2026 ICD-10-CM Diagnosis Code T78.2XXAAnaphylactic shock, unspecified, initial encounter
T78.2XXA is a billable ICD-10-CM diagnosis code for anaphylactic shock, unspecified, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 915 through 916. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Allergic reactions.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Allergic reaction caused by Hevea brasiliensis latex protein
- Allergic reaction caused by hymenoptera venom
- Allergic reaction caused by insect bite and/or insect sting
- Allergic reaction to bee sting
- Allergic reaction to wasp sting
- Anaphylactic shock
- Anaphylaxis
- Anaphylaxis caused by Hevea brasiliensis latex protein
- Anaphylaxis caused by honey bee venom
- Anaphylaxis caused by hornet venom
- Anaphylaxis caused by hymenoptera venom
- Anaphylaxis caused by insect bite and/or insect sting
- Anaphylaxis caused by insect venom
- Anaphylaxis caused by low temperature
- Anaphylaxis caused by venom
- Anaphylaxis due to mast cell disorder
- Bee sting-induced anaphylaxis
- Drug-induced anaphylaxis
- Exercise anaphylaxis
- Food-dependent exercise-induced anaphylaxis
- Iatrogenic non-allergic anaphylaxis
- Idiopathic anaphylaxis
- Insulin adverse reaction
- Insulin-induced anaphylaxis
- Late effect of accidental injury
- Localized anaphylaxis
- Non-allergic anaphylaxis
- Non-allergic anaphylaxis caused by organic phosphorous compound
- Seminal fluid-induced anaphylaxis
- Wasp sting-induced anaphylaxis
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Adverse effects, not elsewhere classified (T78). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Anaphylaxis
an acute hypersensitivity reaction due to exposure to a previously encountered antigen. the reaction may include rapidly progressing urticaria, respiratory distress, vascular collapse, systemic shock, and death.Exercise-Induced Allergies
allergic reactions following a period of exercise. elevated serum histamine and tryptase levels and cutaneous mast cell degranulation are often associated with post-exertional allergic reactions which sometimes are triggered only in combination with prior consumption of a specific food such as wheat. allergic symptoms produced post-exercise range from skin eruption, asthma, bronchospasm, and anaphylaxis.Passive Cutaneous Anaphylaxis
an evanescent cutaneous reaction occurring when antibody is injected into a local area on the skin and antigen is subsequently injected intravenously along with a dye. the dye makes the rapidly occurring capillary dilatation and increased vascular permeability readily visible by leakage into the reaction site. pca is a sensitive reaction for detecting very small quantities of antibodies and is also a method for studying the mechanisms of immediate hypersensitivity.Venom Hypersensitivity
allergic reaction to venoms in insect bites and stings that is triggered by the immune system (i.e., histamine release).Histamine Release
the secretion of histamine from mast cell and basophil granules by exocytosis. this can be initiated by a number of factors, all of which involve binding of ige, cross-linked by antigen, to the mast cell or basophil's fc receptors. once released, histamine binds to a number of different target cell receptors and exerts a wide variety of effects.Anaphylactoid/Anaphylaxis|Anaphylactoid / Anaphylaxis
acute immune response that occurs from exposure to an allergen. it can be anaphylaxis or like anaphylaxisAnaphylaxis
an acute hypersensitive immune response that occurs from exposure to an allergen. it results from the release of histamine and histamine-like substances from mast cells, and can present with breathing difficulty due to narrowed airways, dizziness and hypotension, skin rash, weak pulse, nausea and vomiting.Anaphylaxis, CTCAE|Anaphylaxis|Anaphylaxis
a disorder characterized by an acute inflammatory reaction resulting from the release of histamine and histamine-like substances from mast cells, causing a hypersensitivity immune response. clinically, it presents with breathing difficulty, dizziness, hypotension, cyanosis and loss of consciousness and may lead to death.Grade 3 Anaphylaxis, CTCAE|Grade 3 Anaphylaxis
symptomatic bronchospasm, with or without urticaria; parenteral intervention indicated; allergy-related edema/angioedema; hypotensionGrade 4 Anaphylaxis, CTCAE|Grade 4 Anaphylaxis
life-threatening consequences; urgent intervention indicatedGrade 5 Anaphylaxis, CTCAE|Grade 5 Anaphylaxis
death
Patient EducationClinical
Anaphylaxis
Anaphylaxis is a serious allergic reaction. It can begin very quickly, and symptoms may be life-threatening. The most common causes are reactions to foods (especially peanuts), medications, and stinging insects. Other causes include exercise and exposure to latex. Sometimes no cause can be found.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T78.2XXA to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T78.2XXAOverview
Is T78.2XXA (Anaphylactic shock, unspecified) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report anaphylactic shock, unspecified, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T78.2XXA mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for anaphylactic shock, unspecified, such as an emergency visit or first evaluation.
What MS-DRG does T78.2XXA group to?
When anaphylactic shock, unspecified, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 915, 916, with relative weights from 0.6663 to 1.6816 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of T78.2XXA?
Under the General Equivalence Mappings, anaphylactic shock, unspecified, initial encounter converts to ICD-9-CM 995.0 (other anaphylactic react). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
