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    v1.0.28
    OpenPayerBilling CodesOther and unspecified effects of external causesICD-10-CM t66-radiation-sickness-unspecified
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    ICD-10-CM Code For Radiation Sickness Unspecified: Group Overview

    The International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code group T66 includes radiation sickness and unspecified effects of ionizing radiation, covering acute and late sequelae affecting multiple organ systems. These ICD-10-CM diagnosis codes are used to document exposure-related conditions that capture severity, organ involvement, and clinical complexity of radiation injuries. Accurate coding within the ICD-10-CM T66 group supports complete clinical documentation and appropriate reimbursement.

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    ICD-10-CM T66: Radiation Sickness, Unspecified Overview

    This group represents diagnosis codes used for radiation sickness and unspecified effects of ionizing radiation on the body. The conditions target systemic and organ-specific effects from acute or chronic radiation exposure, including hematologic, gastrointestinal, dermatologic, and neurologic manifestations. Accurate coding matters for clinical records, claim processing, and ensuring appropriate tracking of radiation-related injuries for public health and reimbursement purposes.

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    When to Use

    Use a code from this group when a patient has documented clinical effects attributable to radiation exposure but the specific radiation-induced condition is unspecified or generalized. Select codes that reflect the documented severity and organ systems involved when additional specificity is available.

    ICD-10-CM Codes

    3 rows

    ICD-10-CM CodeDescription
    T66.XXXARadiation sickness, unspecified, initial encounter
    T66.XXXDRadiation sickness, unspecified, subsequent encounter
    T66.XXXSRadiation sickness, unspecified, sequela

    DRG Codes

    4 rows

    DRG CodeDescription
    922Other Injury, Poisoning and Toxic Effect Diagnoses with MCC
    923Other Injury, Poisoning and Toxic Effect Diagnoses without MCC
    949Aftercare with CC/MCC
    950Aftercare without CC/MCC

    Typical Clinical Scenarios

    • An adult emergency department patient presents within hours of an accidental high-dose occupational exposure to ionizing radiation after a reactor maintenance incident. The patient has nausea, vomiting, and erythema of exposed skin and requires acute evaluation and triage for radiation injury; a code from this group is assigned for the unspecified radiation sickness on the initial encounter. Typical codes: T66.XXXA
    • A middle-aged patient previously treated for malignancy with external beam radiation develops persistent constitutional symptoms and delayed hematologic abnormalities months after therapy, and presents to a clinic for ongoing management of late radiation effects when the precise nature of the radiation-induced syndrome is not otherwise specified; a code from this group is used for a subsequent encounter documenting the ongoing unspecified condition. Typical codes: T66.XXXD
    • An elderly patient with a history of undocumented radiologic exposure years earlier is admitted with deconditioning, recurrent infections, and progressive bone marrow suppression thought to be related to prior radiation exposure; the hospitalization documents the unspecified chronic sequelae of radiation as a contributing comorbidity and uses a code from this group to capture the unspecified radiation sickness status. Typical codes: T66.XXXS

    Related Codes

    T67-EFFECTS-OF-HEAT-AND-LIGHT

    ICD-10-CM Code For Effects Of Heat And Light: Group Overview

    T68-HYPOTHERMIA

    ICD-10-CM Code For Hypothermia: Group Overview

    T69-OTHER-EFFECTS-OF-REDUCED-TEMPERATURE

    ICD-10-CM Code For Other Effects Of Reduced Temperature: Group Overview

    T70-EFFECTS-OF-AIR-PRESSURE

    ICD-10-CM Code For Effects Of Air Pressure And Water Pressure: Group Overview

    T71-ASPHYXIATION-AND-RELATED-CONDITIONS

    ICD-10-CM Code For Asphyxiation: Group Overview

    T74-ADULT-AND-CHILD-ABUSE

    ICD-10-CM Code For Adult And Child Abuse Neglect And Other Maltreatment Confirmed: Group Overview

    T75-OTHER-AND-UNSPECIFIED-EFFECTS

    ICD-10-CM Code For Other And Unspecified Effects Of Other External Causes: Group Overview

    T76-ADULT-AND-CHILD-ABUSE-NEGLECT

    ICD-10-CM Code For Adult And Child Abuse Neglect And Other Maltreatment Suspected: Group Overview

    T78-ADVERSE-EFFECTS-NOT-ELSEWHERE-CLASSIFIED

    ICD-10-CM Code For Adverse Effects Not Elsewhere Classified: Group Overview

    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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