2027 ICD-10-CM Diagnosis Code T80.59XAAnaphylactic reaction due to other serum, initial encounter

ICD-10-CM Codes›S00–T88›T80-T88›T80

ICD-10-CM T80.59XA
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

T80.59XA is a billable ICD-10-CM diagnosis code for anaphylactic reaction due to other serum, 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 791, 793, 915 through 916. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 6 closely related codes. Coders also document this condition as anaphylactic shock. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complication of other surgical or medical care, injury, initial encounter.

Code Identity

ICD-10-CM Code
T80.59XA
Billable Status
Yes — Valid for Submission
Code Describes
Anaphylactic reaction due to other serum, initial encounter
Short Description
Anaphylactic reaction due to other serum, initial encounter
Same as the full description in the CMS dataset.
Parent Code
T80.59
Anaphylactic reaction due to other serum

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT80-T88Complications of surgical and medical care, not elsewhere classified
CategoryT80Complications following infusion, transfusion and therapeutic injection
This CodeT80.59XAAnaphylactic reaction due to other serum, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Anaphylactic shock
  • Anaphylactic shock caused by serum
  • Anaphylactic transfusion reaction
  • Shock co-occurrent and due to anaphylaxis caused by serum

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Complications following infusion, transfusion and therapeutic injection (T80). 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 T80.59XA: its own notes plus those printed at T80.5, T80, block T80-T88, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From T80 Complications following infusion, transfusion and therapeutic injection applies to 114 codes
  • complications following perfusion

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From T80.5 Anaphylactic reaction due to serum applies to 9 codes
  • ABO incompatibility reaction due to transfusion of blood or blood products (T80.3-)
  • allergic reaction or shock NOS (T78.2)
  • anaphylactic reaction or shock NOS (T78.2)
  • anaphylactic reaction or shock due to adverse effect of correct medicinal substance properly administered (T88.6)
  • other serum reaction (T80.6-)

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.

From T80 Complications following infusion, transfusion and therapeutic injection applies to 114 codes
  • bone marrow transplant rejection (T86.01)
  • febrile nonhemolytic transfusion reaction (R50.84)
  • fluid overload due to transfusion (E87.71)
  • posttransfusion purpura (D69.51)
  • transfusion associated circulatory overload (TACO) (E87.71)
  • transfusion (red blood cell) associated hemochromatosis (E83.111)
  • transfusion related acute lung injury (TRALI) (J95.84)
From Block T80-T88 Complications of surgical and medical care, not elsewhere classified applies to 1,683 codes
  • any encounters with medical care for postprocedural conditions in which no complications are present, such as:
  • artificial opening status (Z93.-)
  • closure of external stoma (Z43.-)
  • fitting and adjustment of external prosthetic device (Z44.-)
  • burns and corrosions from local applications and irradiation (T20-T32)
  • complications of surgical procedures during pregnancy, childbirth and the puerperium (O00-O9A)
  • mechanical complication of respirator [ventilator] (J95.850)
  • poisoning and toxic effects of drugs and chemicals (T36-T65 with fifth or sixth character 1-4 or 6)
  • postprocedural fever (R50.82)
  • specified complications classified elsewhere, such as:
  • cerebrospinal fluid leak from spinal puncture (G97.0)
  • colostomy malfunction (K94.0-)
  • disorders of fluid and electrolyte imbalance (E86-E87)
  • functional disturbances following cardiac surgery (I97.0-I97.1)
  • intraoperative and postprocedural complications of specified body systems (D78.-, E36.-, E89.-, G97.3-, G97.4, H59.3-, H59.-, H95.2-, H95.3, I97.4-, I97.5, J95.6-, J95.7, K91.6-, L76.-, M96.-, N99.-)
  • ostomy complications (J95.0-, K94.-, N99.5-)
  • postgastric surgery syndromes (K91.1)
  • postlaminectomy syndrome NEC (M96.1)
  • postmastectomy lymphedema syndrome (I97.2)
  • postsurgical blind-loop syndrome (K91.2)
  • ventilator associated pneumonia (J95.851)
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Block T80-T88 Complications of surgical and medical care, not elsewhere classified applies to 1,683 codes
  • code for adverse effect, if applicable, to identify drug (T36-T50 with fifth or sixth character 5)
  • code(s) to identify the specified condition resulting from the complication
  • code to identify devices involved and details of circumstances (Y62-Y82)
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Notes

General instructions on how these codes are used.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • 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.

From T80 Complications following infusion, transfusion and therapeutic injection applies to 114 codes
  • The appropriate 7th character is to be added to each code from category T80
Values for category T80 Encounter: Initial, Subsequent, Sequela
  • 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 T80.59XA, its category, or a range that includes it.

Excludes1 5

These codes carry an Excludes1 note naming T80.59XA: they are not reported together with it, unless the two conditions are unrelated.

  • R57 Shock, not elsewhere classified
    anaphylactic shock due to serum (T80.5-) names T80.5-, which includes this code
  • T78.2 Anaphylactic shock, unspecified
    anaphylactic reaction or shock due to serum (T80.5-) names T80.5-, which includes this code
  • T79.4 Traumatic shock
    anaphylactic shock due to serum (T80.5-) names T80.5-, which includes this code
  • T81.1 Postprocedural shock
    anaphylactic shock due to serum (T80.5-) names T80.5-, which includes this code
  • T88.6 Anaphylactic reaction due to adverse effect of correct drug or medicament properly administered
    anaphylactic reaction due to serum (T80.5-) names T80.5-, which includes this code

Excludes2 4

These codes carry an Excludes2 note naming T80.59XA: its condition is not part of those codes, and both may be reported when the patient has both.

  • T45.8 Poisoning by, adverse effect of and underdosing of other primarily systemic and hematological agents
    transfusion reactions (T80.-) names T80.-, which includes this code
  • T81 Complications of procedures, not elsewhere classified
    complications following infusion, transfusion and therapeutic injection (T80.-) names T80.-, which includes this code
  • T88 Other complications of surgical and medical care, not elsewhere classified
    complication following infusion, transfusion and therapeutic injection (T80.-) names T80.-, which includes this code
  • T88.1 Other complications following immunization, not elsewhere classified
    anaphylactic shock due to serum (T80.5-) names T80.5-, which includes this code

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INJ037
Complication of other surgical or medical care, injury, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

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 T80.59XA to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
999.49 Anaph react d/t ot serum
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About T80.59XAOverview

What is the ICD-10 code for anaphylactic reaction due to other serum, initial encounter?

The ICD-10-CM code for anaphylactic reaction due to other serum, initial encounter is T80.59XA (sometimes written as T8059XA). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is T80.59XA (Anaphylactic reaction due to other serum) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report anaphylactic reaction due to other serum, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in T80.59XA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for anaphylactic reaction due to other serum, such as an emergency visit or first evaluation.

What MS-DRG does T80.59XA group to?

When anaphylactic reaction due to other serum, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 915, 916, with relative weights from 0.6926 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.

Is T80.59XA a CC or MCC?

CMS lists T80.59XA as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 6 closely related codes in its exclusion list.