Common Nephrology ICD-10 Codes (2026)

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1. Introduction — The Real Cost of Getting It Wrong

Most nephrology practices don't lose money because of bad medicine. They lose it because of a single missing code, a mismatched diagnosis pointer, or a provider note that says 'kidney disease' without specifying the stage. In nephrology, those documentation gaps translate directly into denied claims, reduced HCC scores, compliance flags, and in the case of ESRD Monthly Capitation Payments entire months of revenue left on the table.

ICD-10-CM coding in nephrology isn't complicated, but it is unforgiving. The N18 code family for Chronic Kidney Disease, the N18.6/Z99.2 pairing for ESRD, and the intricate web of combination codes for hypertensive and diabetic kidney disease all follow strict sequencing rules that automated payer systems know better than many billing teams do.

This guide was built for the people who need it most: the nephrologist trying to document faster without coding errors, the biller who keeps seeing ESRD claims bounce, and the practice manager asking why the dialysis revenue line looks so unpredictable. Everything here reflects the FY 2026 ICD-10-CM code set, effective October 1, 2025.

2. What's New in FY 2026 — ICD-10-CM Nephrology Updates

🆕  FY 2026 went live October 1, 2025 — featuring 487 new codes, 28 deletions, and 38 revisions. Here's what nephrology professionals need to know:

The most impactful nephrology-specific additions in FY 2026 fall in Chapter 14 (Genitourinary System Diseases, N00–N99) and Chapter 4 (Endocrine & Metabolic Diseases, E00–E89). Here are the key changes:

●      New codes for Immune Complex Membranoproliferative Glomerulonephritis (IC-MPGN) — distinguishing idiopathic vs. secondary IC-MPGN. Previously coded under N00.5 or N04.5, these now have dedicated codes that demand specific physician documentation of the IC-MPGN subtype.

●      New codes for APOL1-mediated kidney disease, reflecting hereditary nephropathy driven by APOL1 gene variants. Coders should begin querying providers when African American patients with focal segmental glomerulosclerosis or non-diabetic ESRD are encountered.

●      E11.A — Type 2 Diabetes Mellitus in Remission — is a brand-new FY 2026 code. When DM is in remission but CKD persists, coders should use E11.A plus the appropriate N18.x stage code. Do NOT revert to E11 (active DM) out of habit.

●      New flank pain/tenderness codes (R10.8A-, R10.A-) add anatomic specificity useful in nephrology workups. These can support medical necessity for imaging studies.

●      CMS-HCC v28 model remains active for 2026, with ESRD-related HCCs 136 and 137 carrying significant risk adjustment weight. Unspecified N18.9 continues to carry minimal HCC value a costly oversight.

⚠  CRITICAL: The N18 code family (N18.1–N18.6) has NO new additions or deletions in FY 2026. The subcodes N18.31 and N18.32 (Stage 3a/3b distinction) remain active from the prior update. All N18 codes should be verified against your EHR pick-lists annually.

3. CKD Staging — Complete 2026 ICD-10-CM Code Table

The N18 category is the foundation of nephrology coding. Every code selection hinges on the documented GFR-based stage, which must come directly from the treating provider — not from a lab value interpreted by the coder. KDIGO guidelines define the staging thresholds that CMS follows.

The table below maps every CKD stage to its ICD-10 code, GFR range, clinical context, and risk adjustment significance:

📌  CODING RULE: A provider cannot be assumed to have intended a specific stage. If the note says 'worsening CKD' without staging, the coder must query before assigning. Using N18.9 instead of querying is the most expensive shortcut in nephrology billing.

4. ESRD & Dialysis Coding Deep Dive

N18.6 is the most financially sensitive code in nephrology practice. It is the required diagnosis for every Monthly Capitation Payment (MCP) claim, every vascular access procedure, and every hemodialysis or peritoneal dialysis session billed to Medicare. Getting it wrong — or leaving it incomplete — triggers automatic payer edits that bypass human review entirely.

The ESRD Code Pair You Must Never Split: N18.6  (End-Stage Renal Disease)  +  Z99.2  (Dependence on Renal Dialysis) Neither code alone satisfies payer medical necessity review for ESRD services. Build both into every ESRD billing template as a locked pair.

ESRD MCP billing structure (CPT codes 90960–90966) determines your monthly payment tier based on the number of face-to-face physician visits. The documentation requirement is specific: each visit needs a progress note covering dialysis adequacy review, medication management, vascular access site evaluation, and treatment plan. Miss a visit from the note set, and payer analytics will downcode 90960 to 90961 automatically — a revenue cut that compounds across an entire ESRD panel.

4a. AKI vs. ESRD — The Distinction That Changes Everything

Acute Kidney Injury (N17.x) and ESRD (N18.6) are not interchangeable, and billing teams that blur this distinction face both clinical accuracy problems and compliance risk. AKI is coded with N17.0 (with tubular necrosis), N17.1 (with acute cortical necrosis), N17.2 (with medullary necrosis), or N17.9 (unspecified) when the acute episode is the primary driver. When AKI occurs on top of existing CKD, both codes are reported — with sequencing determined by what drove the encounter.

5. Hypertensive CKD — Combination Coding Rules

One of the most common coding errors in nephrology is using I10 (essential hypertension) alongside N18.x as if they're unrelated. ICD-10-CM's Official Coding Guidelines are clear: when hypertension and CKD coexist, a causal relationship is presumed, and combination codes from the I12 or I13 series are required. Coding them separately is a technical error that payer scrubbers catch before the claim ever reaches an adjudicator.

💡  EXPERT TIP: I12.9 alone is incomplete. You must always pair it with the appropriate N18.x stage code. A claim showing I12.9 without N18.2 or another stage-specific code will be flagged for missing specificity.

6. Diabetic CKD — Correct Code Sequences for DM1 & DM2

Diabetic nephropathy is the leading cause of ESRD in the United States. Despite this, it remains one of the most commonly under-specified diagnoses in nephrology coding. The ICD-10-CM framework requires the diabetes code to be listed first, with the N18.x stage code added as a secondary. Missing the stage, or using unspecified E11.9 when a more specific diabetes code applies, degrades both the HCC capture and the clinical accuracy of the record.

7. HCC Risk Adjustment — Why Stage Specificity Is Worth Real Money

Under CMS-HCC v28 (active in 2026), kidney disease maps to HCC categories 136 and 137, with ESRD and stage 4–5 CKD generating the highest risk-adjustment factor (RAF) scores. The financial stakes are direct: a Medicare Advantage patient coded as N18.9 (unspecified) generates a significantly lower RAF score than the same patient correctly coded as N18.6 with I12.0 and Z99.2.

For Medicare Advantage plans and ACO practices, a 1–3% loss in HCC capture across a large patient panel can translate to millions of dollars in lost revenue annually — with additional exposure to Risk Adjustment Data Validation (RADV) audits when codes don't align with documented clinical severity.

8. Common Denial Patterns & Prevention Strategies

The 2026 nephrology billing environment has introduced a new category of denials: correct claims rejected by AI-driven payer editing systems that flag statistical anomalies rather than actual coding errors. But the foundational denial triggers remain the same, and they are preventable. Here are the six most expensive patterns:

9. Documentation Requirements — What Auditors Look For

Documentation is the only thing that separates a paid claim from a denied one — and a defensible record from an audit liability. The checklist below is built from CMS audit expectations, MAC guidance, and the documentation elements most frequently flagged in nephrology billing reviews:

Documentation Element	Required For	Auditor Priority
CKD stage explicitly stated by provider	All N18.x codes	🔴 Critical
GFR value or range in the note	N18.1–N18.6 selection	🔴 Critical
Cause of CKD documented (DM, HTN, GN, etc.)	Combination code selection	🔴 Critical
Dialysis status (HD, PD, home dialysis)	N18.6 + Z99.2	🔴 Critical
Dialysis session dates (monthly)	MCP code tier 90960–90962	🔴 Critical
Face-to-face visit count for month	CPT 90960 vs. 90961 vs. 90962	🔴 Critical
Transplant status documented	Z94.0	🟡 High
Blood pressure documentation when HTN present	I12.x / I13.x selection	🟡 High
AKI vs. CKD distinction clearly noted	N17 vs. N18 coding	🟡 High
Complications noted (anemia, mineral bone disease)	D63.1, N25.81 add-ons	🟢 Moderate
Vascular access type and site	Access procedure CPTs	🟢 Moderate
Medication list (ESAs, phosphate binders)	Medical necessity support	🟢 Moderate

10. Monthly ESRD Billing Checklist — Step-by-Step Workflow

Use this checklist at the end of every billing month for each active ESRD patient in your panel.

✔  Confirm dialysis status and modality (HD, PD, home HD) for the month

✔  Verify N18.6 is the primary diagnosis — check that N18.5 or N18.9 has not been defaulted from the EHR

✔  Confirm Z99.2 is present on every ESRD claim

✔  Count documented face-to-face visits and select correct MCP code (90960 / 90961 / 90962)

✔  Review all progress notes for completeness: dialysis adequacy, medications, access site, treatment plan

✔  Identify separately billable services (unrelated E&M, vascular access procedures, inpatient consults)

✔  Verify combination codes for HTN-CKD (I12.x) and DM-CKD (E11.65 + N18.6)

✔  Check that all dialysis CPT codes are linked to N18.6 via the diagnosis pointer

✔  Submit before month-end; log submission dates for timely filing tracking

✔  Review ERA/remittance for MCP downcodes — investigate any 90960→90961 patterns

11. Case Studies — How Coding Choices Play Out in Practice

Case Study A: The Stage 3b Patient with Diabetes and Hypertension

Clinical Scenario: A 68-year-old patient with Type 2 diabetes (on metformin + insulin), hypertension (BP 142/88), and documented CKD Stage 3b (eGFR 38). No dialysis. Presents for quarterly nephrology visit.

Correct code sequence: E11.65 (Type 2 DM with hyperglycemia) → N18.32 (CKD Stage 3b) → I12.9 (HTN + CKD Stage 1–4). The HTN-CKD relationship uses I12.9, NOT a separate I10. The DM is sequenced first as the primary underlying etiology of the CKD per ICD-10-CM convention. E11.65 captures better clinical specificity than E11.9.

Case Study B: ESRD Patient Switching from Hemodialysis to Peritoneal Dialysis

Clinical Scenario: Patient transitions from in-center HD to home PD in month 3. Physician provides 2 face-to-face visits during the MCP month.

Code set: N18.6 + Z99.2. CPT: 90945 or 90947 per dialysis session, or home dialysis MCP code 90966 if managing home PD monthly. Billing mistake to avoid: continuing to use in-center hemodialysis codes after PD transition. Modality change must trigger a CPT update, confirmed against the dialysis center records.

Case Study C: AKI-on-CKD Hospitalization

Clinical Scenario: CKD Stage 4 patient admitted for AKI triggered by contrast nephropathy. Discharge summary documents AKI as primary diagnosis, with CKD Stage 4 as comorbidity.

Inpatient principal diagnosis: N17.9 (AKI unspecified) or more specific N17.x per documentation. Secondary: N18.4 (CKD Stage 4). Do not upgrade to N18.5 or N18.6 unless the physician explicitly states the patient has progressed or initiated dialysis. AKI is treatable and potentially reversible — sequencing reflects what drove the admission.

12. Complete 2026 Nephrology ICD-10 Quick Reference Cheat Sheet

Print this. Post it. Share it with your billing team.

Code	Short Description	Billable?	Pair With
N18.1	CKD Stage 1	Yes	N18.1 standalone or with I12.9/E11.9
N18.2	CKD Stage 2	Yes	Same as above
N18.31	CKD Stage 3a	Yes	Same as above
N18.32	CKD Stage 3b	Yes	Same as above
N18.4	CKD Stage 4	Yes	I12.9 or E11.65 + dialysis planning codes
N18.5	CKD Stage 5 (no dialysis)	Yes	NOT for active dialysis patients
N18.6	ESRD	Yes	Always + Z99.2 for dialysis; + Z94.0 for transplant
N18.9	CKD Unspecified	Avoid	Only if stage truly undocumentable
Z99.2	Dialysis Dependence	Yes (add-on)	Always with N18.6
Z94.0	Kidney Transplant Status	Yes (add-on)	With N18.x if residual CKD
I12.0	HTN + CKD Stg 5/ESRD	Yes	+ N18.5 or N18.6
I12.9	HTN + CKD Stg 1–4	Yes	+ N18.1–N18.4
I13.0	HTN + HF + CKD Stg 1–4	Yes	+ N18.x + I50.x
I13.2	HTN + HF + ESRD	Yes	+ N18.6 + I50.x
E11.65	Type 2 DM + hyperglycemia	Yes	+ N18.x for CKD stage
E11.A	Type 2 DM in Remission	Yes	NEW FY2026
N17.9	AKI, unspecified	Yes	Can code with N18.x if AKI-on-CKD
E11.22	Type 2 DM w/ diabetic CKD (legacy)	Yes	+ N18.x

13. Frequently Asked Questions (2026)

Q1: What is the ICD-10 code for CKD Stage 3?

A: CKD Stage 3 is split into two specific subcodes: N18.31 for Stage 3a (eGFR 45–59) and N18.32 for Stage 3b (eGFR 30–44). Using N18.3 as a standalone code is no longer valid — both subcodes are required to be selected based on documented GFR values.

Q2: What is the ICD-10 code for ESRD?

A: N18.6 is the code for End-Stage Renal Disease. It must always be paired with Z99.2 (Dependence on Renal Dialysis) for dialysis patients. Neither code is complete without the other for ESRD billing purposes.

Q3: Can a coder assign a CKD stage from a lab result?

A: No. Coders cannot assign a CKD stage based on a GFR value in the lab report alone. The provider must document the stage explicitly in the note. If the stage is not documented, the coder must query the provider before code assignment.

Q4: Should I code hypertension separately from CKD?

A: No. ICD-10-CM assumes a causal relationship between hypertension and CKD when both are present. Use I12.x (or I13.x if heart failure is also present) rather than coding I10 and N18.x separately. Separate coding is a technical error.

Q5: What changed for nephrology in the FY 2026 ICD-10-CM update?

A: Key FY 2026 changes include: new IC-MPGN codes distinguishing idiopathic vs. secondary forms, new APOL1-mediated kidney disease codes, and the E11.A code for Type 2 DM in remission (which still requires N18.x if CKD persists).

Q6: Is N18.9 ever acceptable to use?

A: N18.9 (CKD unspecified) should be reserved only for situations where the stage is genuinely not documented and cannot be queried in time. Repeated use of N18.9 is an audit red flag and results in near-zero HCC contribution for risk-adjusted patients.

Q7: What CPT codes are used for ESRD monthly billing?

A: The primary MCP codes for adult ESRD patients are 90960 (4+ face-to-face visits), 90961 (2–3 visits), and 90962 (1 visit). Home dialysis is managed under 90966. Session-based dialysis uses 90935/90937 (hemodialysis) and 90945/90947 (peritoneal dialysis). MCP and session codes cannot be billed in the same month for the same patient.

Q8: What codes are used for diabetic kidney disease?

A: Type 2 DM with CKD is typically coded E11.65 (or E11.9 for uncontrolled) plus the appropriate N18.x stage. The new E11.A code applies when DM is in remission but CKD persists. Type 1 DM uses the E10 series. Diabetes code is always sequenced first.

Q9: Does a kidney transplant eliminate CKD coding?

A: No. Transplant patients with residual CKD should be coded with the appropriate N18.x stage plus Z94.0 (Kidney Transplant Status). Z94.0 indicates transplant history without implying a complication. If a transplant complication is present, use T86.1x codes.

Q10: What is the difference between N17 and N18?

A: N17 codes are for Acute Kidney Injury (AKI) — a sudden, potentially reversible decline in renal function. N18 codes are for Chronic Kidney Disease — an irreversible, progressive loss of kidney function. Both can be coded simultaneously when AKI occurs on top of existing CKD.

Q11: How does CKD coding affect Medicare Advantage payments?

A: CKD codes map to HCC categories 136 and 137 under CMS-HCC v28. ESRD (N18.6) generates the highest RAF score in the renal category. Unspecified N18.9 generates minimal HCC value, costing MA plans significant per-member revenue annually.

Q12: What are the most common ESRD claim denial reasons?

A: The six most common ESRD denial triggers are: N18.5 used for active dialysis patient (should be N18.6), Z99.2 absent from claim, hypertension coded separately instead of using I12.x, N18.9 used instead of a staged code, dialysis CPT not linked to N18.6, and MCP code tier mismatch due to undocumented visits.

Q13: What documentation is required for the Monthly Capitation Payment?

A: Each MCP month requires: confirmed dialysis modality, documented face-to-face visit count with dated progress notes, each note covering dialysis adequacy review, medication management, vascular access evaluation, and treatment plan. Missing one documented element can trigger a downcode from 90960 to 90961 or 90962.

Q14: Can AI coding tools be used for nephrology?

A: AI-assisted coding is growing in nephrology RCM, but must be validated by certified coders. AI tools can flag unspecified codes, suggest combination code opportunities, and identify missing Z codes — but they cannot replace clinical judgment or provider queries. CMS RADV audits require MEAT (Monitor, Evaluate, Assess, Treat) evidence that AI tools alone cannot guarantee.

Q15: Where should I go if my nephrology practice has high denial rates?

A: Start with a denial root-cause analysis broken down by code, provider, and payer. Identify whether the issue is documentation, combination coding, modifier application, or payer-specific edit logic. Many practices benefit from a nephrology-specific billing audit before implementing process changes. Sirius Solutions Global offers specialized nephrology billing reviews designed to identify systemic denial patterns, not just individual claim errors.

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⚠  DISCLAIMER

This article is provided for informational and educational purposes only. It does not constitute legal, compliance, or professional medical coding advice. ICD-10-CM codes, CMS guidelines, and payer-specific policies are updated regularly; readers should always verify code accuracy against the current FY ICD-10-CM code set, Official Coding Guidelines published by NCHS and CMS, and applicable Local Coverage Determinations (LCDs) and National Coverage Determinations (NCDs) from their Medicare Administrative Contractor (MAC). Sirius Solutions Global makes no warranty, express or implied, regarding the accuracy, completeness, or suitability of this content for any particular purpose. Clinical and coding decisions should always involve qualified certified medical coders (CPC, CCS, or equivalent credentialed by AAPC or AHIMA) and, where appropriate, consultation with legal counsel or compliance professionals. This content does not establish a client relationship between the reader and Sirius Solutions Global. © 2026 Sirius Solutions Global. All rights reserved.