2026 ICD-10-CM Diagnosis Code D84.821Immunodeficiency due to drugs

ICD-10-CM Codes›D50–D89›D80-D89›D84

ICD-10-CM D84.821
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

D84.821 is a billable ICD-10-CM diagnosis code for immunodeficiency due to drugs. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 814 through 816. 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 44 closely related codes. Coders also document this condition as drug-induced immunodeficiency. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Immunity disorders.

D84.821 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 47 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 47, ESRD (V21) category 47, ESRD (V24) category 47, and RxHCC Part D (V08) category 99 for payment year 2026.

Code Identity

ICD-10-CM Code
D84.821
Billable Status
Yes — Valid for Submission
Code Describes
Immunodeficiency due to drugs
Short Description
Immunodeficiency due to drugs
Same as the full description in the CMS dataset.
Parent Code
D84.82
Immunodeficiency due to drugs and external causes

Code Classification

ChapterD50–D89Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism
SectionD80-D89Certain disorders involving the immune mechanism
CategoryD84Other immunodeficiencies
This CodeD84.821Immunodeficiency due to drugs

Medicare Risk Adjustment (HCC)Billing

D84.821 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
Dropped in V28 see all codes that no longer risk-adjust
Prior Model (CMS-HCC V24)
HCC 47
V24 retired last contributed to a Medicare Advantage risk score in payment year 2025
Other CMS Models
PACE (CMS-HCC V22): HCC 47 · ESRD (V21): HCC 47 · ESRD (V24): HCC 47
ESRD V21 weights: 0.097 dialysis, 0.549–0.688 functioning graft · ESRD V24 weights: 0.078 dialysis, 0.523–0.803 functioning graft
Part D (RxHCC)
RxHCC 99 — Immune Disorders
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2026 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.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Drug-induced immunodeficiency
  • Immunodeficiency caused by long term therapeutic use of drug
  • Immunodeficiency caused by long term therapeutic use of immunosuppressant

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Immunodeficiency due to (current or past) medication

Use Additional Code

  • code for adverse effect if applicable, to identify adverse effect of drug T36 T50
  • code, if applicable, for associated long term (current) drug therapy drug or medication such as:
  • long term current drug therapy systemic steroids Z79.52
  • other long term current drug therapy Z79.899

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 BLD008
Immunity disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Code History & ChangesHistory

Replacement D84.821 replaces the following previously assigned code(s):

  • D84.8 - Other specified immunodeficiencies
FY 2021AddedAdded to the ICD-10-CM code setEffective October 1, 2020.
FY 2022–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About D84.821Overview

What is the ICD-10 code for immunodeficiency due to drugs?

The ICD-10-CM code for immunodeficiency due to drugs is D84.821 (sometimes written as D84821). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is D84.821 (Immunodeficiency due to drugs and external causes) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report immunodeficiency due to drugs on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does D84.821 group to?

When immunodeficiency due to drugs is the principal diagnosis on an inpatient stay, it groups to MS-DRG 814, 815, 816, with relative weights from 0.6320 to 2.1267 depending on complications. Higher weights mean higher Medicare reimbursement.

Is D84.821 a CC or MCC?

CMS lists D84.821 as a CC (complication or comorbidity) for FY 2026. 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 44 closely related codes in its exclusion list.

Does D84.821 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage. D84.821 mapped to HCC 47 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 47 (Disorders of Immunity), ESRD (V21) category 47 (Disorders of Immunity), ESRD (V24) category 47 (Disorders of Immunity), and RxHCC Part D (V08) category 99 (Immune Disorders).