2026 ICD-10-CM Diagnosis Code T61.8X4SToxic effect of other seafood, undetermined, sequela
T61.8X4S is a billable ICD-10-CM diagnosis code for toxic effect of other seafood, undetermined, sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 922 through 923. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Poisoning/toxic effect/adverse effects/underdosing, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
T61.8X4S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
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.
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 T61.8X4S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T61.8X4SOverview
Is T61.8X4S (Toxic effect of other seafood, undetermined) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of other seafood, undetermined, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T61.8X4S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the toxic effect of other seafood, undetermined itself has resolved, not the original event.
What MS-DRG does T61.8X4S group to?
When toxic effect of other seafood, undetermined, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T61.8X4S exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for toxic effect of other seafood, undetermined, sequela on inpatient claims.
What is the ICD-9 equivalent of T61.8X4S?
Under the General Equivalence Mappings, toxic effect of other seafood, undetermined, sequela converts to ICD-9-CM 909.1 (late eff nonmed substanc) and E989 (late eff inj-undet circ). 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.
