01
    Staff-Assisted Home HemodialysisCigna2025-11-15
    Parsabiv (etelcalcetide) Coverage for Secondary HyperparathyroidismMolina Healthcare2025-10-09

    Related Codes

    HCPCS-A0080-VOLUNTEER-NON-EMERGENCY-TRANSPORTATION-MILEAGE

    HCPCS Level II A0080: Non-Emergency Volunteer Vehicle Transport, Per Mile

    HCPCS-A0090-NON-EMERGENCY-TRANSPORTATION-MILE-PRIVATE-VEHICLE

    HCPCS A0090: Non-Emergency Transportation, Per Mile

    HCPCS-A0100-NON-EMERGENCY-TAXI-TRANSPORTATION

    HCPCS A0100: Non-Emergency Transportation, Taxi

    HCPCS-A0110-NON-EMERGENCY-BUS-TRANSPORTATION

    HCPCS Level II A0110: Non-Emergency Bus or Carrier Transportation

    HCPCS-A0120-NON-EMERGENCY-MINI-BUS-TRANSPORTATION

    HCPCS Level II A0120: Non‑Emergency Transportation by Mini‑Bus or Mountain Transport

    HCPCS-A0130-WHEELCHAIR-VAN-NON-EMERGENCY-TRANSPORTATION

    HCPCS Level II A0130: Non-Emergency Transportation, Wheelchair Van

    HCPCS-A0140-NON-EMERGENCY-AIR-TRANSPORTATION

    HCPCS Level II A0140: Non-Emergency Transportation and Air Travel

    HCPCS-A0160-NON-EMERGENCY-TRANSPORTATION-CASE-WORKER-SOCIAL-WORKER-PER-MILE

    HCPCS Level II A0160: Non-Emergency Transportation by Case Worker

    HCPCS-A0180-ANCILLARY-LODGING-NON-EMERGENCY-TRANSPORTATION

    HCPCS Level II A0180: Non-Emergency Transportation Lodging-Recipient

    HCPCS-A0190-NON-EMERGENCY-TRANSPORTATION-MEALS-RECIPIENT

    HCPCS A0190: Non-Emergency Transportation Ancillary Meals-Recipient

    Showing 1–10 of 40

    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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