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    v1.0.28
    OpenPayerBilling CodesOther and unspecified effects of external causesICD-10-CM t78-adverse-effects-not-elsewhere-classified
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    ICD-10-CM Code For Adverse Effects Not Elsewhere Classified: Group Overview

    The International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code group T78 includes adverse effects from drugs, medicaments, biological substances, and unspecified allergic or toxic reactions not classified elsewhere, covering hypersensitivity reactions, anaphylaxis, and other systemic or localized adverse responses. These ICD-10-CM diagnosis codes are used to document clinical scenarios such as drug-induced allergic reactions, toxic effects of substances, and complications from medicinal agents, capturing severity, organ system involvement, and clinical complexity relevant to this group. Accurate coding within the ICD-10-CM T78 group supports proper claim adjudication and complete clinical documentation that aligns with appropriate reimbursement.

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    ICD-10-CM T78: Adverse Effects, Not Elsewhere Classified Overview

    The ICD-10-CM T78 code group captures adverse effects from drugs, medicaments, and biological substances that are not classified elsewhere, including unspecified allergic reactions and toxic effects. These diagnoses affect multiple body systems depending on the agent involved and can range from mild hypersensitivity to severe systemic reactions. Accurate coding matters for proper claim adjudication and to reflect clinical complexity that affects treatment and follow-up.

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    When to Use

    Use a code from this group when a patient experiences an adverse effect or toxic reaction from a drug, medicament, or biological substance and no more specific ICD-10-CM code applies. Select the code that reflects the documented clinical manifestation and severity, including organ system involvement when specified.

    ICD-10-CM Codes

    81 rows

    ICD-10-CM CodeDescription
    T78.00XAAnaphylactic reaction due to unspecified food, initial encounter
    T78.00XDAnaphylactic reaction due to unspecified food, subsequent encounter
    T78.00XSAnaphylactic reaction due to unspecified food, sequela
    T78.01XAAnaphylactic reaction due to peanuts, initial encounter
    T78.01XDAnaphylactic reaction due to peanuts, subsequent encounter
    T78.01XSAnaphylactic reaction due to peanuts, sequela
    T78.02XAAnaphylactic reaction due to shellfish (crustaceans), initial encounter
    T78.02XDAnaphylactic reaction due to shellfish (crustaceans), subsequent encounter
    T78.02XSAnaphylactic reaction due to shellfish (crustaceans), sequela
    T78.03XAAnaphylactic reaction due to other fish, initial encounter
    T78.03XDAnaphylactic reaction due to other fish, subsequent encounter
    T78.03XSAnaphylactic reaction due to other fish, sequela
    T78.04XAAnaphylactic reaction due to fruits and vegetables, initial encounter
    T78.04XDAnaphylactic reaction due to fruits and vegetables, subsequent encounter
    T78.04XSAnaphylactic reaction due to fruits and vegetables, sequela
    T78.05XAAnaphylactic reaction due to tree nuts and seeds, initial encounter
    T78.05XDAnaphylactic reaction due to tree nuts and seeds, subsequent encounter
    T78.05XSAnaphylactic reaction due to tree nuts and seeds, sequela
    T78.06XAAnaphylactic reaction due to food additives, initial encounter
    T78.06XDAnaphylactic reaction due to food additives, subsequent encounter

    Showing 1–20 of 81

    DRG Codes

    10 rows

    DRG CodeDescription
    791Prematurity with Major Problems
    793Full Term Neonate with Major Problems
    915Allergic Reactions with MCC
    916Allergic Reactions without MCC
    917Poisoning and Toxic Effects of Drugs with MCC
    918Poisoning and Toxic Effects of Drugs without MCC
    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 presents to the emergency department with sudden-onset generalized urticaria, facial swelling, and difficulty breathing shortly after receiving a new intravenous antibiotic in the hospital. Immediate treatment for an acute allergic reaction is given; the encounter documents the adverse effect of a correctly administered antibiotic causing anaphylactic-type symptoms, so an adverse-effect code from this group is assigned to indicate the drug-induced hypersensitivity. Typical codes: T78.2XXA, T78.2XXD
    • An outpatient cardiology clinic documents an elderly patient who reports recurrent episodes of dizziness and hypotension after starting a new antihypertensive medication several weeks ago; the medication was not overdosed or misused. Because these are ongoing adverse effects attributable to a properly administered therapeutic drug and are being managed on an outpatient basis, a code from this group for adverse effect, subsequent encounter can be used to capture the drug-related complication. Typical codes: T78.2XXD, T78.2XXS
    • A pediatric patient is brought to urgent care with a localized pruritic rash and mild wheeze that began immediately after a bee sting at a playground; the child receives treatment and is discharged with follow-up. The visit documents an adverse reaction to an insect sting (external cause) requiring acute care, so an acute encounter code from this group is assigned to indicate the external-cause adverse effect. Typical codes: T78.3XXA, T78.3XXD

    Related Codes

    T66-RADIATION-SICKNESS-UNSPECIFIED

    ICD-10-CM Code For Radiation Sickness Unspecified: Group Overview

    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

    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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