2027 ICD-10-CM Diagnosis Code T78.19XAOther adverse food reactions, not elsewhere classified, initial encounter
T78.19XA is a billable ICD-10-CM diagnosis code for other adverse food reactions, not elsewhere classified, 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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 922 through 923. The code is not accepted as a principal diagnosis by the Medicare Code Editor. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Allergic reactions.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T78.19XA.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Adverse drug interaction
- Adverse medication interaction with food
- Adverse reaction caused by monosodium glutamate
- Adverse reaction to chewing gum additive
- Adverse reaction to fig
- Adverse reaction to food
- Adverse reaction to food additive
- Allergic angioedema
- Allergic angioedema due to ingested food
- Allergic bronchospasm caused by dietary substance
- Allergic reaction caused by fish
- Allergic reaction caused by food additive
- Allergic reaction caused by fruit
- Allergic reaction caused by mollusk
- Allergic reaction caused by peanut
- Allergic reaction caused by seafood
- Allergic reaction caused by seed
- Allergic reaction caused by shellfish
- Allergic reaction caused by tree nut
- Allergic reaction caused by vegetable
- Allergic reaction to food
- Allergic urticaria caused by ingested food
- Allergy to food
- Bronchospasm
- Enteral and supplement feeds adverse reaction
- Food-induced angioedema-urticaria
- Headache caused by monosodium glutamate
- Hypersensitivity reaction caused by food
- Intolerance to monosodium glutamate
- Medication interaction with food
- Non-allergic hypersensitivity reaction caused by sulfite
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 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to T78.19XA: its own notes plus those printed at T78.1, T78, block T66-T78, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify the type of reaction, if applicable
- code to identify any retained foreign body, if applicable (Z18.-)
Code Also
A second code may be needed to fully describe the condition; the note gives no sequencing direction.
- if applicable, place of occurrence, such as:
- highway rest stop (Y92.523)
- school (private) (public) (state) as the place of occurrence of the external cause (Y92.21-)
- service areas as the place of occurrence of the external cause (Y92.52-)
- single-family non-institutional (private) house as the place of occurrence of the external cause (Y92.01-)
- transport vehicle as the place of occurrence of the external cause (Y92.81-)
Notes
General instructions on how these codes are used.
- Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category T78
- Ainitial encounter this code
- Dsubsequent encounter
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name T78.19XA, its category, or a range that includes it.
Excludes1 1
These codes carry an Excludes1 note naming T78.19XA: they are not reported together with it, unless the two conditions are unrelated.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Food Allergy
A food allergy is an abnormal immune system reaction to certain foods. Your immune system normally protects you from germs. But if you have a food allergy, your immune system mistakenly reacts to certain foods as if they were harmful. This reaction is usually mild. But in some cases, it can be serious or even life-threatening.
The full article covers:
- What is a food allergy?
- Who is more likely to develop a food allergy?
- What are the symptoms of food allergies?
- How are food allergies diagnosed?
- What are the treatments for food allergies?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Code History & ChangesHistory
Replacement T78.19XA replaces the following previously assigned code(s):
- T78.1XXA - Oth adverse food reactions, not elsewhere classified, init
Questions About T78.19XAOverview
Is T78.19XA (Other adverse food reactions, not elsewhere classified) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other adverse food reactions, not elsewhere classified, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character A in T78.19XA mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for other adverse food reactions, not elsewhere classified, such as an emergency visit or first evaluation.
What MS-DRG does T78.19XA group to?
On inpatient claims, other adverse food reactions, not elsewhere classified, initial encounter maps to MS-DRG 923, 922, with relative weights from 0.9980 to 1.6248 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T78.19XA be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because other adverse food reactions, not elsewhere classified, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
Can T78.19XA be reported with a code from T78.0?
Not as a rule. The Excludes1 note at T78.1, which applies to T78.19XA, lists "anaphylactic reaction or shock due to adverse food reaction (T78.0-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
