2027 ICD-10-CM Diagnosis Code N05.AUnspecified nephritic syndrome with C3 glomerulonephritis

ICD-10-CM Codes›N00–N99›N00-N08›N05

ICD-10-CM N05.A
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

N05.A is a billable ICD-10-CM diagnosis code for unspecified nephritic syndrome with C3 glomerulonephritis. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 698 through 700. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 131 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Nephritis; nephrosis; renal sclerosis.

N05.A does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model. It still risk-adjusts in the ESRD (V21) category 141 for payment year 2027.

Code Identity

ICD-10-CM Code
N05.A
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified nephritic syndrome with C3 glomerulonephritis
Short Description
Unspecified nephritic syndrome with C3 glomerulonephritis
Same as the full description in the CMS dataset.
Parent Code
N05
Unspecified nephritic syndrome

Code Classification

ChapterN00–N99Diseases of the genitourinary system
SectionN00-N08Glomerular diseases
CategoryN05Unspecified nephritic syndrome
This CodeN05.AUnspecified nephritic syndrome with C3 glomerulonephritis

Medicare Risk Adjustment (HCC)Billing

N05.A does not risk-adjust for Medicare Advantage under the CMS-HCC V28 model, but it maps to payment categories in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
no payment category in the model that pays 100% of MA risk scores
Prior Model (CMS-HCC V24)
Not mapped under V24
this diagnosis newly risk-adjusts under the V28 model
Other CMS Models
ESRD (V21): HCC 141
ESRD V21 weights: 0.000 dialysis, 0.000 functioning graft
Part D (RxHCC)
Not mapped
N05.A does not risk-adjust in the RxHCC prescription drug model

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to N05.A: its own notes plus those printed at N05, block N00-N08, and Chapter 14. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From N05 Unspecified nephritic syndrome applies to 11 codes
  • glomerular disease NOS
  • glomerulonephritis NOS
  • nephritis NOS
  • nephropathy NOS and renal disease NOS with morphological lesion specified in .0-.8

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Unspecified nephritic syndrome with C3 glomerulopathy

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

On N05.A itself
  • Unspecified nephritic syndrome (with C3 glomerulopathy) with dense deposit disease (N05.6)
From N05 Unspecified nephritic syndrome applies to 11 codes
  • nephropathy NOS with no stated morphological lesion (N28.9)
  • renal disease NOS with no stated morphological lesion (N28.9)
  • tubulo-interstitial nephritis NOS (N12)
From Block N00-N08 Glomerular diseases applies to 107 codes
  • hypertensive chronic kidney disease (I12.-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 14 (N00-N99) Diseases of the genitourinary system applies to 838 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From Block N00-N08 Glomerular diseases applies to 107 codes
  • any associated kidney failure (N17-N19).

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name N05.A, its category, or a range that includes it.

Excludes1 6

These codes carry an Excludes1 note naming N05.A: they are not reported together with it, unless the two conditions are unrelated.

  • N05.5 Unspecified nephritic syndrome with diffuse mesangiocapillary glomerulonephritis
    Unspecified nephritic syndrome with C3 glomerulonephritis (N05.A)
  • N05.5 Unspecified nephritic syndrome with diffuse mesangiocapillary glomerulonephritis
    Unspecified nephritic syndrome with C3 glomerulopathy (N05.A)
  • N00 Acute nephritic syndrome
    nephritic syndrome NOS (N05.-) names N05.-, which includes this code
  • N01 Rapidly progressive nephritic syndrome
    nephritic syndrome NOS (N05.-) names N05.-, which includes this code
  • N03 Chronic nephritic syndrome
    nephritic syndrome NOS (N05.-) names N05.-, which includes this code
  • N28.9 Disorder of kidney and ureter, unspecified
    unspecified nephritic syndrome (N05.-) names N05.-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR GEN001
Nephritis; nephrosis; renal sclerosis
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Kidney Diseases

You have two kidneys, each about the size of your fist. They are near the middle of your back, just below the rib cage. Inside each kidney there are about a million tiny structures called nephrons. They filter your blood. They remove wastes and extra water, which become urine. The urine flows through tubes called ureters.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code History & ChangesHistory

Replacement N05.A replaces the following previously assigned code(s):

  • N05.8 - Unsp nephritic syndrome with other morphologic changes
FY 2021AddedAdded to the ICD-10-CM code setEffective October 1, 2020.
FY 2022–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About N05.AOverview

What is the ICD-10 code for unspecified nephritic syndrome with C3 glomerulonephritis?

The ICD-10-CM code for unspecified nephritic syndrome with C3 glomerulonephritis is N05.A (sometimes written as N05A). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is N05.A (Unspecified nephritic syndrome) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified nephritic syndrome with C3 glomerulonephritis on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does N05.A group to?

When unspecified nephritic syndrome with C3 glomerulonephritis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 699, 698, 700, with relative weights from 0.6740 to 1.6400 depending on complications. Higher weights mean higher Medicare reimbursement.

Is N05.A a CC or MCC?

CMS lists N05.A as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 131 closely related codes in its exclusion list.

Can N05.A be reported with N05.6?

Not as a rule. The Excludes1 note on N05.A lists "Unspecified nephritic syndrome (with C3 glomerulopathy) with dense deposit disease (N05.6)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

Does N05.A risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage: N05.A maps to no category in the CMS-HCC V28 model. It still risk-adjusts in the ESRD (V21) category 141 (Nephritis).