N18.4 ICD-10-CM Code: Chronic kidney disease, stage 4 (severe)
N18.4 maps to CMS-HCC V28 327. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools
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FY 2026 Apr update / Diseases of the genitourinary system (N00-N99) / Acute kidney failure and chronic kidney disease (N17-N19)
N18.4
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceChronic kidney disease, stage 4 (severe)
Stage 4 chronic kidney disease where kidney function is severely decreased with a GFR of 15-29, indicating the kidneys are functioning at only 15-29% of normal capacity.
Buddy Insight
Stage 4 chronic kidney disease represents severe kidney dysfunction (GFR 15-29) requiring active preparation for renal replacement therapy and intensive management of complications.
CMS-HCC V28
MappedHCC 327
Code-level coefficient reference
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 188
Code-level coefficient reference
ESRD/PACE
MappedHCC 137
Code-level coefficient reference
RXHCC
MappedHCC 263
Code-level coefficient reference
Code Book Path
Inclusion Terms
OfficialNo inclusion terms are included in this display for N18.4. Check the code and parent instructions in the Code Book.
Excludes 2
Official- certain conditions originating in the perinatal period (P04-P96)Inherited from N00-N99, N17-N19
- certain infectious and parasitic diseases (A00-B99)Inherited from N00-N99, N17-N19
- complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from N00-N99, N17-N19
- congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)Inherited from N00-N99, N17-N19
- endocrine, nutritional and metabolic diseases (E00-E88)Inherited from N00-N99, N17-N19
- injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from N00-N99, N17-N19
- neoplasms (C00-D49)Inherited from N00-N99, N17-N19
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from N00-N99, N17-N19
- congenital renal failure (P96.0)Inherited from N00-N99, N17-N19
- drug- and heavy-metal-induced tubulo-interstitial and tubular conditions (N14.-)Inherited from N00-N99, N17-N19
- extrarenal uremia (R39.2)Inherited from N00-N99, N17-N19
- hemolytic-uremic syndrome (D59.3-)Inherited from N00-N99, N17-N19
- hepatorenal syndrome (K76.7)Inherited from N00-N99, N17-N19
- postpartum hepatorenal syndrome (O90.41)Inherited from N00-N99, N17-N19
- posttraumatic renal failure (T79.5)Inherited from N00-N99, N17-N19
- prerenal uremia (R39.2)Inherited from N00-N99, N17-N19
- renal failure complicating abortion or ectopic or molar pregnancy (O00-O07, O08.4)Inherited from N00-N99, N17-N19
- renal failure following labor and delivery (O90.41)Inherited from N00-N99, N17-N19
- renal failure postprocedural (N99.0)Inherited from N00-N99, N17-N19
Related Codes
Includes
OfficialNo Includes notes are included in this display for N18.4. Check the code and parent instructions in the Code Book.
Excludes 1
OfficialNo Excludes 1 notes are included in this display for N18.4. Check the code and parent instructions in the Code Book.
Code First
Official- any associated:Inherited from N18
- diabetic chronic kidney disease (E08.22, E09.22, E10.22, E11.22, E13.22)Inherited from N18
- hypertensive chronic kidney disease (I12.-, I13.-)Inherited from N18
Use Additional
Official- code, if applicable, to identify:Inherited from N18
- associated cachexia (E88.A)Inherited from N18
- kidney transplant status (Z94.0)Inherited from N18
Code Also
OfficialNo Code Also instructions are included in this display for N18.4. Check the code and parent instructions in the Code Book.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is N18.4 an HCC code?
Yes. N18.4 (Chronic kidney disease, stage 4 (severe)) maps to HCC 327, Chronic Kidney Disease, Severe (Stage 4) under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.514. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: N18.4 is billable and maps to V28 HCC 327, Chronic Kidney Disease, Severe (Stage 4). Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- N18.4
- Description
- Chronic kidney disease, stage 4 (severe)
- HCC (V28)
- HCC 327 — Chronic Kidney Disease, Severe (Stage 4)
- RAF reference coefficient
- 0.514
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work N18.4 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for N18.4
For N18.4, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Coder workflow notes
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What This Code Means
N18.4 is the ICD-10-CM diagnosis code for chronic kidney disease, stage 4 (severe). Stage 4 chronic kidney disease where kidney function is severely decreased with a GFR of 15-29, indicating the kidneys are functioning at only 15-29% of normal capacity. N18.4 sits in the ICD-10-CM chapter for diseases of the genitourinary system (n00-n99), within the section covering acute kidney failure and chronic kidney disease (n17-n19).
Under the CMS-HCC V28 risk adjustment model, N18.4 maps to Chronic Kidney Disease, Severe (Stage 4) (HCC 327) with a source-labeled community, non-dual, aged reference coefficient of 0.514. No V24 mapping is shown for N18.4; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Documentation must support CKD stage 4, eGFR 15-29 with a provider diagnosis. Re-documentation of the stage each year is required for risk adjustment purposes; stage 3 chart from a prior year does not carry forward to justify N18.4. For N18.4, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for N18.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Documentation must support CKD stage 4, eGFR 15-29 with a provider diagnosis. Re-documentation of the stage each year is required for risk adjustment purposes; stage 3 chart from a prior year does not carry forward to justify N18.4.
- •Do not assign N18.4 based on a single borderline eGFR value. CKD stage is a persistent diagnosis; the provider must state stage 4 in the assessment, not just order labs.
Clinical Significance
Stage 4 chronic kidney disease represents severe kidney dysfunction (GFR 15-29) requiring active preparation for renal replacement therapy and intensive management of complications. This diagnosis indicates advanced CKD with significant morbidity and healthcare resource utilization requiring specialized nephrology care.
Documentation Requirements
- ✓Chronic kidney disease stage 4 clearly documented
- ✓GFR values in the 15-29 range supporting stage 4 classification
- ✓Active nephrology management and renal replacement therapy planning
- ✓Assessment and management of CKD-related complications
- ✓Cardiovascular risk management and monitoring
- ✓Patient education regarding dialysis and transplant options
- ✓Laboratory monitoring for CKD-mineral bone disorder and anemia