N18.9: Chronic kidney disease, unspecified

The ICD-10-CM code for chronic kidney disease when the record documents CKD but does not state the stage.

Billable

FY2027

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At a glance

Code Family

N18: Chronic kidney disease (CKD).

Condition

Chronic kidney disease

Billable

Yes, valid for HIPAA covered transactions.

HCC Mapping (v28)

None. N18.9 carries no HCC. The codes for stage 3 through end stage renal disease carry HCC 326 through HCC 329.

DRG Grouping

As the principal diagnosis N18.9 groups to MS-DRG 682, 683 or 684, renal failure with MCC, with CC or without CC/MCC, in MDC 11 under the FY2027 MS-DRG v44 grouper. N18.9 carries no CC or MCC designation as a secondary diagnosis, per the FY2027 MS-DRG v44 CC and MCC lists.

Family Specificity

Nine billable codes structured on CKD stage. Only stage 3 and above carry risk adjustment weight.

Which N18 code do I assign?

The N18 family splits on the documented stage of chronic kidney disease, which clinical nephrology guidelines set against eGFR thresholds. The stage must come from provider documentation, and only the codes for stage 3 and above carry HCC weight under CMS-HCC v28.

When documentation says…

Code

CKD stage 2, eGFR 60 to 89

N18.2

Chronic kidney disease, stage 2 (mild). Stage 1, an eGFR of 90 or above, takes N18.1. Neither code maps to an HCC under CMS-HCC v28.

CKD stage 3a, eGFR 45 to 59

N18.31

Chronic kidney disease, stage 3a. Maps to HCC 329, CKD moderate, stage 3 except 3b. Stage 3 documented without a 3a or 3b qualifier takes N18.30, which maps to the same HCC.

CKD stage 3b, eGFR 30 to 44

N18.32

Chronic kidney disease, stage 3b. Maps to HCC 328, CKD moderate, stage 3b. The note must carry the 3b qualifier.

CKD stage 4, eGFR 15 to 29

N18.4

Chronic kidney disease, stage 4 (severe). Maps to HCC 327, CKD severe, stage 4.

CKD stage 5, eGFR below 15, no dialysis

N18.5

Chronic kidney disease, stage 5. Maps to HCC 326, chronic kidney disease, stage 5.

End stage renal disease, patient on dialysis

N18.6

End stage renal disease. Maps to HCC 326. Code Z99.2 additionally for dialysis dependence.

Chronic kidney disease, stage not stated

N18.9

Chronic kidney disease, unspecified. Used when CKD is documented but the stage is not specified or cannot be determined from the available clinical information. N18.9 carries no HCC.

Tabular notes

CODE FIRST

Category N18 carries a Code first note for any associated diabetic chronic kidney disease (E08.22, E09.22, E10.22, E11.22, E13.22) and hypertensive chronic kidney disease (the I12 and I13 codes). Under Guideline I.C.9.a.2, hypertension with chronic kidney disease is coded to category I12 unless the provider indicates the two are unrelated. When the hypertensive combination code is assigned, N18.9 or the stage specific N18 code is reported as an additional code.

USE ADDITIONAL

Category N18 carries its own Use additional code note, if applicable, for associated cachexia (E88.A) and kidney transplant status (Z94.0). A separate note sits at E11.22, type 2 diabetes mellitus with diabetic chronic kidney disease. It calls for an additional code to identify the stage of chronic kidney disease and names N18.1–N18.6. N18.9 falls outside that range. Where the stage is documented, add the stage specific N18 code.

FY2027: EFFECTIVE 1 OCTOBER 2026

N18.9 was valid in the FY2026 code set and is unchanged in the FY2027 update. The FY2027 codes and tabular addenda add, delete or revise no code or note in category N18.

Operational & financial impact

Why specificity matters beyond the chart: risk adjustment, DRG assignment and denial exposure all follow from which code is selected.

CMS-HCC v28 (PY2024+)

N18.9 does not map to an HCC. Chronic kidney disease coded without a stage yields no risk adjustment weight.

HCC 329, CKD moderate, stage 3 except 3b: N18.30 and N18.31.

HCC 328, CKD moderate, stage 3b: N18.32.

HCC 327, CKD severe, stage 4: N18.4.

HCC 326, chronic kidney disease, stage 5: N18.5 and N18.6.

In the v28 hierarchy, HCC 326 supersedes HCC 327, 328 and 329, and HCC 327 supersedes HCC 328 and 329.

WHERE SPECIFICITY IS LOST

N18.9 is the point at which the stage axis collapses. The record shows chronic kidney disease. The claim carries no HCC.

A coder may not assign a CKD stage from laboratory values without physician documentation. Where an eGFR value sits in the record and CKD is diagnosed, a CDI query to the provider is the route to a stage specific code.

V24 TO V28 TRANSITION

Under CMS-HCC v24, N18.30, N18.31 and N18.32 mapped to HCC 138, N18.4 to HCC 137, and N18.5 and N18.6 to HCC 136. N18.9 mapped to no HCC under v24 either. Under v28, stage 3 splits between HCC 328 for stage 3b and HCC 329 for the other stage 3 codes.

MS-DRG v44 (FY2027)

N18.9 carries no CC or MCC designation as a secondary diagnosis.

Under the FY2027 MS-DRG v44 lists, CMS Tables 6I and 6J, N18.4 and N18.5 are CCs and N18.6 is an MCC.

Medicare and commercial payers

N18.9 is a valid diagnosis code for Medicare claims.

For risk adjustment under Medicare Advantage, a code for stage 3 or higher is required to map to an HCC. N18.9 alone does not qualify.

Documentation checklist to support N18.9

Chart elements that support code selection and reduce specificity-driven denials.

A stated diagnosis of chronic kidney disease, rather than an abnormal creatinine or eGFR value on its own.

The CKD stage, either stated explicitly such as CKD stage 3a, or supported by eGFR documentation sufficient for the provider to derive the stage under KDIGO criteria.

Provider authorship of the stage. A coder may not assign a CKD stage from laboratory values without physician documentation.

A CDI query where the eGFR in the record supports a higher stage than the provider has documented.

Any coexisting hypertension, which directs the encounter to the I12.- or I13.- categories as the first listed code.

Any coexisting diabetes mellitus with chronic kidney disease, which is captured by a combination code such as E11.22.

Dialysis dependence, which supports Z99.2 alongside N18.6.

For inpatient discharges, confirmation of the stage where it is derivable from a documented eGFR with physician correlation.

FAQ

Is N18.9 billable?

Yes. N18.9 is a billable code and is valid for HIPAA covered transactions. It was valid in the FY2026 code set and is unchanged in the FY2027 update, effective 1 October 2026.

Does N18.9 map to an HCC?

No. N18.9 carries no HCC under CMS-HCC v28 and yields no risk adjustment weight. The stage specific codes N18.30, N18.31, N18.32, N18.4, N18.5 and N18.6 map to HCC 329, HCC 328, HCC 327 and HCC 326. Stage 1 and stage 2, N18.1 and N18.2, carry no HCC either.

Can a coder assign N18.31 from a documented eGFR of 50 without the provider stating stage 3a?

No. CKD coding requires provider documentation of the stage. The coder cannot independently derive and assign a stage code from laboratory values. A CDI query is appropriate when the eGFR supports a higher stage than the provider has documented.

Should N18.9 be reported alongside E11.22?

The tabular does not call for it. The Use additional note at E11.22 asks for the stage of chronic kidney disease and names N18.1–N18.6. N18.9 falls outside that range. When an N18 code is reported with E11.22, the Code first note at category N18 sequences E11.22 first.

How is N18.9 sequenced when the patient also has hypertension?

Category N18 carries a Code First instruction for hypertensive chronic kidney disease. Sequence the combination code from the I12.- or I13.- categories first and report N18.9 as an additional code. A causal relationship between hypertension and CKD is assumed unless the provider documents the two as unrelated.

Does N18.9 affect the DRG on an inpatient claim?

N18.9 does not affect the DRG as a secondary diagnosis. N18.9 is on neither the CC list nor the MCC list. Under the FY2027 MS-DRG v44 lists, CMS Tables 6I and 6J, N18.4 and N18.5 are CCs and N18.6 is an MCC.

What changed for N18.9 in FY2027?

N18.9 is unchanged in the FY2027 update, effective 1 October 2026. It was valid in the FY2026 code set. The FY2027 codes and tabular addenda add, delete or revise no code or note in category N18.

What should a reviewer check on an N18.9 claim?

A reviewer should check four points. Whether an eGFR value or other documentation in the record supports a specific stage. Whether N18.9 was added alongside E11.22 while the stage is unknown, which the Use additional note at E11.22 does not call for. Whether a hypertensive combination code from category I12 or I13 was sequenced first. Whether the stage, where one is coded, was authored by the provider rather than derived by the coder.

Related codes

Codes in the same family as N18.9. Only codes with a published page render as links.

Sibling codes in the N18 family

N18.1: Chronic kidney disease, stage 1.
N18.2: Chronic kidney disease, stage 2 (mild).
N18.30: Chronic kidney disease, stage 3 unspecified.
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.

Additional codes to consider

Codes outside the N18 family considered alongside N18.9.

Companion: code alongside when documented

I12-: Hypertensive chronic kidney disease, sequenced first when hypertension and CKD coexist.
I13-: Hypertensive heart and chronic kidney disease, sequenced first when both conditions coexist.
E11.22: Type 2 diabetes mellitus with diabetic chronic kidney disease, with a stage code added when the stage is documented.
Z99.2: Dependence on renal dialysis, coded with N18.6.

Consider instead

N18.30: Chronic kidney disease, stage 3 unspecified, where the note states stage 3 without a 3a or 3b qualifier.
N18.31: Chronic kidney disease, stage 3a, where the provider documents stage 3a.
N18.32: Chronic kidney disease, stage 3b, where the provider documents stage 3b.
N18.4: Chronic kidney disease, stage 4 (severe), where the provider documents stage 4.
N18.5: Chronic kidney disease, stage 5, where the provider documents stage 5 without dialysis dependence.
N18.6: End stage renal disease, where the patient is dialysis dependent.

Sources

All claims on this page derive from government and professional-standards sources.

National Center for Health Statistics. (2026). International classification of diseases, tenth revision, clinical modification (ICD-10-CM) FY2027 files. https://www.cdc.gov/nchs/icd/icd-10-cm/files.html
Centers for Medicare & Medicaid Services and National Center for Health Statistics. (2026). ICD-10-CM official guidelines for coding and reporting FY2027. https://ftp.cdc.gov/pub/Health_Statistics/NCHS/Publications/ICD10CM/2027/ICD-10-CM-October-1-2026-FY27-Guidelines.pdf
Centers for Medicare & Medicaid Services. (2025). 2026 model software/ICD-10 mappings. https://www.cms.gov/medicare/payment/medicare-advantage-rates-statistics/risk-adjustment/2026-model-software-icd-10-mappings
Centers for Medicare & Medicaid Services. (2026). MS-DRG classifications and software, version 44. https://www.cms.gov/medicare/payment/prospective-payment-systems/acute-inpatient-pps/ms-drg-classifications-and-software