2026 ICD-10-CM Diagnosis Code T63.301AToxic effect of unspecified spider venom, accidental (unintentional), initial encounter
T63.301A is a billable ICD-10-CM diagnosis code for toxic effect of unspecified spider venom, accidental (unintentional), 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 myelopathy caused by spider venom. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: bites; initial encounter; External cause codes: intent of injury, accidental/unintentional; and Toxic effects, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Myelopathy caused by spider venom
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Toxic effect of contact with venomous animals and plants (T63). 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
Spider Bites
Though many people are afraid of spiders, they rarely bite people unless threatened. Most spider bites are harmless. Occasionally, spider bites can cause allergic reactions. And bites by the venomous black widow and brown recluse spiders can be very dangerous to people.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T63.301A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T63.301AOverview
Is T63.301A a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of unspecified spider venom, accidental (unintentional), initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T63.301A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for toxic effect of unspecified spider venom, accidental (unintentional), such as an emergency visit or first evaluation.
What MS-DRG does T63.301A group to?
When toxic effect of unspecified spider venom, accidental (unintentional), 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 T63.301A?
Under the General Equivalence Mappings, toxic effect of unspecified spider venom, accidental (unintentional), initial encounter converts to ICD-9-CM 989.5 (toxic effect venom) and E905.1 (venomous spider bite). 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.
