The ICD-10-CM code range I10–I1A, titled Hypertensive Diseases, is one of the most frequently coded — and most frequently audited — diagnostic categories in all of medical billing. Despite the apparent simplicity of I10 (the workhorse code for essential hypertension), the full I10–I1A family contains critical distinctions that determine whether a claim is paid, questioned, or denied. This guide walks through every code in the range, the documentation standards that support each one, common coding traps, and a practical decision framework for selecting the right code every time.
What Does the ICD-10-CM Range I10–I1A Cover?
The I10–I1A range classifies all hypertensive diseases that are not associated with pregnancy, obstetrical care, or neonatal conditions. It captures essential (primary) hypertension in its uncomplicated form, hypertension with documented cardiac or renal involvement, secondary hypertension with an identified etiology, hypertensive crises, and — as of FY 2024 — resistant hypertension under the new I1A subcategory. Every code in this family belongs to Chapter 9 of ICD-10-CM, Diseases of the Circulatory System (I00–I99).
Key attributes of the I10–I1A range:
- Applies across all care settings: inpatient, outpatient, office, and ED
- Requires payer-compliant documentation of blood pressure readings and clinical management
- Several codes require additional codes to fully describe the clinical picture
- Excludes hypertension complicating pregnancy (coded to O10–O16)
- Excludes hypertension involving cerebral vessels (coded to I60–I69) and ocular vessels (H35.0–)
What Codes Are Included in the I10–I1A Family?
Understanding each code in the range prevents the single most common error in hypertension coding: defaulting to I10 regardless of the clinical picture. The table below maps every current category and its billable descendants.
| Code | Description | Billable? | Key Requirement |
|---|---|---|---|
| I10 | Essential (primary) hypertension | Yes | No documented heart or kidney disease |
| I11.0 | Hypertensive heart disease with heart failure | Yes | Requires additional I50.x code for heart failure type |
| I11.9 | Hypertensive heart disease without heart failure | Yes | Provider must document causal relationship |
| I12.0 | Hypertensive CKD with stage 5 CKD or ESRD | Yes | Requires N18.5 or N18.6 as additional code |
| I12.9 | Hypertensive CKD with stage 1–4 or unspecified CKD | Yes | Requires N18.1–N18.4 or N18.9 |
| I13.0 | Hypertensive heart and CKD with heart failure and stage 1–4 CKD | Yes | Requires both I50.x and N18.x |
| I13.10 | Hypertensive heart and CKD without heart failure, stage 1–4 CKD | Yes | Requires N18.x |
| I13.11 | Hypertensive heart and CKD without heart failure, stage 5 or ESRD | Yes | Requires N18.5 or N18.6 |
| I13.2 | Hypertensive heart and CKD with HF and stage 5 CKD or ESRD | Yes | Requires I50.x and N18.5/N18.6 |
| I15.0 | Renovascular hypertension | Yes | Requires secondary etiology documentation |
| I15.1 | Hypertension secondary to other renal disorders | Yes | Underlying renal condition coded first |
| I15.2 | Hypertension secondary to endocrine disorders | Yes | Underlying endocrine condition coded first |
| I15.8 | Other secondary hypertension | Yes | Specific etiology must be documented |
| I15.9 | Secondary hypertension, unspecified | Yes | Use only when etiology is genuinely unknown |
| I16.0 | Hypertensive urgency | Yes | Severe BP elevation, no acute organ damage |
| I16.1 | Hypertensive emergency | Yes | Severe BP elevation WITH acute organ damage |
| I16.9 | Hypertensive crisis, unspecified | Yes | Avoid when urgency vs. emergency is determinable |
| I1A.0 | Resistant hypertension | Yes | Code first the specific type (I10 or I15.x) |
What Does This Range Specifically Exclude?
- Hypertensive disease complicating pregnancy, childbirth, or the puerperium → use O10–O16
- Primary (essential) hypertension involving cerebral vessels → use I60–I69
- Primary hypertension involving vessels of the eye → use H35.0–
- Neonatal hypertension → use P29.2
- Pulmonary hypertension → use I27.0, I27.2x
When Should You Use I10 vs. I11, I12, or I13?
This is the most consequential decision point in hypertension coding. Using I10 when the patient has documented hypertensive heart disease or CKD is a top audit finding and may result in downcoded DRGs in inpatient settings.
Follow this decision sequence:
- Does the patient have a documented hypertension diagnosis? If not, use R03.0 (elevated blood pressure reading without diagnosis) and stop.
- Is hypertension documented as a reason for encounter or active management today? If only historical and not managed, consider Z87.39 (personal history of cardiovascular disease) rather than an active code.
- Does the patient also have documented heart disease (e.g., heart failure, LV hypertrophy)? If yes, and the provider documents or implies a causal relationship, use I11.x rather than I10.
- Does the patient also have chronic kidney disease (CKD)? Per ICD-10-CM Official Coding Guidelines Section I.C.9, ICD-10-CM presumes a causal relationship between hypertension and CKD — no explicit provider statement is required. Assign I12.x automatically.
- Does the patient have BOTH heart disease and CKD? Assign I13.x, which is the combination code for all three conditions.
- Is the hypertension secondary to a known underlying cause? Assign the underlying condition first, then I15.x.
- Is there documented resistant hypertension? Assign the primary hypertension type first (I10 or I15.x), then add I1A.0.
How Does I10 Differ From I11.9?
Coders most often confuse I10 and I11.9 because both involve hypertension without active heart failure. The distinction is whether hypertensive heart disease — typically evidenced by left ventricular hypertrophy, cardiomegaly, or diastolic dysfunction — has been documented.
| Feature | I10 | I11.9 |
|---|---|---|
| Heart disease present? | No | Yes (LVH, diastolic dysfunction, etc.) |
| Causal relationship required | N/A | Provider must state or imply HTN caused the cardiac condition |
| Additional code required? | No | No (but I50.x needed if heart failure present) |
| Audit sensitivity | Moderate | High — requires supporting documentation |
| Common setting | Outpatient primary care | Cardiology, inpatient |
In practice, coders frequently encounter I11.9 being under-reported because providers document hypertension and left ventricular hypertrophy as separate problems without explicitly linking them. This is a legitimate query opportunity: ask the provider whether the LVH is attributable to the patient’s longstanding hypertension.
What Documentation Is Required to Support I10–I1A Codes?
What Must the Provider Document in the Clinical Notes?
For any code in the I10–I1A range, the clinical note must demonstrate that hypertension is an active diagnosis being managed at this encounter — not simply a problem list entry that goes unaddressed. Auditors commonly flag encounters where the only documentation is “HTN — stable” without any supporting clinical activity.
Required documentation elements for a compliant hypertension encounter:
- A confirmed diagnosis of hypertension (not just an elevated reading)
- Current blood pressure reading(s) recorded in the note
- Evidence of clinical management: medication review, adjustment, patient counseling, or referral
- For I11.x: provider statement or implication linking hypertension to the cardiac condition
- For I12.x: both hypertension and CKD must be documented (causal link is presumed by guideline)
- For I13.x: all three conditions (HTN, heart disease, CKD) actively documented in the note
- For I16.x: BP reading at or above 180/120 mmHg and clinical characterization of urgency vs. emergency
- For I1A.0: documentation that the patient fails to reach goal BP despite adherence to three or more antihypertensive medications at optimal doses, including a diuretic
Which Diagnostic or Lab Results Support These Codes?
- Ambulatory blood pressure monitoring (ABPM) readings confirming sustained elevation
- Basic metabolic panel (BMP) or CMP showing creatinine and GFR for CKD staging (required for I12.x and I13.x)
- Echocardiogram demonstrating LVH or reduced ejection fraction (supports I11.x)
- Urinalysis with protein (supporting hypertensive nephropathy)
- Medication reconciliation documentation listing three or more antihypertensives at optimized doses (required for I1A.0)
- Secondary workup results: aldosterone-renin ratio, thyroid panel, renal artery imaging (supports I15.x)
What Is the Documentation Standard for Inpatient vs. Outpatient Settings?
| Element | Outpatient | Inpatient |
|---|---|---|
| Diagnosis basis | Provider’s documented diagnosis | Attending’s final diagnosis in discharge summary |
| Causal relationship (HTN+heart) | Requires provider statement | Requires provider statement |
| Causal relationship (HTN+CKD) | Presumed by guideline | Presumed by guideline |
| Uncertain diagnoses (“probable”) | Cannot code uncertain diagnoses | Can code to the highest degree of certainty |
| CKD staging | Required for I12/I13 additional codes | Required — CDI may query if absent |
| Principal diagnosis sequencing | Reason for encounter determines order | Condition responsible for admission determines order |
How Do I10–I1A Codes Affect Medical Billing and Claims?
Hypertension codes are among the most scrutinized in revenue cycle compliance. Payers — particularly Medicare Advantage plans and commercial insurers — use hypertension coding as a risk adjustment trigger, which means accurate capture of comorbid conditions (I11.x, I12.x, I13.x) directly affects the plan’s risk score and the provider’s reimbursement under value-based contracts.
Key billing considerations:
- I10 alone carries a lower risk-adjustment weight than combination codes — under-coding hypertensive heart or kidney disease costs capitated practices significant revenue
- CKD staging codes (N18.x) are mandatory with I12.x and I13.x; claims submitted without them may be rejected or generate a request for records
- I16.x codes (hypertensive crisis) are flagged as “Questionable as Admission Diagnosis” — they should rarely appear as the sole principal diagnosis on an inpatient claim
- For I1A.0 (resistant hypertension), the sequencing requirement (I10 or I15.x first) must be followed exactly, or the claim may fail NCCI edit review
What CPT or Procedure Codes Are Commonly Billed With I10–I1A?
| CPT Code | Description | Common Pairing Context |
|---|---|---|
| 99213–99215 | Office/outpatient E&M | Routine HTN management with I10 |
| 93000 | Electrocardiogram | Cardiac evaluation supporting I11.x |
| 93306 | Echocardiography | LVH or EF documentation for I11.x |
| 80048 | Basic metabolic panel | CKD staging confirmation for I12/I13 |
| 82565 | Creatinine | CKD monitoring |
| 36415 | Venipuncture | Lab draws for secondary workup (I15.x) |
| 99291–99292 | Critical care E&M | Hypertensive emergency (I16.1) |
Are There Prior Authorization or Coverage Restrictions?
- Most commercial payers do not require prior auth for routine hypertension E&M visits, but specialist referrals for secondary hypertension workup (endocrinology, nephrology) often do
- Medicare covers hypertension screening under the Annual Wellness Visit (AWV) — but active management is billed separately under the appropriate E&M level
- Some Medicare Advantage plans require HEDIS-compliant blood pressure documentation to validate quality measure credit
- Resistant hypertension (I1A.0) may trigger payer requests for clinical records to confirm the three-drug trial before approving newer agents such as finerenone or renal denervation procedures
What Coding Errors Should You Avoid With I10–I1A?
The following errors represent the highest-frequency findings in hypertension coding audits, ranked by audit risk:
- Defaulting to I10 when comorbid heart or kidney disease is documented. This is the single most common error and the one with the greatest revenue impact in risk-adjusted payment models.
- Assigning I12.x or I13.x without the required N18.x additional code. CKD stage is mandatory — unspecified CKD (N18.9) is acceptable only when staging is genuinely absent from documentation.
- Using I16.x without also coding the underlying hypertension. The “Code also” instruction for category I16 is mandatory, not optional.
- Sequencing I1A.0 first. This code carries a “Code first” instruction — I10 or I15.x must appear before I1A.0.
- Coding I10 for an elevated blood pressure reading without a formal diagnosis. R03.0 is the correct code when the provider has not established hypertension as a diagnosis.
- Using I15.9 (secondary hypertension, unspecified) when the etiology is actually documented. If the chart identifies renovascular disease, endocrine disorder, or another specific cause, the more specific I15.0–I15.8 code applies.
- Omitting hypertension from claims where it is actively managed. Failure to capture all conditions addressed at an encounter constitutes under-coding and affects risk adjustment and quality metrics.
What Do Auditors Look for When Reviewing Claims With I10–I1A?
- Blood pressure reading present in the note and consistent with the coded diagnosis
- Evidence of active management (medication changes, referral, counseling) — not just passive documentation
- For I16.x: clinical differentiation between urgency and emergency (presence or absence of acute end-organ damage)
- For I11.x: provider language connecting hypertension to cardiac findings
- For I12.x/I13.x: CKD stage supported by lab values in the note
- For I1A.0: medication list showing three or more appropriately dosed antihypertensives
How Does the I10–I1A Family Relate to Other ICD-10 Codes?
The hypertensive disease range has multiple cross-code relationships that affect sequencing and simultaneous use:
| Related Code | Relationship Type | Key Distinction |
|---|---|---|
| R03.0 | Excludes1 from I10 | Elevated BP without a hypertension diagnosis — never code with I10 |
| O10–O16 | Excludes1 from I10–I1A | Hypertension complicating pregnancy — use obstetric codes |
| I60–I69 | Excludes2 from I10 | HTN involving cerebral vessels — can code alongside I10 |
| H35.0– | Excludes2 from I10 | HTN involving ocular vessels — can code alongside I10 |
| N18.1–N18.6, N18.9 | Required additional code | CKD staging — mandatory with I12.x and I13.x |
| I50.x | Required additional code | Heart failure type — mandatory when I11.0 or I13.x involves HF |
| I27.0, I27.2x | Separate category | Pulmonary hypertension — not part of I10–I1A at all |
| E11.x | Use additional | Type 2 diabetes frequently coexists; code separately |
| Z87.39 | Historical use | Personal history of cardiovascular disease — for resolved conditions |
What Is the Correct Code Sequencing When I10–I1A Appears With Other Diagnoses?
- For I11.x, I12.x, I13.x: the combination hypertension code sequences first (it is the etiology), followed by any required additional codes (N18.x, I50.x).
- For I15.x: the underlying condition (e.g., renal artery stenosis, primary aldosteronism) sequences first as the etiology, followed by the secondary hypertension code.
- For I16.x: sequencing is discretionary based on the reason for the encounter; however, the underlying hypertensive disease code (I10–I15, I1A) must also appear.
- For I1A.0: the specific type of hypertension (I10 or I15.x) must be sequenced before I1A.0 — this is a mandatory “Code first” instruction, not optional.
- In inpatient settings, if both hypertensive crisis and the underlying hypertension are present, the condition primarily responsible for the admission determines the principal diagnosis.
Real-World Coding Scenario — How I10–I1A Codes Are Applied in Practice
Scenario: A 67-year-old male presents to his cardiologist for a follow-up visit. His medical history includes hypertension (diagnosed 12 years ago), stage 3b CKD (documented by nephrology with GFR of 38), and recently diagnosed diastolic heart failure. The provider reviews his medications — lisinopril, amlodipine, and chlorthalidone — and notes the patient’s BP is 148/86. The note states: “Patient with hypertensive heart and kidney disease. Heart failure with preserved ejection fraction confirmed on echo last month. CKD stage 3b stable.” The provider adjusts the lisinopril dose.
Correct Code Application
- I13.0 — Hypertensive heart and chronic kidney disease with heart failure and stage 1–4 CKD (combination code capturing all three conditions)
- I50.32 — Chronic diastolic (congestive) heart failure (required additional code specifying type of HF)
- N18.33 — CKD, stage 3b (required additional code specifying CKD stage)
Common Mistake in This Scenario
Incorrectly assigned codes and why they fail:
- I10 + I50.32 + N18.33: Fails because it ignores the hypertensive etiology of both the heart and kidney disease — I10 is for uncomplicated primary hypertension only
- I11.0 + N18.33: Fails because it omits the hypertensive kidney disease when both cardiac and renal involvement are documented — I13.x must be used when all three conditions coexist
- I13.0 without N18.33: Fails claims editing — CKD stage is a mandatory additional code; the claim will be returned or denied
Frequently Asked Questions About ICD-10 Codes I10–I1A
Is ICD-10 Code I10 Still Valid for Fiscal Year 2026?
ICD-10 code I10 remains a valid, billable diagnosis code for FY 2026 (October 1, 2025 through September 30, 2026) with no changes to its description or validity status. Coders should verify the ICD-10-CM Official Coding Guidelines published annually by CMS for any updates to instructional notes or guideline interpretations.
What Is the Difference Between I16.0 (Hypertensive Urgency) and I16.1 (Hypertensive Emergency)?
I16.0, hypertensive urgency, applies when blood pressure is severely elevated — typically at or above 180/120 mmHg — but there is no evidence of acute end-organ damage. I16.1, hypertensive emergency, applies when the same level of BP elevation is accompanied by acute damage to the heart, kidneys, brain, or eyes, such as acute myocardial infarction, AKI, or hypertensive encephalopathy. The provider must explicitly document the presence or absence of organ damage for the distinction to be coded accurately.
When Should I Use I1A.0 Instead of Just I10?
I1A.0 (resistant hypertension) should be assigned only when the provider documents that the patient’s blood pressure remains uncontrolled despite adherence to three or more antihypertensive agents at optimal doses — one of which should ideally be a diuretic. I10 (or I15.x) must be sequenced before I1A.0 per the “Code first” instruction. In practice, coders often miss this code entirely because providers may use phrases like “uncontrolled hypertension” rather than “resistant hypertension” — a query to the provider may be warranted to clarify clinical intent.
Does CKD Always Require a Separate Code When I12.x or I13.x Is Used?
Yes, CKD stage must always be captured with an additional code from category N18 when coding I12.x or I13.x. This is a mandatory coding convention, not optional. Submitting I12.9 or I13.10 without N18.x will often trigger a claim edit or records request, and it also affects CMS risk-adjustment calculations that directly impact value-based contract performance.
Can I Code I10 and I11.x Together on the Same Claim?
No. I10 and I11.x are mutually exclusive — I11.x is the combination code that replaces I10 when hypertensive heart disease is documented. Using both codes on the same claim would represent a coding audit red flag and may be flagged by NCCI edits or payer logic. The same principle applies to I12.x and I13.x — never combine them with I10 when the combination code fully captures the clinical picture.
Is Secondary Hypertension Coded Differently Than Essential Hypertension?
Secondary hypertension (I15.x) requires a fundamentally different sequencing approach. Unlike essential hypertension (I10), where hypertension itself is the principal condition, secondary hypertension requires the underlying etiology to be coded first — for example, primary hyperaldosteronism (E26.09) before I15.2, or renal artery stenosis (I77.3) before I15.0. Failure to sequence the etiology first is a common coding error that distorts the clinical picture and may misrepresent medical necessity.
Does Medicare Cover Hypertension Management Under the Annual Wellness Visit?
Medicare’s Annual Wellness Visit (AWV) includes blood pressure screening as a covered preventive service, but active management of diagnosed hypertension — medication adjustment, counseling, or diagnostic review — must be billed separately using the appropriate E&M level (99213–99215) with I10 or the applicable hypertensive disease code. Billing both the AWV and a problem-focused E&M visit on the same date is allowed when a separately identifiable service is documented, but requires a -25 modifier on the E&M claim.
Key Takeaways
Every coder working with the I10–I1A range should internalize these core principles:
- I10 is for uncomplicated primary hypertension only — as soon as documented heart or kidney disease enters the picture, a combination code (I11.x, I12.x, I13.x) is required
- CKD and hypertension always presume a causal relationship under ICD-10-CM guidelines — no provider query is needed to link them
- I1A.0 requires a “Code first” sequence — I10 or I15.x must appear before it on the claim
- I16.x (hypertensive crisis) always requires an additional hypertensive disease code — it is never reported in isolation
- The distinction between I16.0 and I16.1 hinges entirely on documented end-organ damage — this must come from the provider’s note, not coder inference
- Under-coding hypertension comorbidities in risk-adjusted payment models has direct financial consequences for both providers and payers
- For the most current guidance on ICD-10-CM Official Coding Guidelines, always reference the CMS ICD-10 resources page and the AHA Coding Clinic for official guidance on sequencing disputes
For authoritative official guidance, refer to CMS ICD-10-CM Official Coding Guidelines (Section I.C.9), published annually at cms.gov, and the AHA Coding Clinic for ICD-10-CM/PCS, which has addressed hypertensive combination coding in multiple advisory opinions.