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F55 vs T36.AX4

F55 (Abuse of non-psychoactive substances) compared with T36.AX4 (Poisoning by fluoroquinolone antibiotics, undetermined), from the official CMS tabular data.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Summary

These codes can be reported together when both conditions are documented, because T36.AX4 lists F55 under Excludes2, which marks them as distinct conditions.

Official rule
What is different?

The conditions named and chapter.F55 is “Abuse of non-psychoactive substances”; T36.AX4 is “Poisoning by fluoroquinolone antibiotics, undetermined”. F55 sits in F01-F99 — Mental, Behavioral and Neurodevelopmental Disorders (F01-F99); T36.AX4 in S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88).

Registry fact

Can these codes be reported together?

Yes, when both are documented.T36.AX4 lists F55 under Excludes2: “abuse of non-dependence-producing substances (F55.-)”. Excludes2 marks distinct conditions that may both be reported when both are documented.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes1 relationship?

None.Neither entry carries an Excludes1 note that names the other code. T36.AX4 carries 5 Excludes1 notes covering other codes; the side-by-side table quotes them.

Official rule

Is there an Excludes2 relationship?

Yes.T36.AX4’s tabular entry: “abuse of non-dependence-producing substances (F55.-)”. The note covers F55.

Official ruleGuide: Excludes1 vs Excludes2

Is one more specific?

Not comparable.The codes sit in different categories; specificity is only comparable within one category.

Is one a parent or header code?

Both are headers.Both are non-billable headers, and neither contains the other.

Registry fact

Are there sequencing instructions?

None.Neither entry carries a Code First or Use Additional Code note that names the other.

Official rule

Are there other coding relationships?

None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.

MedCoder-derived

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels

Can these codes be reported together?

Informational

Excludes2 relationship

T36.AX4
Poisoning by fluoroquinolone antibiotics, undetermined
↔
F55
Abuse of non-psychoactive substances

What we found

Yes, when both are documented.T36.AX4 carries an Excludes2 note covering F55: “abuse of non-dependence-producing substances (F55.-)”

Excludes2 marks distinct conditions — both may be reported when both are documented.

What to review

Report both only when the documentation supports both conditions; otherwise report the one documented.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes2 note means the excluded condition is not part of the code above it, but a patient can have both. Report both when both are documented.

Source / rule

CMS ICD-10-CM tabular instructional notes

Official guidance behind these answers

  • Section I.A.12.b — Excludes2 · applies to: Excludes2

    A type 2 Excludes note represents “Not included here.” An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.

    ICD-10-CM Official Guidelines FY2027

Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum

Side by side

Similar descriptions do not make codes interchangeable. The documentation and the official instructions decide which code applies.

Official descriptionDiffers
F55

Abuse of non-psychoactive substances

T36.AX4

Poisoning by fluoroquinolone antibiotics, undetermined

StatusDiffers
F55
Non-billable header

A header is not reported on a claim; a code beneath it is.

Report instead: F55.0, F55.1, F55.2, F55.3, F55.4

T36.AX4
Non-billable header

A header is not reported on a claim; a code beneath it is.

Report instead: T36.AX4A, T36.AX4D, T36.AX4S

Excludes1Differs
F55

None at this code

T36.AX4
  • antineoplastic antibiotics (T45.1-)
  • locally applied antibiotic NEC (T49.0)
  • topically used antibiotic for ear, nose and throat (T49.6)
  • topically used antibiotic for eye (T49.5)
  • toxic reaction to local anesthesia in pregnancy (O29.3-)
Excludes2Differs
F55
  • abuse of psychoactive substances (F10-F19)
T36.AX4
  • abuse and dependence of psychoactive substances (F10-F19)
  • abuse of non-dependence-producing substances (F55.-)
  • immunodeficiency due to drugs (D84.821)
  • drug reaction and poisoning affecting newborn (P00-P96)
  • pathological drug intoxication (inebriation) (F10-F19)
Code firstDiffers
F55

None at this code

T36.AX4
  • , for adverse effects, the nature of the adverse effect, such as:
  • adverse effect NOS (T88.7)
Use additional codeDiffers
F55

None at this code

T36.AX4
  • code(s) to specify:
  • manifestations of poisoning
  • underdosing or failure in dosage during medical and surgical care (Y63.6, Y63.8-Y63.9)
CategoryDiffers
F55

Is itself a category

T36.AX4

T36 Poisoning by, adverse effect of and underdosing of systemic antibiotics

ChapterDiffers
F55

F01-F99 — Mental, Behavioral and Neurodevelopmental Disorders (F01-F99)

T36.AX4

S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88)

IncludesDiffers
F55

None at this code

T36.AX4
  • adverse effect of correct substance properly administered
  • poisoning by overdose of substance
  • poisoning by wrong substance given or taken in error
  • underdosing by (inadvertently) (deliberately) taking less substance than prescribed or instructed
7th characterDiffers
F55

None at this code

T36.AX4
  • The appropriate 7th character is to be added to each code from category T36

No Code also note at either code.

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on. In a row that differs, notes every code shares are dimmed.

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Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources