Question 1

What is ICD-10 code N12?

Accepted Answer

N12 is the ICD-10-CM diagnosis code for tubulo-interstitial nephritis, not specified as acute or chronic. Inflammation of the kidney's tubules and connective tissue where it is unclear whether the condition is acute or chronic. N12 sits in the ICD-10-CM chapter for diseases of the genitourinary system (n00-n99), within the section covering renal tubulo-interstitial diseases (n10-n16).

N12 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.

This code should be used only when the acute versus chronic status cannot be determined from documentation.

Question 2

Is N12 an HCC code?

Accepted Answer

No. N12 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is N12 billable?

Accepted Answer

Yes. N12 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. N12 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Question 4

What is the V28 vs V24 difference for N12?

Accepted Answer

N12 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards N12 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

Question 5

What should coders know when reporting N12?

Accepted Answer

This code should be used only when the acute versus chronic status cannot be determined from documentation Query the provider to clarify the duration and nature of symptoms for more specific coding

N12

Is N12 an HCC code?

What This Code Means

Coding Tips

Excludes 1 — Do NOT code together

Code Hierarchy

Open N12 in the Interactive Encoder