A patient’s creatinine spikes, the physician writes “AKI,” and your coder picks N17.9. Weeks later, the payer denies the claim for lack of clinical support. That is a common story in billing offices, and each lost AKI claim cuts into revenue you already earned. This guide gives you the right AKI ICD 10 code, the documentation behind it, and the fixes that keep kidney claims paid.
TL;DR
- The AKI ICD 10 code is N17.9 (Acute kidney failure, unspecified).
- Use N17.0, N17.1, N17.2, or N17.8 when the provider documents a specific type.
- AKI, acute renal failure, and acute kidney failure all map to category N17.
- ICD-10-CM has no AKI stage codes, so KDIGO stages support the diagnosis but never change the code.
- Code a resolved AKI with Z87.448, not N17.9.
- For AKI on CKD, report both N17.x and N18.x.
- The N17 codes carry no changes for FY2027.
What Is the ICD-10 Code for AKI?
The ICD-10-CM code for acute kidney injury is N17.9, Acute kidney failure, unspecified. It is a billable code in category N17, within Chapter 14 (N00-N99). Coders use N17.0 through N17.8 when the provider documents the specific type, such as acute tubular necrosis.
Category N17 also carries important instructional notes. First, it tells you to code the associated underlying condition, such as sepsis or dehydration. Second, an Excludes1 note blocks posttraumatic renal failure (T79.5). Third, an Excludes2 note lets you report traumatic kidney injury (S37.0-) alongside N17 when both conditions exist. You can confirm each note in the official CDC ICD-10-CM code files.
Acute Kidney Injury ICD-10 Codes: Complete N17 List
The N17 category holds five billable codes. Each one matches a documented type of acute kidney failure.
| Code | Description | Use When the Provider Documents | Severity (MS-DRG) |
|---|---|---|---|
| N17.0 | Acute kidney failure with tubular necrosis | Acute tubular necrosis (ATN) | MCC |
| N17.1 | Acute kidney failure with acute cortical necrosis | Cortical necrosis | MCC |
| N17.2 | Acute kidney failure with medullary necrosis | Medullary or papillary necrosis | MCC |
| N17.8 | Other acute kidney failure | Another specified type | CC |
| N17.9 | Acute kidney failure, unspecified | AKI or ARF with no type stated | CC |
Specificity directly affects payment. For example, when a nephrologist documents ATN, N17.0 counts as a major complication (MCC), while N17.9 counts only as a CC. As a result, a missed specificity query can drop an inpatient stay from DRG 682 to DRG 683.
Is AKI the Same as Acute Renal Failure in ICD-10?
Yes. Acute kidney injury, acute renal failure, and acute kidney failure all point to category N17. AKI is the modern clinical term, while the official code title still uses the phrase “acute kidney failure.”
In practice, providers use these terms interchangeably in the same chart. So a coder who sees “ARF” in the history and “AKI” in the assessment still reports one N17 code, not two.
However, “renal insufficiency” alone does not equal AKI. The ICD-10-CM index sends it to N28.9 (Disorder of kidney and ureter, unspecified). So when a provider writes “acute renal insufficiency,” send a query to confirm whether they mean AKI.
When Should You Use N17.9 (AKI Unspecified)?
N17.9 fits when the provider documents AKI or acute renal failure without naming a type. It also fits most outpatient and post-acute visits, where no one has confirmed ATN or necrosis.
Still, watch for these red flags before you submit N17.9:
- Nephrology notes mention “ATN” or “muddy brown casts.” In that case, N17.0 likely applies.
- An ICU patient on dialysis carries only an unspecified code.
- A home health agency keeps reporting N17.9 after the AKI resolved. The correct code is then Z87.448.
In short, N17.9 is a valid code, but it should reflect the record, not a coder’s shortcut.
Are There ICD-10 Codes for AKI Stage 1, 2, or 3?
No. ICD-10-CM has no stage-specific AKI codes. KDIGO stages 1 through 3 describe clinical severity, but you still assign N17.x based on the documented type.
This point matters because some online guides claim that N17.1 means “stage 1” or that an N17.3 code exists. Both claims are wrong. N17.1 describes acute cortical necrosis, and N17.3 does not exist. Chronic kidney disease, by contrast, does have stage codes (N18.1 through N18.6).
What Is the ICD-10 Code for History of AKI?
Use Z87.448, Personal history of other diseases of urinary system, when the AKI has resolved and the patient no longer receives treatment for it.
The difference comes down to active care. If the provider still monitors labs, adjusts medications, or manages fluids for the kidney injury, code N17.x. Once the condition resolves, switch to Z87.448. Follow-up visits and home health admissions often get this wrong.
How Do You Code AKI on CKD?
When a provider documents “acute on chronic kidney failure,” code both conditions. Report N17.x for the acute injury and N18.x for the CKD stage. Also add Z99.2 when the patient depends on dialysis.
Hypertension adds one more rule. ICD-10-CM presumes a link between hypertension and CKD, which sends you to I12 or I13. That presumption does not cover AKI, however, so you still code the AKI separately.
Example: A hypertensive patient with CKD stage 3b develops AKI. Code I12.9, N18.32, and N17.9, then sequence them based on the setting and the reason for the encounter.
ICD-10 Codes Often Confused With AKI
Several nearby codes look similar but describe different conditions. Use this table to avoid common mix-ups.
| Code | Description | Why It Differs From AKI |
|---|---|---|
| N19 | Unspecified kidney failure | Acuity not stated; query the provider |
| R94.4 | Abnormal results of kidney function studies | A lab finding, not a diagnosis |
| N99.0 | Postprocedural (acute) (chronic) kidney failure | Needs a documented link to a procedure |
| O90.49 | Other postpartum acute kidney failure | Obstetric codes take priority |
| P96.0 | Congenital renal failure | Used for newborns |
| N14.11 | Contrast-induced nephropathy | Pair it with an adverse effect code |
| S37.0- | Injury of kidney | Traumatic cause |
How Do You Sequence AKI With Sepsis, Dehydration, and Drugs?
Sequencing depends on the cause and the setting. The FY2027 ICD-10-CM Official Guidelines set the rules for each scenario below.
AKI With Sepsis
Code the systemic infection first, such as A41.9. Then add R65.20 for severe sepsis when the provider links the AKI to sepsis as organ dysfunction. Finally, report N17.x for the kidney injury.
AKI With Dehydration
Code both E86.0 and N17.9. Then choose the principal diagnosis based on the circumstances of admission and the guideline for two or more diagnoses that equally meet the definition.
Drug- or Contrast-Induced AKI
Report N17.x, or N14.11 for contrast nephropathy. Then add the adverse effect code for the drug, such as T50.8X5A for a diagnostic contrast agent. Likewise, NSAIDs, vancomycin, and lithium each have their own adverse effect codes.
Postprocedural AKI
Use N99.0 with N17.x only when the provider clearly documents that the procedure caused the kidney injury.
What Documentation Supports an AKI Diagnosis?
Payers often test AKI claims against the KDIGO criteria. According to KDIGO, AKI meets the definition when any one of these occurs:
- Serum creatinine rises by 0.3 mg/dL or more within 48 hours
- Serum creatinine reaches 1.5 times baseline or more within 7 days
- Urine output falls below 0.5 mL/kg/h for 6 hours
Strong charts also include these details:
- Baseline creatinine, peak value, and trend
- Urine output records
- Suspected cause (prerenal, intrinsic, or postrenal)
- Treatment, such as IV fluids, held nephrotoxins, or dialysis
- Acute versus chronic status
KDIGO also released a 2026 AKI and Acute Kidney Disease guideline draft for public review. It frames kidney injury as a continuum and adds structural biomarkers to the criteria. Even so, coders must always assign codes from provider documentation, never from lab values alone.
Common AKI Denials and How to Fix Them
Most AKI denials follow a predictable pattern. Fortunately, each one has a clear fix.
| Denial Reason | How to Fix It |
|---|---|
| Clinical validation: does not meet AKI criteria | Document the baseline and KDIGO rise, then cite them in the appeal |
| N17.9 billed after the AKI resolved | Switch to Z87.448 |
| Missing or wrong POA indicator | Assign POA from documentation at admission |
| AKI coded from lab values alone | Send a compliant provider query |
| CKD stage missing on AKI on CKD | Add N18.x with the correct stage |
For a step-by-step appeal process, see our Medical Denial Management Playbook.
Coding AKI by Care Setting
Inpatient
Hospitals feel the biggest AKI impact because of CC and MCC status. A single AKI code can move a claim into a higher-weighted DRG, so payers audit it closely as a secondary diagnosis.
To protect these claims, assign an accurate POA indicator for every AKI code. Then make sure the progress notes and the discharge summary both mention the AKI, its cause, and its treatment. When the two documents conflict, query the attending physician before you finalize the claim.
Home Health (PDGM)
Agencies must separate active AKI from history. Before you use N17.x as a primary diagnosis, check its status in the current PDGM grouper. Our Home Health Billing Guide covers PDGM rules in detail.
Hospice
AKI usually appears as a related or contributing condition rather than the terminal diagnosis. Therefore, confirm your principal diagnosis against the list of unacceptable hospice principal diagnosis codes.
Behavioral Health
Lithium can injure the kidneys. When the prescriber documents lithium-associated AKI, code N17.x along with the lithium adverse effect code, and keep the medication notes in the record.
Get Your Kidney Claims Paid the First Time
Right On Time Billing’s certified coders review AKI, CKD, and renal claims before they reach the payer. As a result, you catch specificity gaps and missing documentation early. Book a free coding audit and protect the revenue your team already earned.
Related Guides and Resources
- Shortness of Breath ICD-10 Code (R06.02)
- Anemia ICD-10 Codes: D64.9 Guide
- NSTEMI ICD-10 Codes Explained
- Renal Ultrasound CPT Code: 2026 Guide
- Medical Coding Audits 2026
- Home Health Denial Codes and RTP Guide
- Hospice Billing Guide 2026
- Medical Coding Services
- Denial Management Services
Frequently Asked Questions
What is the ICD-10 code for AKI?
The ICD-10 code for AKI is N17.9, Acute kidney failure, unspecified. Use N17.0 through N17.8 when the provider documents a specific type.
Is N17.9 a billable code?
Yes. N17.9 is a billable, specific code, and it remains valid for FY2027.
What is the ICD-10 code for acute renal failure?
Acute renal failure uses the same code as AKI, N17.9, unless the provider documents a specific type.
Is there an ICD-10 code for AKI stage 3?
No. ICD-10-CM does not include AKI stage codes. You assign N17.x based on type, not stage.
What is the ICD-10 code for history of AKI?
Use Z87.448 when the AKI has resolved and no longer requires treatment.
Can you code N17.9 and N18 together?
Yes. When a patient has AKI on CKD, report both N17.x and N18.x with the correct CKD stage.
Is N17.9 a CC or MCC?
N17.9 is a CC. In contrast, N17.0, N17.1, and N17.2 are MCCs, so specific documentation can raise the DRG.
