E21.3 ICD-10-CM Code: Hyperparathyroidism, unspecified
E21.3 is not a CMS-HCC payment code. MEAT criteria · RAF calculator · HCC coding software
HCC Buddy Code Card
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FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Disorders of other endocrine glands (E20-E35)
E21.3
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceHyperparathyroidism, unspecified
Elevated parathyroid hormone and calcium levels when the specific cause or type of hyperparathyroidism has not been determined or documented.
Buddy Insight
Unspecified hyperparathyroidism indicates elevated parathyroid hormone activity without sufficient clinical documentation to categorize it as primary, secondary, or tertiary.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
MappedHCC 23
RAF 0.194
ACA/HHS
MappedHCC 30
Varies by metal level
ESRD/PACE
MappedHCC 23
RAF 0.036
RXHCC
MappedHCC 43
RAF 0.063
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for E21.3 in this effective period.
Excludes 2
Official- familial hypocalciuric hypercalcemia (E83.52)
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for E21.3 in this effective period.
Excludes 1
Official- adult osteomalacia (M83.-)
- ectopic hyperparathyroidism (E34.2)
- hungry bone syndrome (E83.81)
- infantile and juvenile osteomalacia (E55.0)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for E21.3 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for E21.3 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for E21.3 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 E21.3 an HCC code?
Yes. E21.3 maps to Other Significant Endocrine and Metabolic Disorders under the V24 model but is not retained in V28.
- Code
- E21.3
- Description
- Hyperparathyroidism, unspecified
- 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 E21.3 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for E21.3
For E21.3 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 E21.3 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
E21.3 is the ICD-10-CM diagnosis code for hyperparathyroidism, unspecified. Elevated parathyroid hormone and calcium levels when the specific cause or type of hyperparathyroidism has not been determined or documented. E21.3 sits in the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89), within the section covering disorders of other endocrine glands (e20-e35).
Under the older CMS-HCC V24 model, E21.3 maps to Other Significant Endocrine and Metabolic Disorders (HCC 23) with a community, non-dual, aged base RAF weight of 0.194. 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 is a default code used when hyperparathyroidism is diagnosed but insufficient information exists to specify the type. Because E21.3 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 E21.3 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Unspecified hyperparathyroidism indicates elevated parathyroid hormone activity without sufficient clinical documentation to categorize it as primary, secondary, or tertiary. This lack of specificity limits clinical management decisions and should prompt provider query for clarification.
Documentation Requirements
- ✓Attempt to determine whether the hyperparathyroidism is primary, secondary, or tertiary by reviewing lab results, imaging, and clinical history.
- ✓Document parathyroid hormone levels, calcium levels, and any identified underlying etiology.