Crystal's Coder Hub🧬 ICD-10 CM N18.30 — Chronic Kidney Disease, Stage 3 Unspecified
Billable Code Confirmed
ICD-10-CM N18.30 is a valid, billable 6-character ICD-10-CM diagnosis code for FY2026. Characters 1-3 (N18) define the category (Chronic kidney disease); character 4 (.3) defines stage 3 (moderate); character 5 (0) specifies that the substage is unspecified — distinguishing this code from N18.31 (stage 3a) and N18.32 (stage 3b). All six characters are required for submission; no additional characters are needed or available.
Non-Billable Parent Codes — Never Submit These
- ❌
N18— 3-character header — no stage, type, or substage specificity present- ❌
N18.3— 5-character header — stage 3 identified but substage (a, b, or unspecified) not definedAlways submit N18.30 (all 6 characters) when chronic kidney disease is documented as stage 3 and the provider has not specified stage 3a or 3b.
Clinical Context: Substage Matters — Query Before Defaulting to .30
ICD-10-CM N18.30 captures CKD stage 3 when the documentation does not distinguish between stage 3a (GFR 45-59) and stage 3b (GFR 30-44). Before defaulting to N18.30, check the lab values: if the GFR is documented and falls clearly in the 3a or 3b range, a CDI query to the provider may allow use of the more specific N18.31 or N18.32 codes. Under current CMS-HCC v28 mapping, none of the three stage 3 codes carry HCC payment weight, but substage specificity strengthens documentation integrity and positions the record accurately if disease progresses.
Code Classification
ICD-10-CM Diagnosis Code — wRVU, assistant-at-surgery payable status, and global period fields are not applicable to ICD-10-CM diagnosis codes. For associated procedures performed in the inpatient or outpatient setting, refer to the CPT Procedural Crosswalk and ICD-10-PCS Crosswalk sections below.
🔍 Code Description
[ICD-10-CM] N18.30 classifies chronic kidney disease (CKD), stage 3, unspecified — a moderate reduction in kidney function defined by a glomerular filtration rate (GFR) of 30-59 mL/min/1.73 m² that persists for three or more months, in which the provider has not specified or documented whether the stage is 3a or 3b.1,2
CKD results from progressive, irreversible structural or functional loss of nephron mass, leading to impaired filtration, fluid-electrolyte regulation, acid-base balance, and endocrine function (including erythropoietin and vitamin D production).2 At stage 3, patients are at elevated risk for cardiovascular disease, anemia, metabolic acidosis, secondary hyperparathyroidism, and accelerating progression toward stage 4 or end-stage renal disease (ESRD).2,3 The most common underlying etiologies include diabetic nephropathy, hypertensive nephrosclerosis, and glomerulonephritis.3
🌳 Code Tree / Hierarchy
N18 Chronic kidney disease (CKD) ❌ Non-billable
│
├── N18.1 Chronic kidney disease, stage 1 ✅ Billable
├── N18.2 Chronic kidney disease, stage 2 (mild) ✅ Billable
│
├── N18.3 Chronic kidney disease, stage 3 (moderate) ❌ Non-billable
│ │
│ ├── N18.30 Chronic kidney disease, stage 3 unspecified ◀ THIS CODE ✅ Billable
│ ├── N18.31 Chronic kidney disease, stage 3a ✅ Billable
│ └── N18.32 Chronic kidney disease, stage 3b ✅ Billable
│
├── N18.4 Chronic kidney disease, stage 4 (severe) ✅ Billable
├── N18.5 Chronic kidney disease, stage 5 ✅ Billable
├── N18.6 End stage renal disease ✅ Billable
└── N18.9 Chronic kidney disease, unspecified ✅ Billable
Push for Substage Specificity Before Using .30
GFR values in the medical record often distinguish 3a (GFR 45-59) from 3b (GFR 30-44) without a provider query. If the most recent GFR clearly places the patient in one substage, consider a CDI query to the provider. Using [[N18.31]] or N18.32 documents greater clinical precision and future-proofs the record for RAF tracking if CMS adds HCC mapping for substages in a future model year.
✅ Includes
The following clinical terms and scenarios map to N18.30 when documented:
- Chronic kidney disease, stage 3, moderate — substage not specified by provider
- CKD 3 NOS (not otherwise specified)
- Moderate CKD with GFR 30-59 mL/min/1.73 m² and no substage designation in the documentation
- CKD with persistent albuminuria and GFR in the stage 3 range, etiology documented separately (diabetic, hypertensive, or other)
❌ Excludes
Excludes 1 — Cannot Be Coded Simultaneously with N18.30
| Code | Description | Note |
|---|---|---|
| N18.9 | Chronic kidney disease, unspecified | Mutually exclusive — once a stage is documented, N18.9 cannot be used; the staged code replaces it entirely |
Excludes 1 Violation Risk
Excludes 2 — May Be Coded in Addition if Separately Present
| Code | Description | Note |
|---|---|---|
| N/A for formal Excludes 2 — see “Code First” and “Use Additional Code” instructions below |
"Code First" and "Use Additional Code" Instructions
ICD-10-CM tabular instructions at the N18 category level require the following sequencing rules:1
- Code first any associated diabetic CKD: E08.22, E09.22, E10.22, E11.22, E13.22
- Code first any associated hypertensive CKD: I12.- (hypertensive CKD) or I13.- (hypertensive heart and CKD)
- Use additional code to identify associated cachexia: E88.A
- Use additional code to identify kidney transplant status if applicable: Z94.0
📋 Clinical Overview
CKD Stage 3 Substage Comparison
Accurate sub-staging at stage 3 requires knowing the GFR range. The table below helps distinguish when N18.30 is appropriate vs. when a more specific code should be used.
| Feature | N18.30 — Stage 3 Unspecified | N18.31 — Stage 3a | N18.32 — Stage 3b |
|---|---|---|---|
| GFR Range | 30-59 (substage not documented) | 45-59 mL/min/1.73 m² | 30-44 mL/min/1.73 m² |
| Kidney Function | Moderate reduction, NOS | Mildly to moderately reduced | Moderately to severely reduced |
| Cardiovascular Risk | Elevated | Elevated | Higher than 3a |
| Progression Risk | Moderate | Lower within stage 3 | Higher within stage 3 |
| CMS-HCC v28 Mapping | ❌ No HCC | ❌ No HCC | ❌ No HCC |
| Best Used When | GFR not clearly 3a or 3b in documentation | GFR 45-59 confirmed or provider documents 3a | GFR 30-44 confirmed or provider documents 3b |
CDI Query Trigger — Substage Specificity
When lab data shows a GFR clearly within either the 45-59 or 30-44 range but the provider documents only “CKD stage 3” without further substage notation, initiate a CDI query asking the provider to specify stage 3a or 3b. This improves documentation quality and precision at no additional patient risk.
Manifestations & Symptom Burden
Common manifestations associated with CKD stage 3 that should be separately coded when documented:
- Anemia of chronic kidney disease: Reduced erythropoietin production; code with D63.1 — Anemia in chronic kidney disease, and N18.30 as the underlying condition
- Metabolic acidosis: Impaired acid excretion; code with E87.2 — Acidosis, when documented
- Secondary hyperparathyroidism: Phosphate retention and reduced active vitamin D; code with E21.1 — Secondary hyperparathyroidism, NEC
- Hypertension: Extremely common comorbidity/driver; sequence I12.- or I13.- before N18.30 per instructional notes
Coding Manifestations
Always code documented manifestations separately to capture full patient complexity for DRG accuracy. Key manifestation codes to consider:
- D63.1 — Anemia in chronic kidney disease
- E87.2 — Acidosis
- E21.1 — Secondary hyperparathyroidism, not elsewhere classified
- Z94.0 — Kidney transplant status (if applicable)
💰 HCC Risk Adjustment (CMS-HCC v28)
| Field | Detail |
|---|---|
| CMS-HCC Model Version | v28 (Fully operative as of January 1, 2026) |
| HCC Assignment | ❌ Not HCC-Mapped |
| HCC Category | N/A — CKD stages 1-3 are non-payment HCCs under v28 |
| RAF Coefficient | N/A — No RAF contribution |
N18.30 does not map to a payment HCC under CMS-HCC v28 and therefore does not contribute to the patient’s risk adjustment factor (RAF) score.4
Progression Monitoring — Upgrade if Supported
Although N18.30 carries no RAF weight, documenting CKD stage accurately is essential for longitudinal tracking. If the patient progresses to stage 4 (GFR 15-29), the code upgrades to N18.4, which maps to HCC 330 under v28 and adds significant RAF weight. Coders and CDI specialists should flag any GFR trending toward stage 4 to prompt timely provider documentation of progression.
🏥 MS-DRG Assignment
MDC 11 — Diseases and Disorders of the Kidney & Urinary Tract
| DRG | Title | Est. Relative Weight* |
|---|---|---|
| DRG 682 | Renal Failure with MCC | ~2.68 |
| DRG 683 | Renal Failure with CC | ~1.48 |
| DRG 684 | Renal Failure without CC/MCC | ~0.97 |
Approximate. Verify against IPPS FY2026 Final Rule Table 5.
Sequencing and Complications
When N18.30 is the principal diagnosis (reason for admission after study), the case groups to the DRG 682/683/684 triplet within MDC 11. N18.30 itself does not carry CC or MCC status as a secondary diagnosis — it will not elevate the DRG of another principal diagnosis. To achieve DRG 682 (with MCC) or DRG 683 (with CC), qualifying secondary diagnoses such as sepsis, respiratory failure, or other MCCs/CCs must be present and documented. Common secondary diagnoses that may affect DRG tier include hypertensive crisis, fluid and electrolyte disorders, anemia requiring transfusion, and acute-on-chronic kidney disease.
🔗 Related ICD-10-CM Codes
CKD Stage Progression Variants
| Code | Description |
|---|---|
| N18.1 | Chronic kidney disease, stage 1 |
| N18.2 | Chronic kidney disease, stage 2 (mild) |
| N18.30 | Chronic kidney disease, stage 3 unspecified ← This Code |
| N18.31 | Chronic kidney disease, stage 3a |
| N18.32 | Chronic kidney disease, stage 3b |
| N18.4 | Chronic kidney disease, stage 4 (severe) |
| N18.5 | Chronic kidney disease, stage 5 |
| N18.6 | End stage renal disease |
| N18.9 | Chronic kidney disease, unspecified |
CKD With Underlying Etiology — Code First Codes
| Code | Description |
|---|---|
| I12.9 | Hypertensive chronic kidney disease with stage 1 through stage 4 CKD, or unspecified CKD |
| I13.10 | Hypertensive heart and chronic kidney disease without heart failure, with stage 1-4 or unspecified CKD |
| E11.22 | Type 2 diabetes mellitus with diabetic chronic kidney disease |
| E10.22 | Type 1 diabetes mellitus with diabetic chronic kidney disease |
🛠️ Commonly Associated CPT Codes (Nephrology / Inpatient)
Inpatient and Outpatient Setting Context
CKD stage 3 is frequently managed in both nephrology outpatient office visits and inpatient settings. The CPT codes below reflect services commonly associated with this diagnosis across care settings. In the profee (professional fee) setting, Modifier -26 applies when the physician provides only the professional component of a technical procedure.
| CPT Code | Description | Profee Coding Notes |
|---|---|---|
| 99213 | Office/outpatient E/M, established patient, moderate complexity | Most common outpatient visit level for CKD management; document MDM or time |
| 99214 | Office/outpatient E/M, established patient, moderate-high complexity | Appropriate when managing multiple CKD comorbidities with new labs or medication changes |
| 50200 | Renal biopsy, percutaneous, needle | Used to determine CKD etiology (e.g., confirm diabetic vs. IgA nephropathy); requires -26 for interpretation only |
| 90935 | Hemodialysis procedure, single evaluation by physician | If stage 3 patient requires emergent or initiation HD; per-session professional billing |
| 90945 | Dialysis procedure (non-ESRD) with one evaluation | Applicable if acute intervention required in stage 3 |
| 36800 | Insertion of cannula for hemodialysis | For vascular access planning when approach to ESRD anticipated |
NCCI Bundling Considerations
- E/M codes (99213, 99214) billed on the same date as a procedure (e.g., renal biopsy 50200) require Modifier -25 on the E/M to confirm a separately identifiable evaluation and management service is documented in the record.
- Renal biopsy (50200) and imaging guidance (76942 ultrasound or 77002 fluoroscopic) — imaging guidance is typically separately reportable but verify payer-specific bundling policies.
🔬 ICD-10-PCS Crosswalk (Inpatient Procedures)
When N18.30 is an inpatient diagnosis, these PCS codes are relevant for associated inpatient procedures.
| PCS Section | Body System | Root Operation | Clinical Application |
|---|---|---|---|
| 5 (Extracorporeal or Systemic Assistance and Performance) | A (Physiological Systems) | 1 (Performance) | Hemodialysis: 5A1D00Z (single) or 5A1D60Z (multiple) — for inpatient HD initiated due to acute decompensation of CKD |
| 0 (Medical and Surgical) | T (Urinary System) | B (Excision) | Percutaneous renal biopsy: 0TB03ZX — diagnostic excision of kidney, percutaneous approach, to determine CKD etiology |
| 0 (Medical and Surgical) | T (Urinary System) | Y (Transplantation) | Kidney transplant, right or left allogeneic open: 0TY00Z0 / 0TY10Z0 — for advanced CKD approaching ESRD |
💊 Coding Scenarios and Examples
Scenario 1 — Inpatient: CKD Stage 3 as Reason for Admission with Fluid Overload
Clinical Vignette: A 67-year-old male with a history of type 2 diabetes and hypertension presents with progressive lower extremity edema and dyspnea on exertion over five days. Labs reveal a GFR of 42 mL/min/1.73 m², serum creatinine 2.1 mg/dL, and BUN 38. The attending nephrologist documents “CKD stage 3, moderate, due to diabetic nephropathy; admitted for acute fluid overload management.” Echocardiogram shows preserved ejection fraction with no acute systolic dysfunction.
Principal Diagnosis:
- E11.22 — Type 2 diabetes mellitus with diabetic chronic kidney disease (Code first per ICD-10-CM tabular instruction at N18 — diabetic CKD drives sequencing)
Secondary Diagnoses:
- N18.30 — Chronic kidney disease, stage 3 unspecified (Sequenced after E11.22 per “Code First” tabular note)
- I10 — Essential hypertension (Documented comorbidity)
- R60.0 — Localized edema (Presenting symptom — lower extremity edema)
MS-DRG Assignment: Without a CC or MCC secondary diagnosis upgrading the case, this groups to DRG 684. If metabolic acidosis or anemia requiring transfusion are also documented, a qualifying secondary diagnosis may push to DRG 683.
Scenario 2 — Inpatient: Sequencing Challenge — Hypertensive CKD
Clinical Vignette: A 72-year-old female is admitted for uncontrolled hypertension with hypertensive urgency. Her problem list documents CKD stage 3 (GFR 51), and labs on admission confirm creatinine 1.9 mg/dL. The attending documents “hypertensive chronic kidney disease, CKD stage 3 — admission for BP management.” No heart failure is documented.
Principal Diagnosis:
- I12.9 — Hypertensive chronic kidney disease with stage 1 through stage 4 CKD, or unspecified CKD (Correct — when hypertension and CKD coexist, I12.- is the combination code; do NOT separately code I10)
Secondary Diagnoses:
- N18.30 — Chronic kidney disease, stage 3 unspecified (Required — tabular instruction at I12 states “use additional code to identify stage of CKD”)
MS-DRG Assignment: I12.9 + N18.30 groups under MDC 05 (Circulatory) or MDC 11 depending on principal. Verify grouper output — hypertensive CKD may route to MDC 05 DRG 304/305 (Hypertension) or MDC 11 depending on the grouper logic path.
Scenario 3 — CDI Query: Substage Specificity for N18.30
Clinical Vignette: A 58-year-old male is seen in nephrology follow-up. The problem list states “CKD stage 3” with no further specification. Lab results from last month show GFR = 38 mL/min/1.73 m². The encounter note reads: “CKD stage 3, stable, continue dietary restrictions, recheck in 3 months.” No substage is documented.
Action / Outcome: The GFR of 38 falls squarely in the stage 3b range (30-44 mL/min/1.73 m²). The coder should not independently assign stage 3b — the provider must document it. A CDI query should be submitted asking: “The patient’s most recent GFR of 38 mL/min/1.73 m² corresponds to CKD stage 3b (GFR 30-44). Can you please clarify whether the patient’s CKD is stage 3a or stage 3b to support the most accurate coding?”
Query Response: Provider updates the note to state: “CKD stage 3b based on current GFR of 38.”
Corrected ICD-10-CM Coding:
- N18.32 — Chronic kidney disease, stage 3b (Updated from N18.30 based on provider clarification)
- I10 — Essential hypertension (Comorbidity; note: if hypertensive CKD relationship is documented, use I12.9 + N18.32 instead)
⚠️ Coding Pitfalls and Tips
| Pitfall or Tip | |
|---|---|
| ❌ | Coding N18.9 alongside N18.30. N18.9 is an Excludes 1 condition to N18.30. When stage 3 is documented, N18.9 cannot also be reported. The staged code entirely replaces the unspecified code. |
| ❌ | Failing to sequence the “Code First” code. When CKD is due to diabetes or hypertension, the diabetic CKD code (e.g., E11.22) or hypertensive CKD code (e.g., I12.9) must be sequenced before N18.30. Coding N18.30 as principal when a combination code applies is a sequencing error. |
| ❌ | Using N18.30 when the GFR clearly supports substage specificity. If documentation or lab data allows for CDI clarification of stage 3a or 3b, do not default to N18.30 when the more specific N18.31 or N18.32 can be supported. |
| ✅ | Always code documented manifestations separately. Anemia of CKD (D63.1), secondary hyperparathyroidism (E21.1), and metabolic acidosis (E87.2) should be coded when documented — these capture true clinical complexity and may qualify as CC or MCC diagnoses. |
| ✅ | Initiate a CDI query when GFR supports substage. If labs show GFR in the 45-59 or 30-44 range and only “CKD stage 3” is documented, query the provider to specify 3a or 3b for maximum documentation precision and future risk adjustment readiness. |
| ✅ | Monitor for progression to stage 4 at each encounter. If GFR is trending toward or into the 15-29 range, flag for the provider. Stage 4 (N18.4) maps to HCC 330 under CMS-HCC v28, which carries significant RAF weight — accurate upgrades directly impact risk adjustment payment. |
📚 Sources
- CMS/NCHS. ICD-10-CM Official Guidelines for Coding and Reporting, FY2026. Section I.C.14.a — Chronic kidney disease (CKD).
- National Kidney Foundation. KDIGO 2024 CKD Clinical Practice Guideline Update. Kidney International Supplements.
- Levey AS, Coresh J. (2012). Chronic kidney disease. The Lancet, 379(9811), 165-180. (Source for CKD pathophysiology, GFR staging, and comorbidity burden at stage 3.)
- CMS. 2025-2026 Medicare Advantage Risk Adjustment — CMS-HCC Model v28 ICD-10-CM Mappings. (CKD stages 1-3 non-payment HCC status confirmed.)
- CMS. IPPS Final Rule FY2026 — MS-DRG Definitions Manual v43.1. MDC 11 logic tables; DRG 682/683/684 Renal Failure triplet; N18.30 in diagnostic grouper listing.
- AAPC. ICD-10-CM Code N18.30 — Chronic kidney disease, stage 3 unspecified. aapc.com/codes/icd-10-codes/N18.30.