T66 ICD-10-CA code: Unspecified effects of radiation

T66 is the ICD-10-CA code for “Unspecified effects of radiation” in CIHI’s FY 2026–2027 release, in effect from Apr 1, 2026.

Official description

T66

Unspecified effects of radiation

ICD-10-CA · Canada

Index terms

Entries in CIHI’s alphabetical index that lead to T66. Searching the index by the condition the note names is how coders reach this code.

  • Radionecrosis NEC
  • Reaction, Xray NEC
  • Reaction, radiation NEC
  • Sickness, radiation NEC
  • Reaction, ultraviolet NEC
  • Radium, adverse effect NEC
  • Reaction, postradiation NEC
  • Effect, adverse NEC, Xrays NEC
  • Effect, adverse NEC, radium NEC
  • Teletherapy, adverse effect NEC
  • Xray (of), effects, adverse NEC
  • Effect, adverse NEC, uranium NEC
  • Irradiation effects, adverse NEC
  • Roentgen ray, adverse effect NEC
  • Effect, adverse NEC, polonium NEC
  • Lesion (nontraumatic), radium NEC
  • Radiation, effects or sickness NEC
  • Effect, adverse NEC, fluoroscopy NEC
  • Effect, adverse NEC, irradiation NEC
  • Effect, adverse NEC, mesothorium NEC
  • Effect, adverse NEC, teletherapy NEC
  • Lesion (nontraumatic), radiation NEC
  • Effect, adverse NEC, radiotherapy NEC
  • Effect, adverse NEC, radioactivity NEC
  • Effect, adverse NEC, cobalt, radioactive
  • Injury (specified injury type), Xray NEC
  • Fallout, radioactive (adverse effect) NEC
  • Lesion (nontraumatic), Xray (radiation) NEC
  • Radioactive substances, adverse effects NEC
  • Injury (specified injury type), radiation NEC
  • Effect, adverse NEC, fallout (radioactive) NEC
  • Effect, adverse NEC, isotope (radioactive) NEC
  • Effect, adverse NEC, radioactive substance NEC
  • Injury (specified injury type), infrared rays NEC
  • Effect, adverse NEC, infrared (radiation) (rays) NEC
  • Injury (specified injury type), ultraviolet rays NEC
  • Complication, complications (from) (of), radiation NEC
  • Effect, adverse NEC, ultraviolet (radiation) (rays) NEC
  • Misadventure (prophylactic) (therapeutic), radiation NEC
  • Complication, complications (from) (of), radiotherapy NEC
  • Misadventure (prophylactic) (therapeutic), radiotherapy NEC
  • Effect, adverse NEC, implantation (removable) of isotope or radium NEC
  • Effect, adverse NEC, roentgen rays, roentgenography, roentgenoscopy NEC
  • Effect, adverse NEC, ingestion or injection of isotope (therapeutic) NEC
  • Effect, adverse NEC, radiation (diagnostic) (fallout) (infrared) (natural source) (therapeutic) (tracer) (ultraviolet) (Xray) NEC

Notes for T66

As CIHI prints them, with any note T66 takes from the headings above it.

Includes

  • Radiation sickness

Excludes

Conditions classified elsewhere.

  • Specified adverse effects of radiation, such as:• burns (T20-T31)• leukaemia (C91-C95)• radiation• gastroenteritis and colitis (K52.0)• pneumonitis (J70.0)• related disorders of the skin and subcutaneous tissue (L55-L59)• sunburn (L55.-)
  • Birth trauma (P10-P15)obstetric trauma (O70-O71)From Chapter 19: Injury, poisoning and certain other consequences of external causes (S00-T98)

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 multiple or unspecified body regions as well as poisoning and certain other consequences of external causes.Where multiple sites of injury are specified in the titles, the word "with" indicates involvement of both sites, and the word "and" indicates involvement of either or both sites.The principle of multiple coding of injuries should be followed wherever possible.Combination categories for multiple injuries is provided for use when there are insufficient detail as to the nature of the individual conditions, or for primary tabulation purposes when it is more convenient to record single code; otherwise, the component injuries should be coded separately.Reference should also be made to the coding rules and guidelines.The blocks of the S-section as well as (T00-T14 and T90-T98) contain injuries at the three-character level classified by type as follows:Superficial injury including:abrasionblister (nonthermal)contusion, including bruise and haematomainjury from superficial foreign body (splinter) without major open woundinsect bite (nonvenomous)Open wound including:animal bitecutlacerationpuncture wound:• NOS• with (penetrating) foreign bodyFracture including:Fracture:closed: comminuted, depressed, elevated, fissured, greenstick, impacted, linear, simple, slipped epiphysis, spiral — with or without delayed healingdislocateddisplacedFracture:open: compound, infected, missile, puncture, with foreign body — with or without delayed healingExcludes:malunion of fracture (M84.0)nonunion of fracture [pseudoarthrosis] (M84.1)pathological fracture (M84.4):• with osteoporosis (M80.-)stress fracture (M84.3)Dislocation, sprain and strain including:avulsion, laceration, sprain, strain, traumatic: haemarthosis, rupture, subluxation, tear of cartilage, joint (capsule), ligamentInjury to nerves and spinal cord including:complete or incomplete lesion of spinal cordlesion incontinuity of nerves and spinal cordtraumatic:• division of nerve• haematomyelia• paralysis (transient)• paraplegia• quadriplegiaInjury to blood vessels includingavulsion, cut, laceration, traumatic: aneurysm or fistula (arteriovenous), arterial haematoma, rupture of blood vesselsInjury of muscle, fascia and tendon including:avulsion, cut, laceration, strain, traumatic rupture of muscle, fascia and tendonCrushing InjuryTraumatic amputationInjury to internal organs including:blast injuries, bruise, concussion injuries, crushing, laceration, traumatic: haematoma, puncture, rupture, tear of internal organsOther and unspecified injuriesFrom Chapter 19: Injury, poisoning and certain other consequences of external causes (S00-T98)

Where T66 sits

  1. 1ChapterChapter 19: Injury, poisoning and certain other consequences of external causes (S00-T98)
  2. 2Block T66-T78Other and unspecified effects of external causes
  3. 3Valid code T66Unspecified effects of radiation

Source and release

Data release
ICD-10-CA · FY 2026–2027
Effective date
Apr 1, 2026
Publisher
CIHI

This page is built from the ICD-10-CA catalog that Vero Codes reads when it suggests codes: Canadian Institute for Health Information’s FY 2026–2027 release, imported from the publisher’s file and checked against it. The description, notes and structured data come from the same record.

Frequently asked questions

What does ICD-10-CA code T66 mean?

T66 is the ICD-10-CA code for “Unspecified effects of radiation” in CIHI’s ICD-10-CA FY 2026–2027 release.

Where is T66 in ICD-10-CA?

T66 sits under T66-T78 Other and unspecified effects of external causes, within Chapter 19: Injury, poisoning and certain other consequences of external causes (S00-T98).

What coding notes apply to T66?

ICD-10-CA lists Includes, Excludes, Note notes for T66, including those from the headings it sits under. They are listed on this page with where each one comes from.

Which ICD-10-CA release does this page use?

It uses CIHI’s FY 2026–2027 release, in effect from Apr 1, 2026 to Mar 31, 2027. It is a reference: confirm the code against the current list and the payer’s rules before you submit it.