ICD-10 Codes for Chronic Kidney Disease (N18.1–N18.6)

CKD is coded by stage — the N18 ladder

ICD-10-CM codes chronic kidney disease by the documented stage. The clinician stages CKD from kidney function (typically eGFR) and related findings; the coder's job is to match the stage written in the note to the right N18 code — not to derive a stage from lab values.

Two things to notice before going further. Plain N18.3 is no longer billable on its own — stage 3 requires a fifth character (next section). And N18.9 (unspecified) is the fallback when CKD is documented with no stage at all: valid, but a quick stage query almost always produces a better code. Search the lookup tool for the full family.

The stage 3 split: N18.30, N18.31, N18.32

Since the FY2021 code update, stage 3 is three codes, not one. Clinically, stage 3 spans eGFR 30–59, and the split mirrors the two bands clinicians already document: 3a (eGFR 45–59) codes to N18.31, 3b (eGFR 30–44) codes to N18.32, and a note that says only “CKD stage 3” lands on N18.30, stage 3 unspecified.

N18.30 is a legitimate code — but treating it as the everyday default gives away specificity that is usually sitting in the chart already. If the note says “stage 3” while the record clearly supports a substage, that's a query. What the coder should not do is assign 3a or 3b from the eGFR numbers alone: the stage is a clinical determination, and the provider's documentation is what supports the code.

Stage 5 vs. ESRD — and the Z99.2 dialysis rule

N18.5 and N18.6 sit next to each other on the ladder but mean different things. Stage 5 (N18.5) is the documented stage when kidney function has fallen to its lowest band but the provider hasn't called it end stage renal disease. N18.6 is for documented ESRD — typically the patient whose kidney failure is managed with chronic dialysis. The guidelines settle the overlap directly: if both a stage of CKD and ESRD are documented, assign only N18.6.

N18.6 also carries its own instruction: use an additional code to identify dialysis status — Z99.2 (dependence on renal dialysis) for the patient on chronic dialysis. The N18.6 + Z99.2 pair is the standard picture of a dialysis patient in ICD-10, and dropping the Z code is one of the quiet, recurring omissions in nephrology coding.

The combination trap: diabetic and hypertensive CKD

Diabetic CKD: the diabetes code leads

ICD-10's “with” convention presumes the link between diabetes and chronic kidney disease — when both appear in the record, they're coded as related unless the provider clearly states the CKD is unrelated to the diabetes (for example, by attributing it solely to another cause). The combination code follows the diabetes type, and each one instructs you to use an additional code to identify the stage (N18.1–N18.6). So diabetic CKD is always two codes, diabetes first:

Secondary and other diabetes types follow the same pattern (E08.22, E09.22, E13.22). One nearby distinction worth knowing: E11.21 is type 2 diabetes with diabetic nephropathy — kidney damage documented without chronic kidney disease. Once CKD is in the note, E11.22 plus the N18 stage is the specific combination. For the rest of the family — ophthalmic, neurologic, and circulatory complications — see our ICD-10 guide to diabetes codes.

Hypertensive CKD: the link is presumed

Hypertension plus CKD is the strongest presumption in ICD-10: the guidelines assume the causal relationship whenever both are present — no “due to” statement required. The code moves from I10 to category I12, chosen by stage severity, with the N18 stage added as a secondary code:

Reporting I10 and an N18.- code as two unrelated diagnoses understates the record and misses the required combination. The one exception: if the provider explicitly documents that the CKD is not related to the hypertension, code them separately. The full I10–I16 decision tree — heart involvement, crisis codes, secondary hypertension — is in our ICD-10 guide to hypertension.

Both diabetes and hypertension? Assign both pairings

The two presumptions stack. A patient with type 2 diabetes, hypertension, and CKD gets both combination codes — for example E11.22 and I12.9 — plus a single N18 stage code serving both. The guidelines don't dictate which combination code goes first; sequence according to the circumstances of the encounter. And when hypertensive heart disease is also documented, category I13 replaces I12, combining heart and kidney in one code:

One instruction rides along with I13: when heart failure is part of the picture (I13.0, I13.2), the guidelines call for an additional code from I50.- to identify the type of heart failure.

After a kidney transplant: Z94.0 — and the stage still counts

A kidney transplant doesn't necessarily restore full kidney function, and the guidelines address this head-on: post-transplant CKD is not, by itself, a transplant complication. When a transplant recipient has residual chronic kidney disease, code the documented N18.- stage and add Z94.0 (kidney transplant status). Coders sometimes hesitate to put a CKD stage on a transplanted patient — it feels like coding a problem the surgery fixed — but the stage describes the patient's current kidney function, transplanted or not.

The line to watch is complication language. If the provider documents transplant rejection (T86.11), failure (T86.12), or infection (T86.13), the encounter is coded with the complication code rather than the Z94.0 status code. And if it's unclear whether declining function in a transplanted kidney represents a complication, that's a query for the provider — not a coder's judgment call.

Common CKD coding mistakes

• Sequencing N18 first when diabetes or hypertension is documented. The code-first note under N18 puts the combination code (E11.22, I12.-, I13.-) ahead of the stage — N18 alone is rarely the whole answer.
• Coding I10 and N18.- as unrelated diagnoses. The hypertension–CKD link is presumed; the record needs I12.- (or I13.-) with the N18 stage secondary, unless the provider states the two are unrelated.
• Reporting N18.5 for a documented ESRD patient. When both a stage and ESRD are documented, N18.6 alone is correct — and chronic dialysis adds Z99.2.
• Defaulting to N18.30 without a query. Stage 3 unspecified is valid, but the 3a/3b detail usually exists in the chart and carries real specificity.
• Treating post-transplant CKD as a complication. Residual CKD after a transplant is coded N18.- plus Z94.0; the T86.1- complication codes require documented rejection, failure, or infection.

A worked example

Nearby traps: acute kidney injury and anemia in CKD

Acute kidney injury is not CKD. AKI codes to N17.- (for example N17.9, acute kidney failure, unspecified), and the two aren't interchangeable — one is an acute event, the other a chronic, staged disease. When AKI is superimposed on CKD, code both: the acute failure and the chronic stage each tell part of the story. Anemia in CKD runs the sequencing the other way: D63.1 (anemia in chronic kidney disease) carries a code-first note for the underlying CKD, so the N18 code — or the full diabetic or hypertensive chain ahead of it — precedes the anemia code. And CKD documented with no stage at all lands on N18.9 — codeable, but usually one query away from a stage-specific code.

What the note needs to document

• The stage — 1, 2, 3a, 3b, 4, 5 — or an explicit statement of ESRD
• Chronic dialysis dependence, which adds Z99.2
• Any diabetes and its type, which selects the E08–E13 combination code
• Any hypertension — or an explicit note that the CKD is unrelated to it
• Kidney transplant history (Z94.0) and whether any complication is documented

Frequently asked questions