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Z16.21 ICD-10-CM Code: Resistance to vancomycin

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
3 Excludes1 · 1 code-first instruction

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 867 — OTHER INFECTIOUS AND PARASITIC DISEASES DIAGNOSES WITH MCC (MDC 18)
  • MS-DRG 868 — OTHER INFECTIOUS AND PARASITIC DISEASES DIAGNOSES WITH CC (MDC 18)
  • MS-DRG 869 — OTHER INFECTIOUS AND PARASITIC DISEASES DIAGNOSES WITHOUT CC/MCC (MDC 18)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for Z16.21 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on Z16.21 itself; “inherited from” names the category or block whose note applies here.

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Source: inherited from Z16

Code First

Underlying conditions that must be sequenced before this code.

  • the infection

Source: inherited from Z16

Coder workflow for Z16.21

MedCoder structured workflow — derived from this code’s own official record

Before you code Z16.21

  1. Confirm the reason for the encounter this Z code records: the circumstance it records. Check whether the code may be reported as first-listed or principal — some Z codes are limited to one position — and do not report a history or status code for a condition documented as current. Z code categories and their reporting positions (Guidelines I.C.21.c, I.C.21.c.15).

    Guide: Z codes as principal or first-listed diagnosis →

  2. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with Z16.21. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support a condition named in Z16.21’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewA49.02, J15.212, A41.02

  2. Is the underlying (etiologic) condition the Code First note names documented?
    Yes → Sequence the underlying condition first, then Z16.21.
    No → Continue; do not add an underlying condition the record does not document.

Consider Z16.21. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
The underlying (etiologic) condition
Named in the Code First note; sequenced before this code when documented (Guidelines I.A.13).
The reason for the encounter
Whether the code records the encounter’s purpose, a status, or a history — and whether it may be first-listed (Guidelines I.C.21.c).

Official instructions as workflow

  • Excludes1 — check before selecting Z16.21(3 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with Z16.21: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareA49.02, J15.212, A41.02

    See the official tabular notes · Guidelines I.A.12.a

  • Code First — sequencing check(1 note)

    Coding workflow: Check whether the underlying or etiologic condition the note names is documented. When it is, sequence it before Z16.21. Do not add an underlying condition the record does not document.

    See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: Both the condition Z16.21 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewA49.02, J15.212, A41.02

Documentation: The underlying condition the Code First note names is documented alongside this condition.

Coding question: How are the two sequenced?

Path: Review the Code First note.

Reason: The underlying condition is sequenced first and the manifestation follows (Guidelines I.A.13).

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Code Overview

Resistance to vancomycin is a billable ICD-10-CM diagnosis code (Z16.21).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (1)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Official Coding Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Official source data — quoted verbatim from the CMS/NCHS Official Guidelines

Verbatim excerpts from the ICD-10-CM Official Guidelines for Coding and Reporting (CMS/NCHS) that govern this code.

Chapter 1: Certain Infectious and Parasitic Diseases (A00-B99), U07.1, U09.9 a. Human Immunodeficiency Virus (HIV) Infections 1) Code only confirmed cases

c. Infections resistant to antibiotics Many bacterial infections are resistant to current antibiotics. It is necessary to identify all infections documented as antibiotic resistant. Assign a code from category Z16, Resistance to antimicrobial drugs, following the infection code only if the infection code does not identify drug resistance.

Chapter 21: Factors influencing health status and contact with health services (Z00-Z99)

Codes from category Z15 should generally not be used as principal or first-listed codes. If the patient has the condition to which he/she is susceptible, and that condition is the reason for the encounter, the code for the current condition should be sequenced first. If the patient is being seen for follow-up after completed treatment for this condition, and the condition no longer exists, a follow-up code should be sequenced first, followed by the appropriate personal history and genetic susceptibility codes. If the purpose of the encounter is genetic counseling associated with procreative management, code Z31.5, Encounter for genetic counseling, should be assigned as the first-listed code, followed by a code from category Z15. Additional codes should be assigned for any applicable family or personal history. Z16 Resistance to antimicrobial drugs This category indicates that a patient has a condition that is resistant to antimicrobial drug treatment. Sequence the infection code first. Z17 Estrogen, and other hormones and factors receptor status Z18 Retained foreign body fragments Z19 Hormone sensitivity malignancy status Z21 Asymptomatic HIV infection status This code indicates that a patient has tested positive for HIV but has manifested no signs or symptoms of the disease. Z22 Carrier of infectious disease Carrier status indicates that a person harbors the specific organisms of a disease without manifest symptoms and is capable of transmitting the infection. Z28.3 Underimmunization status

Verify Before Coding

  • Principal-diagnosis restriction. The Medicare Code Editor lists this code as unacceptable as a principal diagnosis: it describes a circumstance influencing health status rather than a current illness or injury being treated. It is valid as a secondary diagnosis.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name Z16.21 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: Z16.3 — Resistance to other antimicrobial drugs (via Z16.2.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 11 Use Additional Code instructions: J09 — Influenza due to certain identified influenza viruses (via Z16.-), J09-J18 — Influenza and pneumonia (J09-J18) (via Z16.-), J10 — Influenza due to other identified influenza virus (via Z16.-), J11 — Influenza due to unidentified influenza virus (via Z16.-), J12 — Viral pneumonia, not elsewhere classified (via Z16.-), J13 — Pneumonia due to Streptococcus pneumoniae (via Z16.-), J14 — Pneumonia due to Hemophilus influenzae (via Z16.-), J15 — Bacterial pneumonia, not elsewhere classified (via Z16.-), J16 — Pneumonia due to other infectious organisms, not elsewhere classified (via Z16.-), J17 — Pneumonia in diseases classified elsewhere (via Z16.-), J18 — Pneumonia, unspecified organism (via Z16.-).

These codes instruct coders to additionally report this code when it applies.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 3 MS-DRGs: DRG 867 (MDC 18), DRG 868 (MDC 18), DRG 869 (MDC 18).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):FAC015 — Resistance to antimicrobial drugs (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Principal diagnosis restriction (Medicare Code Editor)

Not acceptable as a principal diagnosis on an inpatient claim.

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Resistance to antimicrobial drugs).

Z16.10 — Resistance to unspecified beta lactam antibiotics, Z16.11 — Resistance to penicillins, Z16.12 — Extended spectrum beta lactamase (ESBL) resistance, Z16.13 — Resistance to carbapenem, Z16.19 — Resistance to other specified beta lactam antibiotics, Z16.20 — Resistance to unspecified antibiotic, Z16.22 — Resistance to vancomycin related antibiotics, Z16.23 — Resistance to quinolones and fluoroquinolones, Z16.24 — Resistance to multiple antibiotics, Z16.29 — Resistance to other single specified antibiotic, Z16.30 — Resistance to unspecified antimicrobial drugs, Z16.31 — Resistance to antiparasitic drug(s), Z16.32 — Resistance to antifungal drug(s), Z16.33 — Resistance to antiviral drug(s), Z16.341 — Resistance to single antimycobacterial drug, Z16.342 — Resistance to multiple antimycobacterial drugs, Z16.35 — Resistance to multiple antimicrobial drugs, Z16.39 — Resistance to other specified antimicrobial drug

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Resistance, resistant”; these codes share that main term but sit in a different category of the Tabular List.

D68.51 — Activated protein C resistance (activated protein C), E07.89 — Other specified disorders of thyroid (thyroid hormone), E88.818 — Other insulin resistance (insulin, specified type NEC), E88.819 — Insulin resistance, unspecified (insulin), O26.89 — Other specified pregnancy related conditions (insulin, complicating pregnancy)

Contextual Map

Every relationship of Z16.21 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run Z16.21 with these 9 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Use Additional Code instructions (11)

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 18 — Infectious and Parasitic Diseases, Systemic or Unspecified Sites[MDC crossing]: “Infectious and Parasitic Diseases, Systemic or Unspecified Sites — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs. 1 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

  • Resistance, resistant (to), organism (s), to, drug, vancomycin[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (23)

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Coding guidelines Official source data
ICD-10-CM Official Guidelines for Coding and Reporting (FY2026), quoted by section Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "Z16.21 — Resistance to vancomycin." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/z16.21-resistance-to-vancomycin

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Resistance to vancomycin

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to Z16.21 in its code family, with their registry titles.

View all codes in the Z16 family