T56.91XD
Toxic effect of unspecified metal, accidental (unintentional), subsequent encounter
T56.91XD (also written T5691XD) is a billable ICD-10-CM diagnosis code for toxic effect of unspecified metal, accidental (unintentional), subsequent encounter. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 144 codes in category T56 (Toxic effect of metals). Its 7th character, D, means subsequent encounter. Its coding notes include a Use additional code instruction, 3 Excludes1 entries and 2 Excludes2 entries.
7th character
Category T56 requires a 7th character. T56.91 has only 5 characters, so a placeholder X fills the 6th position.
Guidelines tips
From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.
The 7th character depends on whether the patient is in active treatment, not on who sees the patient. An aftercare Z code is not used for injury aftercare.
T36-T65 codes already include the substance and the intent, so no additional external cause code is required. Do not code directly from the Table of Drugs and Chemicals.
Use additional code
Add the listed code as a secondary code, if known.
Also from chapter/block level (5 notes)
- code to identify any retained foreign body, if applicable (Z18.-)
Excludes1
Not coded here. The listed conditions generally should not be reported together.
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (2 notes)
- birth trauma (P10-P15)
- obstetric trauma (O70-O71)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Home Health Primary
Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the MMTA - Other clinical group.
Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026Includes
Further defines or gives examples of the content of the category.
- toxic effects of fumes and vapors of metals
- toxic effects of metals from all sources, except medicinal substances
Notes
Also from chapter/block level (3 notes)
- 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.
- 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.