2026 ICD-10-CM Diagnosis Code E21.1Secondary hyperparathyroidism, not elsewhere classified
ICD-10-CM Codes›E00–E89›E20-E35›E21
- Billable — Valid for Submission
- Chronic Condition
E21.1 is a billable ICD-10-CM diagnosis code for secondary hyperparathyroidism, not elsewhere classified. 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 hyperparathyroidism due to intestinal malabsorption. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified endocrine disorders.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Hyperparathyroidism due to intestinal malabsorption
- Hyperparathyroidism due to vitamin D deficiency
- Secondary hyperparathyroidism
- Secondary hyperparathyroidism of nonrenal origin
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Type 1 Excludes
- secondary hyperparathyroidism of renal origin N25.81
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
- non-renal - E21.1
- Osteodystrophy - Q78.9
- parathyroid, secondary - E21.1
External Cause of Injuries IndexGuidance
References for this code in the External Cause of Injuries Index.
- Hyperparathyroidism
- secondary (renal)
- non-renal
- Osteodystrophy
- parathyroid, secondary
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Secondary Hyperparathyroidism
overproduction of parathyroid hormone in response to influence external to the parathyroid glands.
Patient EducationClinical
Parathyroid Disorders
Most people have four pea-sized glands, called parathyroid glands, on the thyroid gland in the neck. Though their names are similar, the thyroid and parathyroid glands are completely different. The parathyroid glands make parathyroid hormone (PTH), which helps your body keep the right balance of calcium and phosphorous.
Read the full article at MedlinePlus
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Convert E21.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About E21.1Overview
Is E21.1 (Hyperparathyroidism and other disorders of parathyroid gland) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report secondary hyperparathyroidism, not elsewhere classified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does E21.1 group to?
When secondary hyperparathyroidism, not elsewhere classified 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.
What is the ICD-9 equivalent of E21.1?
Under the General Equivalence Mappings, secondary hyperparathyroidism, not elsewhere classified converts to ICD-9-CM 252.02 (sec hyprprthyrd nonrenal). The mapping is a direct match.
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.
