D75.821 ICD-10-CM Code: Non-immune heparin-induced thrombocytopenia
HCC Buddy Code Card
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FY 2026 Apr update / Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50-D89) / Other disorders of blood and blood-forming organs (D70-D77)
D75.821
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceNon-immune heparin-induced thrombocytopenia
A non-immune reaction to heparin medication that causes a dangerous drop in platelet count, typically occurring within days of heparin exposure.
Buddy Insight
Non-immune heparin-induced thrombocytopenia (HIT Type I) is a benign, transient, non-immune-mediated drop in platelet count occurring within the first 2 days of heparin exposure.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
MappedHCC 48
RAF 0.192
ACA/HHS
MappedHCC 75
Varies by metal level
ESRD/PACE
MappedHCC 48
RAF 0.063
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Non-immune HIT
- Type 1 heparin-induced thrombocytopenia
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for D75.821 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for D75.821 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for D75.821 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for D75.821 in this effective period.
Use Additional
Official- code, if applicable, for adverse effect of heparin (T45.515-)
Code Also
OfficialICD-10-CM does not list Code Also instructions for D75.821 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is D75.821 an HCC code?
Yes. D75.821 maps to Coagulation Defects and Other Specified Hematological Disorders under the V24 model but is not retained in V28.
- Code
- D75.821
- Description
- Non-immune heparin-induced thrombocytopenia
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF
- —
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
Work D75.821 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for D75.821
For D75.821 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed D75.821 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
D75.821 is the ICD-10-CM diagnosis code for non-immune heparin-induced thrombocytopenia. A non-immune reaction to heparin medication that causes a dangerous drop in platelet count, typically occurring within days of heparin exposure. D75.821 sits in the ICD-10-CM chapter for diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (d50-d89), within the section covering other disorders of blood and blood-forming organs (d70-d77).
Under the older CMS-HCC V24 model, D75.821 maps to Coagulation Defects and Other Specified Hematological Disorders (HCC 48) with a community, non-dual, aged base RAF weight of 0.192. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This code specifically indicates non-immune mechanism; do not use if immune-mediated HIT is documented. Because D75.821 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for D75.821 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code specifically indicates non-immune mechanism; do not use if immune-mediated HIT is documented
- •Document the type of heparin exposure (unfractionated vs. low-molecular-weight) when available
Clinical Significance
Non-immune heparin-induced thrombocytopenia (HIT Type I) is a benign, transient, non-immune-mediated drop in platelet count occurring within the first 2 days of heparin exposure. It is caused by direct heparin-platelet interaction and typically resolves spontaneously without heparin discontinuation. Platelet counts rarely fall below 100,000/mcL and no thrombotic complications occur.
Documentation Requirements
- ✓Document the temporal relationship between heparin initiation and platelet count decline (within 1-2 days), the degree of thrombocytopenia (mild), absence of thrombotic complications, and spontaneous resolution.
- ✓Record that immune-mediated HIT (Type II) was excluded based on timing, severity, and negative HIT antibody testing if performed.
Commonly Confused Codes
- •D75.822 (Immune-mediated heparin-induced thrombocytopenia/HIT Type II): far more serious condition requiring immediate heparin cessation and alternative anticoagulation
- •D69.59 (Other secondary thrombocytopenia): non-HIT drug-induced thrombocytopenia
- •D69.6 (Thrombocytopenia, unspecified): less specific.