U.S. ICD-10-CM · FY 2027

T66 ICD-10-CM Code: Radiation sickness, unspecified

A clear reference for the official code description, hierarchy, and related coding information from the FY 2027 U.S. release.

Code definition

Official description

T66

Radiation sickness, unspecified

ICD-10-CM diagnosis code · United States clinical modification

Classification

Where T66 sits

  1. 1

    Chapter 19

    Injury, poisoning and certain other consequences of external causes (S00-T88)

  2. 2

    Section

    Other and unspecified effects of external causes (T66-T78)

  3. 3

    Category T66

    Radiation sickness, unspecified

  4. 4

    Code T66

    Radiation sickness, unspecified

More specific choices

Codes under T66

T66 is a non-billable category. Choose the child code that best matches the documented diagnosis.

Documentation details

Notes for this code

Inclusion terms

No inclusion terms are listed for T66.

Code first

No “code first” instruction is listed for T66.

Use additional code

No “use additional code” instruction is listed for T66.

Excludes1

Conditions that should not be reported together with this code.

  • specified adverse effects of radiation, such as:
  • burns (T20-T31)
  • leukemia (C91-C95)
  • radiation gastroenteritis and colitis (K52.0)
  • radiation pneumonitis (J70.0)
  • radiation related disorders of the skin and subcutaneous tissue (L55-L59)
  • sunburn (L55.-)

Excludes2

Conditions not included here that may be reported separately when present.

No Excludes2 note is listed for T66.

Transparency

Source and release

Data release

U.S. ICD-10-CM · FY 2027

Effective date

Oct 1, 2026

This reference is generated from Vero’s ICD-10-CM description, hierarchy, and code-note dataset. The visible content and structured data share that source.

Review the CDC/NCHS ICD-10-CM source

Code-specific guidance

Frequently asked questions

What does ICD-10-CM code T66 mean?

T66 is the FY 2027 U.S. ICD-10-CM code for “Radiation sickness, unspecified.”

Is T66 a billable or specific ICD-10-CM code?

No. T66 has more specific child codes in the FY 2027 reference data. Select the code that matches the documentation and confirm the active code set and payer requirements.

Where is T66 located in ICD-10-CM?

T66 is listed in Chapter 19, Injury, poisoning and certain other consequences of external causes (S00-T88), within Other and unspecified effects of external causes (T66-T78) (T66–T78), under category T66, Radiation sickness, unspecified.

What coding notes are listed for T66?

No inclusion terms are listed for T66 in this reference record. No code-first instruction is listed. Excludes1 notes: specified adverse effects of radiation, such as:; burns (T20-T31); leukemia (C91-C95); radiation gastroenteritis and colitis (K52.0); radiation pneumonitis (J70.0); radiation related disorders of the skin and subcutaneous tissue (L55-L59); sunburn (L55.-). No Excludes2 note is listed.

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