E21.1 ICD-10-CM Code: Secondary hyperparathyroidism, not elsewhere classified
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FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Disorders of other endocrine glands (E20-E35)
E21.1
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceSecondary hyperparathyroidism, not elsewhere classified
Elevated parathyroid hormone levels that develop as a consequence of another disease, most commonly chronic kidney disease, but not specified elsewhere.
Buddy Insight
Secondary hyperparathyroidism develops as a compensatory response to conditions causing hypocalcemia or phosphate retention, most commonly chronic kidney disease.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
MappedHCC 23
RAF 0.230
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 23
RAF 0.0
RXHCC
MappedHCC 43
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for E21.1 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 E21.1 in this effective period.
Excludes 1
Official- secondary hyperparathyroidism of renal origin (N25.81)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for E21.1 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for E21.1 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for E21.1 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is E21.1 an HCC code?
Yes. E21.1 maps to Other Significant Endocrine and Metabolic Disorders under the V24 model but is not retained in V28.
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. 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.
MEAT Criteria for E21.1
For E21.1to 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 E21.1 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
E21.1 is the ICD-10-CM diagnosis code for secondary hyperparathyroidism, not elsewhere classified. Elevated parathyroid hormone levels that develop as a consequence of another disease, most commonly chronic kidney disease, but not specified elsewhere. E21.1 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, E21.1 maps to Other Significant Endocrine and Metabolic Disorders (HCC 23) with a community, non-dual, aged base RAF weight of 0.230. 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.
Always code the underlying condition (such as chronic kidney disease) in addition to this code. Because E21.1 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 E21.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Always code the underlying condition (such as chronic kidney disease) in addition to this code
- •This code is used when secondary hyperparathyroidism is not due to kidney disease or vitamin D deficiency specifically
Clinical Significance
Secondary hyperparathyroidism develops as a compensatory response to conditions causing hypocalcemia or phosphate retention, most commonly chronic kidney disease. The parathyroid glands become overactive to maintain calcium homeostasis, leading to bone disease and vascular calcification over time.
Documentation Requirements
- ✓Document the underlying cause (chronic kidney disease stage, vitamin D deficiency, malabsorption), parathyroid hormone levels, calcium and phosphorus levels, and treatment approach including phosphate binders or vitamin D analogs.
Excludes 1, Do NOT code together
- secondary hyperparathyroidism of renal origin (N25.81)