New for FY2027 ICD-10-CM · October 1, 2026
T65.851A: Toxic effect of medetomidine, accidental (unintentional), initial encounter
By the HCC Buddy Coding Team
The official ICD-10-CM descriptor is Toxic effect of medetomidine, accidental (unintentional), initial encounter. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.
Billable code. Verified against the official FY2027 order file.
FY2027 Tabular instructions
Instructions below include applicable chapter, section and parent-code notes. Each note identifies where it appears in the official source.
Instructional note
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
Source: S00-T88 (chapter, inherited).
Instructional note
code to identify any retained foreign body, if applicable (Z18.-)
Source: S00-T88 (chapter, inherited).
Excludes2
birth trauma (P10-P15)
Source: S00-T88 (chapter, inherited).
Excludes2
obstetric trauma (O70-O71)
Source: S00-T88 (chapter, inherited).
Instructional note
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.
Source: S00-T88 (chapter, inherited).
Instructional note
When no intent is indicated code to accidental. Undetermined intent is only for use when there is specific documentation in the record that the intent of the toxic effect cannot be determined.
Source: T51-T65 (section, inherited).
Instructional note
code(s):
Source: T51-T65 (section, inherited).
Instructional note
for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)
Source: T51-T65 (section, inherited).
Instructional note
personal history of foreign body fully removed (Z87.821)
Source: T51-T65 (section, inherited).
Instructional note
to identify any retained foreign body, if applicable (Z18.-)
Source: T51-T65 (section, inherited).
Excludes1
contact with and (suspected) exposure to toxic substances (Z77.-)
Source: T51-T65 (section, inherited).
Seventh-character instruction
The appropriate 7th character is to be added to each code from category T65
Source: T65 (category, inherited).
Instructional note
initial encounter
Source: T65 (category, inherited).
Instructional note
subsequent encounter
Source: T65 (category, inherited).
Instructional note
sequela
Source: T65 (category, inherited).
Instructional note
code to identify associated manifestations, such as:
Source: T65.85 (self, inherited).
Instructional note
bradycardia NOS (R00.1)
Source: T65.85 (self, inherited).
Instructional note
somnolence, stupor and coma (R40.-)
Source: T65.85 (self, inherited).
Instructional note
Toxic effect of medetomidine NOS
Source: T65.851 (self, inherited).
Seventh-character definitions
- A: initial encounter
- D: subsequent encounter
- S: sequela
Compare the FY2027 additions, removals and billable-status changes
What does T65.851A mean in FY2027?
The official ICD-10-CM descriptor is Toxic effect of medetomidine, accidental (unintentional), initial encounter. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.
When did T65.851A become an ICD-10-CM code?
T65.851A is new for FY2027 ICD-10-CM, effective October 1, 2026. It is absent from the FY2026 April order file. Use the code set that applies to the encounter or inpatient discharge date, and check the official Tabular instructions.
Is T65.851A billable in FY2027?
The FY2027 order file marks T65.851A as billable. Check the complete Tabular instructions and documentation before assigning it.
Does T65.851A map to an HCC?
T65.851A is not in the current CMS mapping file (it is new for FY2027), and CMS has not yet published payment year 2028 mappings. No HCC category or RAF coefficient is shown.
Source: CMS FY2027 ICD-10-CM order file. Payment model: CMS CY 2027 Rate Announcement. Read the FY2027 Official Guidelines.