DxCodebookFY2027 · Oct 1, 2026 – Sep 30, 2027

Category · FY2027

T66 Radiation sickness, unspecified

  • Header · not billable
  • Codes take a 7th character

T66 is not billable. The category heads 3 billable codes in FY2027. Its codes take a 7th character, so none is complete with fewer than 7 characters.

Index → code

  • Irradiation effects, adverse → T66
  • Sicknessradiation → T66
  • Radiationeffects NOS → T66

Where it sits

  1. Chapter 19 Injury, poisoning and certain other consequences of external causes (S00-T88)
  2. T66-T78 Other and unspecified effects of external causes (T66-T78)
  3. T66 Radiation sickness, unspecified
Billable codes
3
Subdivisions
0
CC / MCC codes
0 / 0
HCC V28 codes
0
New FY2027
0
Index entries
7

Codes in T66

  1. T66.XXXA
    Radiation sickness, unspecified, initial encounter
    Billable
  2. T66.XXXD
    Radiation sickness, unspecified, subsequent encounter
    BillableExempt
  3. T66.XXXS
    Radiation sickness, unspecified, sequela
    BillableExempt

Sources of each column. Rows marked +7th need a 7th character: pick one to build the full code; its code card has its own flags.

Instructions

At T66

Excludes1

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

Notes that also apply

Block T66-T78 instructions (Code also 6): printed on the block page.

Chapter 19 instructions (Notes 2, Excludes2 2, Use additional code 1): printed on the chapter 19 page.

7th characters

7th characters for T66 defined here

The appropriate 7th character is to be added to code T66

7th characters for T66
7thMeaning (NCHS)
Ainitial encounter
Dsubsequent encounter
Ssequela

A code that takes a 7th character is invalid without it; the placeholder X fills a code shorter than 6 characters (Official Guidelines I.A.5). How 7th characters work.

Index entries

  • Irradiation effects, adverse → T66
  • Effect, adverseinfrared (radiation) (rays) NOS → T66
  • Effect, adverseradiation (diagnostic) (infrared) (natural source) (therapeutic) (ultraviolet) (X-ray) NOS → T66
  • Effect, adverseultraviolet (radiation) (rays) NOS → T66
  • Radiationeffects NOS → T66
  • Radiationsickness NOS → T66
  • Sicknessradiation → T66

NCHS Alphabetic Index. Index first, then the Tabular List.

Hierarchy