Kidney Failure ICD-10 Coding Guide: Complete 2026 Reference for Medical Coders

 If you work in medical billing, nephrology coding, or clinical documentation, you already know that kidney failure ICD-10 coding is one of the most scrutinized areas in the entire ICD-10-CM system. Claim denials, compliance audits, and Medicare reimbursement reviews frequently target renal failure codes  and for good reason. The codes are nuanced, the clinical distinctions matter enormously, and even a single digit of difference can mean thousands of dollars in under- or over-reporting.

This kidney failure ICD-10 coding guide is designed to give you everything you need in one place: every relevant code, official coding guidelines, real-world scenarios, common errors, and expert tips to keep your documentation bulletproof.

What Is ICD-10 and Why Does It Matter for Kidney Failure?

The ICD-10-CM (International Classification of Diseases, 10th Revision, Clinical Modification) is the standardized diagnostic coding system used across all U.S. healthcare settings for inpatient and outpatient billing. The Centers for Medicare & Medicaid Services (CMS) requires ICD-10-CM codes on every claim submitted for reimbursement.

For kidney disease specifically, ICD-10-CM assigns codes based on two critical variables:

• The timeline  Is the kidney failure acute (sudden onset) or chronic (progressive, long-term)?
• The severity   For chronic kidney disease (CKD), what stage is the patient in based on GFR?

Getting these two variables right is the entire foundation of accurate renal failure ICD-10 coding. Everything else builds from there.

Kidney failure codes live primarily in Chapter 14: Diseases of the Genitourinary System (N00–N99), with the core kidney failure codes concentrated between N17 and N19.

Part 1: Acute Kidney Failure ICD-10 Codes   The N17 Category

Acute kidney failure (AKF), also called acute kidney injury (AKI), refers to a sudden and often reversible loss of renal function. It develops over hours to days and requires rapid clinical intervention. In ICD-10-CM, acute kidney failure codes fall under category N17, with subcategories based on the specific pathological mechanism involved.

N17.0  Acute Kidney Failure with Tubular Necrosis

Acute tubular necrosis (ATN) is the single most common cause of intrinsic AKI. It occurs when nephrotoxic agents — contrast dye, aminoglycoside antibiotics, NSAIDs, cisplatin — or prolonged ischemia destroy the renal tubular epithelial cells.

When to use it: Assign N17.0 whenever the treating physician explicitly documents "acute tubular necrosis" or "ATN" in the context of AKI. Never default to the unspecified code N17.9 when this level of clinical detail is available.

N17.1  Acute Kidney Failure with Acute Cortical Necrosis

This rare but life-threatening form of AKI involves necrosis of the renal cortex, typically sparing the medulla. It is most often associated with obstetric emergencies such as placental abruption and septic abortion, as well as hemolytic uremic syndrome (HUS) and severe hypotension.

N17.2  Acute Kidney Failure with Medullary Necrosis

Also referred to as renal papillary necrosis in the acute phase, medullary necrosis is associated with analgesic overuse, diabetes mellitus, sickle cell disease, and urinary obstruction. When the physician documents medullary or papillary necrosis alongside AKI, this is the appropriate code.

N17.8  Other Acute Kidney Failure

Use this code for documented forms of AKI that do not fit into the tubular, cortical, or medullary categories above. Always support the selection of this code with clear physician documentation.

N17.9  Acute Kidney Failure, Unspecified

This is the fallback code when AKI is documented but no specific pathological subtype is identified. While frequently used, N17.9 is also a major CDI query trigger. If lab trends and clinical notes suggest a more specific etiology, query the physician before assigning the unspecified code.

ICD-10-CM Coding Rule: AKI + CKD = Dual Coding

One of the most important rules in the kidney failure ICD-10 coding guide is this: when a patient has both AKI and pre-existing CKD, you must assign codes for both conditions. The ICD-10-CM Official Guidelines for Coding and Reporting explicitly state that acute kidney failure superimposed on chronic kidney disease requires codes from both the N17 and N18 categories. Sequencing (which is the principal diagnosis) depends on the circumstances of admission and the focus of treatment.

Part 2: Chronic Kidney Disease ICD-10 Codes — The N18 Category

Chronic kidney disease (CKD) is a progressive, irreversible decline in kidney function lasting more than three months. ICD-10-CM stages CKD using the Kidney Disease: Improving Global Outcomes (KDIGO) framework, which is based on the GFR (Glomerular Filtration Rate). This staging system directly determines which chronic kidney disease ICD-10 code is assigned.

N18.1 — Chronic Kidney Disease, Stage 1

GFR ≥ 90 mL/min/1.73m² with evidence of kidney damage such as persistent proteinuria, hematuria, or structural abnormality. The GFR is normal or elevated, but there is documented kidney pathology. Stage 1 CKD is frequently undercoded because providers overlook it in the presence of normal creatinine.

N18.2 — Chronic Kidney Disease, Stage 2 (Mild)

GFR 60–89 mL/min/1.73m² with kidney damage markers present. Usually asymptomatic and discovered incidentally during routine labs. This is a critical stage for early intervention to slow CKD progression.

N18.31 — Chronic Kidney Disease, Stage 3a

GFR 45–59 mL/min/1.73m². This code was added in the ICD-10-CM FY2022 update, splitting the former single Stage 3 code into two more specific subcategories. Coders must verify their encoder software reflects this update.

N18.32 — Chronic Kidney Disease, Stage 3b

GFR 30–44 mL/min/1.73m². Stage 3b carries a significantly higher risk of CKD progression and cardiovascular complications than Stage 3a. The clinical and coding distinction between the two is important for risk stratification reporting.

N18.4 — Chronic Kidney Disease, Stage 4 (Severe)

GFR 15–29 mL/min/1.73m². At this stage, the nephrologist typically begins preparing the patient for renal replacement therapy — whether hemodialysis, peritoneal dialysis, or transplant evaluation. Accurate coding at this stage is critical for quality measure reporting under CMS programs.

N18.5 — Chronic Kidney Disease, Stage 5

GFR < 15 mL/min/1.73m². This indicates kidney failure in the absence of dialysis. Assign N18.5 — NOT N18.6 — when the patient has GFR below 15 but has not yet started chronic dialysis. This distinction is one of the most frequently confused pairs in nephrology coding.

N18.6 — End-Stage Renal Disease (ESRD)

N18.6 is one of the highest-stakes codes in the entire kidney failure ICD-10 coding guide. Assign this code when the patient has CKD Stage 5 AND is receiving chronic renal replacement therapy — hemodialysis, peritoneal dialysis, or following a kidney transplant.

Critical rule: Per ICD-10-CM guidelines, assign N18.6 in conjunction with Z99.2 (Dependence on renal dialysis) whenever the patient is dialysis-dependent. Omitting Z99.2 is one of the most cited coding errors in ESRD billing audits.

N18.9 — Chronic Kidney Disease, Unspecified

Use only when CKD is documented but no stage is available anywhere in the record. This should be a last resort. Before assigning N18.9, review GFR trends, nephrology consultation notes, lab values, and the patient's problem list. Assign N18.9 only after exhausting all documentation sources.

Part 3: Unspecified Kidney Failure — N19

N19 is assigned when the physician documents kidney failure but does not specify whether it is acute, chronic, or a combination, and there is no other documentation in the chart to support a more specific code.

This code should be used sparingly. Coders who find themselves regularly assigning N19 should view it as a documentation improvement opportunity. A concurrent query program targeting "renal failure NOS" or "kidney failure unspecified" can dramatically improve coding accuracy and revenue capture.

Part 4: Real-World Kidney Failure ICD-10 Coding Scenarios

Theory is essential, but coding happens in the real world. Here are five high-frequency clinical scenarios with correct code assignments.

Scenario 1: Acute Kidney Injury on Chronic Kidney Disease

A 68-year-old male with a history of CKD Stage 3b is admitted for AKI secondary to dehydration. Creatinine has doubled from baseline.

• N17.9  Acute kidney failure, unspecified (principal dx if reason for admission)
• N18.32   CKD Stage 3b (secondary)

Both codes are required per ICD-10-CM official guidelines.

Scenario 2: End-Stage Renal Disease on Hemodialysis

A 55-year-old female with ESRD presents for her routine hemodialysis session.

• N18.6   End-stage renal disease
• Z99.2   Dependence on renal dialysis

Z99.2 is always required as an additional code with N18.6 in dialysis-dependent patients.

Scenario 3: Type 2 Diabetes with CKD Stage 4

A 72-year-old male with Type 2 diabetes is seen by nephrology for worsening CKD Stage 4 attributed to diabetic nephropathy.

• E11.65   Type 2 diabetes mellitus with hyperglycemia and CKD
• N18.4   CKD Stage 4

ICD-10-CM assumes a causal relationship between diabetes and CKD when both are documented. The combination code E11.65 captures the diabetic etiology, but N18.4 must still be added to identify the stage.

Scenario 4: Hypertension with CKD

A 61-year-old female with hypertension and CKD Stage 3a is seen in a nephrology clinic.

• I12.9   Hypertensive chronic kidney disease with CKD Stage 1–4 or unspecified
• N18.31   CKD Stage 3a

Do NOT code hypertension (I10) and CKD separately. ICD-10-CM assumes a causal relationship and requires combination coding from category I12 or I13.

Scenario 5: Post-Transplant CKD

A 45-year-old male who received a kidney transplant three years ago now has biopsy-confirmed CKD Stage 2.

• N18.2   CKD Stage 2
• Z94.0   Kidney transplant status

A functioning transplant does not eliminate CKD. Both codes are required.

Part 5: Most Common Kidney Failure ICD-10 Coding Errors

CMS post-payment reviews and OIG work plans consistently flag the following errors in kidney failure coding:

Error 1  Defaulting to N18.9 when staging data is available. GFR values, nephrology notes, and clinical trends almost always support a staged CKD code.

Error 2   Omitting Z99.2 with N18.6. Every dialysis-dependent ESRD encounter requires Z99.2. No exceptions.

Error 3   Confusing N18.5 and N18.6. CKD Stage 5 without dialysis = N18.5. ESRD with dialysis = N18.6. Verify dialysis status before code assignment.

Error 4   Coding hypertension and CKD separately. Always use the I12/I13 combination codes when both conditions are documented together.

Error 5   Ignoring the AKI subtype. When ATN, cortical necrosis, or medullary necrosis is documented, assign the specific N17.0, N17.1, or N17.2. Never default to N17.9 with specific documentation available.

Part 6: Supporting Codes Frequently Used with Kidney Failure

ICD-10 Code	Description
Z99.2	Dependence on renal dialysis
Z94.0	Kidney transplant status
Z49.01	Encounter for fitting and adjustment of extracorporeal dialysis catheter
Z49.31	Encounter for adequacy testing of hemodialysis
E11.65	Type 2 DM with hyperglycemia and CKD
E10.65	Type 1 DM with hyperglycemia and CKD
I12.9	Hypertensive CKD with CKD Stage 1–4, unspecified
I13.10	Hypertensive heart and CKD without heart failure
R80.9	Proteinuria, unspecified
N04.9	Nephrotic syndrome, unspecified

Final Thoughts: Elevating Your Kidney Failure ICD-10 Coding Accuracy

Accurate kidney failure ICD-10 coding is not merely a billing exercise — it directly shapes risk adjustment scores, quality benchmarks, population health analytics, and Medicare reimbursement rates. Every code in this guide carries weight far beyond a claim form.

The most impactful steps you can take are straightforward: always push for documentation specificity, leverage CDI queries when staging or diagnosis type is unclear, and audit your ESRD encounters to ensure Z99.2 is never omitted. Keep this kidney failure ICD-10 coding guide bookmarked and revisit it every October when CMS releases annual ICD-10-CM updates — because in medical coding, what was accurate last year may be incomplete today.

Master these codes, and you will not only protect your organization from audit risk — you will ensure that every patient's clinical complexity is fully and accurately represented in the data.