2026 ICD-10-CM Diagnosis Code E20.818Other specified hypoparathyroidism due to impaired parathyroid hormone secretion

ICD-10-CM Codes›E00–E89›E20-E35›E20

ICD-10-CM E20.818
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

E20.818 is a billable ICD-10-CM diagnosis code for other specified hypoparathyroidism due to impaired parathyroid hormone secretion. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 643 through 645. Coders also document this condition as familial isolated hypoparathyroidism. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified endocrine disorders.

Code Identity

ICD-10-CM Code
E20.818
Billable Status
Yes — Valid for Submission
Code Describes
Other specified hypoparathyroidism due to impaired parathyroid hormone secretion
Short Description
Oth hypoparathyroidism due to impaired PTH secretion
Parent Code
E20.81
Hypoparathyroidism due to impaired parathyroid hormone secretion

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE20-E35Disorders of other endocrine glands
CategoryE20Hypoparathyroidism
This CodeE20.818Other specified hypoparathyroidism due to impaired parathyroid hormone secretion

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Familial isolated hypoparathyroidism
  • Hereditary isolated hypoparathyroidism due to agenesis of parathyroid gland
  • Hereditary isolated hypoparathyroidism due to impaired parathormone secretion
  • Hypoparathyroidism due to impaired PTH secretion

Tabular List NotesGuidance

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

Inclusion Terms

  • Familial isolated hypoparathyroidism

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Hypoparathyroidism
      • familial
        • isolated
    • Hypoparathyroidism
      • specified NEC
        • due to impaired parathyroid hormone secretion

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR END015
Other specified and unspecified endocrine disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Code History & ChangesHistory

Replacement E20.818 replaces the following previously assigned code(s):

  • E20.8 - Other hypoparathyroidism
FY 2024AddedAdded to the ICD-10-CM code setEffective October 1, 2023.
FY 2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About E20.818Overview

Is E20.818 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other specified hypoparathyroidism due to impaired parathyroid hormone secretion on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does E20.818 group to?

When other specified hypoparathyroidism due to impaired parathyroid hormone secretion is the principal diagnosis on an inpatient stay, it groups to MS-DRG 643, 644, 645, with relative weights from 0.7683 to 1.6461 depending on complications. Higher weights mean higher Medicare reimbursement.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.