I1A.0 ICD-10-CM Code: Resistant hypertension

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for I1A.0 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 I1A.0 itself; “inherited from” names the category or block whose note applies here.

Coder workflow for I1A.0

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

Before you code I1A.0

1. Check the record for heart involvement, chronic kidney disease, a documented cause, crisis, resistance, or pregnancy: each moves the case to a different category in I10–I16 and I1A, and the classification presumes the heart and kidney links unless the provider states they are unrelated. The hypertension guideline and the “with” convention (Guidelines I.C.9.a, I.A.15).

   Guide: The "with" convention →

2. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with I1A.0. 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 I1A.0’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.

   ReviewP29.2, I27.0

2. Is the underlying (etiologic) condition the Code First note names documented?
   Yes → Sequence the underlying condition first, then I1A.0.
   No → Continue; do not add an underlying condition the record does not document.

   ReviewI10, I15

Consider I1A.0. Then work the Use Additional Code note, and 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 conditions the Use Additional Code note names

Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.

Heart involvement, chronic kidney disease and its stage, cause, crisis, pregnancy

Each moves the case to a different hypertension category (Guidelines I.C.9.a).

Official instructions as workflow

• Excludes1 — check before selecting I1A.0(2 notes)

  Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with I1A.0: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

  CompareP29.2, I27.0

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

• Excludes2 — not part of I1A.0(1 note)

  Coding workflow: The conditions named in this note are not included in I1A.0. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

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

• Code First — sequencing check(3 notes)

  Coding workflow: Check whether the underlying or etiologic condition the note names is documented. When it is, sequence it before I1A.0. Do not add an underlying condition the record does not document.

  ReviewI10, I15

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

• Use Additional Code — after identifying I1A.0(6 notes)

  Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with I1A.0 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

  ReviewZ77.22, Z87.891, Z57.31, F17, Z72.0

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

Coding decision scenarios

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

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.

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.

• Hypertension, hypertensive (accelerated) (benign) (essential) (idiopathic) (malignant) (systemic), resistant (apparent treatment) (treatment) (true)

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.

Don’t confuse I1A.0 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of I1A.0 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• P29.2— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of neonatal hypertension moves the case to P29.2; the two are not reported together unless documented as unrelated.

  Full comparison: I1A.0 vs P29.2 →

• I27.0— Excludes1 conflict (Excludes1 — generally not reported together)

  Not coded here — the tabular list excludes this pair for the same encounter.

  Not reported together with this code, except where the two conditions are documented as unrelated.

  What moves you there: Documentation of primary pulmonary hypertension moves the case to I27.0; the two are not reported together unless documented as unrelated.

  Full comparison: I1A.0 vs I27.0 →

• O10— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of hypertensive disease complicating pregnancy, childbirth and the puerperium adds O10; it is not part of this code and both may be reported when both are documented.

  Full comparison: I1A.0 vs O10 →

• O11— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of hypertensive disease complicating pregnancy, childbirth and the puerperium adds O11; it is not part of this code and both may be reported when both are documented.

  Full comparison: I1A.0 vs O11 →

• O13— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of hypertensive disease complicating pregnancy, childbirth and the puerperium adds O13; it is not part of this code and both may be reported when both are documented.

  Full comparison: I1A.0 vs O13 →

• O16— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of hypertensive disease complicating pregnancy, childbirth and the puerperium adds O16; it is not part of this code and both may be reported when both are documented.

  Full comparison: I1A.0 vs O16 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Decision Points

The directives on this code's own record, as a pre-claim checklist.

1. Sequencing: 3 Code First instructions — the underlying condition is sequenced before this code when present. See the Code First notes
2. 6 Use Additional Code instructions — report the named additional code(s) when the documentation supports them. See the Use Additional Code notes
3. 2 Excludes1 entries — codes named there are generally not reported together with this code (Guidelines I.A.12.a). See the Excludes1 notes
4. 1 Excludes2 entry — those conditions are not part of this code and may be reported additionally when documented. See the Excludes2 notes

Checklist rows are derived from this code's own official directives; the wording of each check is MedCoder editorial. The official notes themselves are in the sections each row links to.

Verify Before Coding

• No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

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

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 2 MS-DRGs: DRG 304 (MDC 05), DRG 305 (MDC 05).

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

Clinical classification (AHRQ CCSR):CIR008 — Hypertension with complications and secondary hypertension (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

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Hypertension with complications and secondary hypertension).

I13.11 — Hypertensive heart and chronic kidney disease without heart failure, with stage 5 chronic kidney disease, or end stage renal disease, I13.2 — Hypertensive heart and chronic kidney disease with heart failure and with stage 5 chronic kidney disease, or end stage renal disease, I15.0 — Renovascular hypertension, I15.1 — Hypertension secondary to other renal disorders, I15.2 — Hypertension secondary to endocrine disorders, I15.8 — Other secondary hypertension, I15.9 — Secondary hypertension, unspecified, I16.0 — Hypertensive urgency, I16.1 — Hypertensive emergency, I16.9 — Hypertensive crisis, unspecified, I67.4 — Hypertensive encephalopathy, I97.3 — Postprocedural hypertension, O10.111 — Pre-existing hypertensive heart disease complicating pregnancy, first trimester, O10.112 — Pre-existing hypertensive heart disease complicating pregnancy, second trimester, O10.113 — Pre-existing hypertensive heart disease complicating pregnancy, third trimester, O10.119 — Pre-existing hypertensive heart disease complicating pregnancy, unspecified trimester, O10.12 — Pre-existing hypertensive heart disease complicating childbirth, O10.13 — Pre-existing hypertensive heart disease complicating the puerperium, O10.211 — Pre-existing hypertensive chronic kidney disease complicating pregnancy, first trimester, O10.212 — Pre-existing hypertensive chronic kidney disease complicating pregnancy, second trimester, +37 more

Same Index main term, other category

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

I13.11 — Hypertensive heart and chronic kidney disease without heart failure, with stage 5 chronic kidney disease, or end stage renal disease (cardiorenal, without heart failure, with stage 5 or end stage renal disease), I13.2 — Hypertensive heart and chronic kidney disease with heart failure and with stage 5 chronic kidney disease, or end stage renal disease (cardiorenal, with heart failure, with stage 5 or end stage renal disease), I15.0 — Renovascular hypertension (renovascular), I15.1 — Hypertension secondary to other renal disorders (due to, renal disorders NEC), I15.2 — Hypertension secondary to endocrine disorders (due to, pheochromocytoma), I15.8 — Other secondary hypertension (secondary NEC, specified NEC), I15.9 — Secondary hypertension, unspecified (secondary NEC), I16.0 — Hypertensive urgency (urgency), I16.1 — Hypertensive emergency (emergency), I16.9 — Hypertensive crisis, unspecified (crisis), I26.09 — Other pulmonary embolism with acute cor pulmonale (pulmonary, with, cor pulmonale, acute), I27.0 — Primary pulmonary hypertension (lesser circulation), I27.1 — Kyphoscoliotic heart disease (pulmonary, due to, kyphoscoliotic heart disease), I27.20 — Pulmonary hypertension, unspecified (pulmonary), I27.21 — Secondary pulmonary arterial hypertension (pulmonary, group 1), I27.22 — Pulmonary hypertension due to left heart disease (pulmonary, group 2), I27.23 — Pulmonary hypertension due to lung diseases and hypoxia (pulmonary, group 3), I27.24 — Chronic thromboembolic pulmonary hypertension (pulmonary, group 4), I27.29 — Other secondary pulmonary hypertension (pulmonary, group 5), I27.83 — Eisenmenger's syndrome (pulmonary, with, right to left shunt related to congenital heart disease), +54 more

Lab tests where this diagnosis supports Medicare coverage (NCD)

Medicare's National Coverage Determination (NCD) program lists this diagnosis as medical justification for these lab tests.

Lipid Panel, Thyroid Stimulating Hormone (TSH)

Contextual Map

Every relationship of I1A.0 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 I1A.0 with these 2 related codes in Claim Check

Hierarchy

• I00-I99 — Chapter 9: Diseases of the Circulatory System (I00-I99) (I00-I99)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Code First

• I10 — Essential (primary) hypertension[Code First]: “essential hypertension (I10)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• I15 — Secondary hypertension[Code First]: “secondary hypertension (I15.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026

Clinical classification (CCSR)

• CIR008 — Hypertension with complications and secondary hypertension[CCSR]— AHRQ CCSR for ICD-10-CM Diagnoses (HCUP)

MS-DRG Grouper

• DRG 304 — HYPERTENSION WITH MCC[MS-DRG]: “HYPERTENSION WITH MCC (MDC 05)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026
• DRG 305 — HYPERTENSION WITHOUT MCC[MS-DRG]: “HYPERTENSION WITHOUT MCC (MDC 05)”— CMS MS-DRG Definitions Manual (Appendix B) · FY2026

MDC crossing

• MDC 05 — Diseases and Disorders of the Circulatory System[MDC crossing]: “Diseases and Disorders of the Circulatory System — 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. 17,209 same-MDC procedures group here; browse them on the MDC page.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

• Hypertension, hypertensive (accelerated) (benign) (essential) (idiopathic) (malignant) (systemic), resistant (apparent treatment) (treatment) (true)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes

• I1A — Other hypertension[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Change history

• FY2024 — Added to the code set[Change history]— CMS release files (code change ledger) · icd10cm-fy2024

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

Nearest Codes in This Family

Official ICD-10-CM classifications closest to I1A.0 in its code family, with their registry titles.

• I1A — Other hypertension

View all codes in the I1A family