E20.818 ICD-10-CM Code: Other specified hypoparathyroidism due to impaired parathyroid hormone secretion
E20.818 is not a CMS-HCC payment code. MEAT criteria · RAF Calculator · free HCC coding tools
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FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Disorders of other endocrine glands (E20-E35)
E20.818
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther specified hypoparathyroidism due to impaired parathyroid hormone secretion
This condition occurs when the parathyroid glands fail to produce adequate parathyroid hormone, leading to low calcium levels in the blood. It is a rare form of hypoparathyroidism caused by impaired hormone secretion rather than other causes.
Buddy Insight
E20.
CMS-HCC V28
N/A—
Not mapped
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 030
Code-level coefficient reference
ESRD/PACE
MappedHCC 23
Code-level coefficient reference
RXHCC
MappedHCC 43
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Familial isolated hypoparathyroidism
Excludes 2
OfficialNo Excludes 2 notes are included in this display for E20.818. Check the code and parent instructions in the Code Book.
Related Codes
Includes
OfficialNo Includes notes are included in this display for E20.818. Check the code and parent instructions in the Code Book.
Excludes 1
Official- transitory endocrine and metabolic disorders specific to newborn (P70-P74)Inherited from E00-E89, E20-E35, E20
- galactorrhea (N64.3)Inherited from E00-E89, E20-E35, E20
- gynecomastia (N62)Inherited from E00-E89, E20-E35, E20
- Di George's syndrome (D82.1)Inherited from E00-E89, E20-E35, E20
- postprocedural hypoparathyroidism (E89.2)Inherited from E00-E89, E20-E35, E20
- tetany NOS (R29.0)Inherited from E00-E89, E20-E35, E20
- transitory neonatal hypoparathyroidism (P71.4)Inherited from E00-E89, E20-E35, E20
Code First
OfficialNo Code First sequencing instructions are included in this display for E20.818. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for E20.818. Check the code and parent instructions in the Code Book.
Code Also
OfficialNo Code Also instructions are included in this display for E20.818. Check the code and parent instructions in the Code Book.
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 E20.818 an HCC code?
E20.818 is not in the CMS-HCC V28 or V24 community payment model. E20.818 has a separate mapping under the CMS-HCC ESRD model (HCC 23 (Other Significant Endocrine and Metabolic Disorders)) and the Part D RxHCC model (HCC 43 (Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders)); the applicable result needs member context. E20.818 also appears in the HHS-HCC commercial risk model (HCC 030 (HHS-HCC 030 adult, RAF varies by metal level)), which is a commercial market model rather than a Medicare Advantage payment mapping.
- Code
- E20.818
- Description
- Other specified hypoparathyroidism due to impaired parathyroid hormone secretion
- HCC (V28)
- No CMS-HCC V28 mapping
- RAF reference coefficient
- —
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work E20.818 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for E20.818
For E20.818, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- 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
Coder workflow notes
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What This Code Means
E20.818 is the ICD-10-CM diagnosis code for other specified hypoparathyroidism due to impaired parathyroid hormone secretion. This condition occurs when the parathyroid glands fail to produce adequate parathyroid hormone, leading to low calcium levels in the blood. It is a rare form of hypoparathyroidism caused by impaired hormone secretion rather than other causes. E20.818 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).
E20.818 has no mapping under the CMS-HCC V28 or V24 community payment models. E20.818 has a separate mapping under the CMS-HCC ESRD model (HCC 23 (Other Significant Endocrine and Metabolic Disorders)) and the Part D RxHCC model (HCC 43 (Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders)); the applicable result needs member context. E20.818 also appears in the HHS-HCC commercial risk model (HCC 030 (HHS-HCC 030 adult, RAF varies by metal level)), which is a commercial market model rather than a Medicare Advantage payment mapping. Do not assign V28 risk adjustment value from this page; verify the applicable model and payment year before using this code for risk adjustment.
Verify the documentation specifies that the hypoparathyroidism is due to impaired parathyroid hormone secretion, as this distinguishes it from other hypoparathyroidism subtypes (such as surgical removal or genetic forms).
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for E20.818 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify the documentation specifies that the hypoparathyroidism is due to impaired parathyroid hormone secretion, as this distinguishes it from other hypoparathyroidism subtypes (such as surgical removal or genetic forms)
- •Ensure the physician has documented this as 'other specified' rather than unspecified, as E20.9 would be used if the specific type cannot be determined
Clinical Significance
E20.818 captures other specified hypoparathyroidism due to impaired parathyroid hormone secretion not classified as idiopathic, autosomal dominant, secondary, or autoimmune. This may include hypoparathyroidism due to infiltrative processes directly affecting the parathyroid glands, mitochondrial disorders, or other rare genetic conditions affecting parathyroid hormone synthesis or secretion.
Documentation Requirements
- ✓Documentation must confirm hypoparathyroidism with impaired secretion, identify the specific cause, and exclude the more common etiologies that have their own codes.
- ✓Laboratory evidence of low parathyroid hormone, hypocalcemia, and the underlying pathology should be documented.