2026 ICD-10-CM Diagnosis Code T61.774AOther fish poisoning, undetermined, initial encounter
T61.774A is a billable ICD-10-CM diagnosis code for other fish poisoning, undetermined, 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 917 through 918. Coders also document this condition as haff syndrome. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, undetermined; External cause codes: poisoning by non-drug; and Toxic effects, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Haff syndrome
- Myoglobinuria
- Myoglobinuria following ingestion of eel
- Pelagic paralysis
- Toxic neuromuscular junction disorder
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Toxic effect of noxious substances eaten as seafood (T61). 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
Myoglobinuria
the presence of myoglobin in urine usually as a result of rhabdomyolysis.Myoglobinuria
the presence of myoglobin in the urine.
Table of Drugs and ChemicalsClinical
Patient EducationClinical
Foodborne Illness
Each year, around 48 million people in the United States get sick from contaminated food. Common causes include bacteria and viruses. Less often, the cause may be a parasite or a harmful chemical, such as a high amount of pesticides. Symptoms of foodborne illness depend on the cause. They can be mild or serious. They usually include:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T61.774A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T61.774AOverview
Is T61.774A (Other fish poisoning, undetermined) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other fish poisoning, undetermined, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T61.774A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for other fish poisoning, undetermined, such as an emergency visit or first evaluation.
What MS-DRG does T61.774A group to?
When other fish poisoning, undetermined, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of T61.774A?
Under the General Equivalence Mappings, other fish poisoning, undetermined, initial encounter converts to ICD-9-CM 988.0 (toxic eff fish/shellfish) and E980.9 (undeter pois-sol/liq NEC). 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.
