N18.4
BillableChronic kidney disease, stage 4 (severe)
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is N18.4 an HCC code?
Yes. N18.4 maps to Chronic Kidney Disease, Stage 4 (Severe) under the CMS-HCC V28 risk adjustment model (and Chronic Kidney Disease, Severe (Stage 4) under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for N18.4
For N18.4 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- 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
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed N18.4 during that encounter — not just copy-forwarded from a problem list.
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, Stage 4 (Severe) (HCC 327) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, N18.4 maps to Chronic Kidney Disease, Severe (Stage 4) (HCC 137) with a community, non-dual, aged base RAF weight of 0.289. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Verify GFR range of 15-29 mL/min/1.73m² is documented; patients at this stage typically require nephrology referral and dialysis planning. Because N18.4 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. 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, RAF weights, 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
- •Verify GFR range of 15-29 mL/min/1.73m² is documented; patients at this stage typically require nephrology referral and dialysis planning
- •Document comorbidities and complications such as anemia, bone disease, and hypertension that commonly accompany stage 4 CKD
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