Skip to main content

Z77 vs Z91.13

Z77 (Other contact with and (suspected) exposures hazardous to health) compared with Z91.13 (Patient's unintentional underdosing of medication regimen), from the official CMS tabular data.

Summary

These codes can be reported together when both conditions are documented, because Z91.13 lists Z77 under Excludes2, which marks them as distinct conditions.

Official rule
What is different?

The conditions named.Z77 is “Other contact with and (suspected) exposures hazardous to health”; Z91.13 is “Patient's unintentional underdosing of medication regimen”.

Registry fact

Can these codes be reported together?

Yes, when both are documented.Z91.13 lists Z77 under Excludes2: “contact with and (suspected) exposures hazardous to health (Z77.-)”. 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.

Official rule

Is there an Excludes2 relationship?

Yes.Z91.13’s tabular entry: “contact with and (suspected) exposures hazardous to health (Z77.-)”. The note covers Z77.

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

Z91.13
Patient's unintentional underdosing of medication regimen
↔
Z77
Other contact with and (suspected) exposures hazardous to health

What we found

Yes, when both are documented.Z91.13 carries an Excludes2 note covering Z77: “contact with and (suspected) exposures hazardous to health (Z77.-)”

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 FY2026

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

Z77Other contact with and (suspected) exposures hazardous to healthZ91.13Patient's unintentional underdosing of medication regimen
Billing statusNon-billable header

Report instead: Z77.010, Z77.011, Z77.012, Z77.013, Z77.018

Non-billable header

Report instead: Z91.130, Z91.138

ClassificationZ00-Z99 — Factors Influencing Health Status and Contact with Health Services (Z00-Z99)Z00-Z99 — Factors Influencing Health Status and Contact with Health Services (Z00-Z99)
DefinitionOther contact with and (suspected) exposures hazardous to health is a non-billable ICD-10-CM category code (Z77).Patient's unintentional underdosing of medication regimen is a non-billable ICD-10-CM category code (Z91.13).
Includes
contact with and (suspected) exposures to potential hazards to health
—
Excludes2
contact with and (suspected) exposure to communicable diseases (Z20.-)
exposure to (parental) (environmental) tobacco smoke in the perinatal period (P96.81)
newborn affected by noxious substances transmitted via placenta or breast milk (P04.-)
occupational exposure to risk factors (Z57.-)
retained foreign body (Z18.-)
retained foreign body fully removed (Z87.821)
toxic effects of substances chiefly nonmedicinal as to source (T51-T65)
caregiver noncompliance with patient's medical treatment and regimen (Z91.A-)
contact with and (suspected) exposures hazardous to health (Z77.-)
exposure to pollution and other problems related to physical environment (Z77.1-)
female genital mutilation status (N90.81-)
occupational exposure to risk factors (Z57.-)
personal history of physical injury and trauma (Z87.81, Z87.82-)
Code first—
underdosing of medication (T36-T50) with fifth or sixth character 6
Code also
any follow-up examination (Z08-Z09)
, if applicable, to identify underdosing of specific drug (T36-T50 with final character 6)
any follow-up examination (Z08-Z09)

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.

Edit this comparisonCheck a whole claim

Derived from the official CMS ICD-10-CM tabular data (FY2026). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources