2026 ICD-10-CM Diagnosis Code E87.1Hypo-osmolality and hyponatremia

ICD-10-CM Codes›E00–E89›E70-E88›E87

ICD-10-CM E87.1
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

E87.1 is a billable ICD-10-CM diagnosis code for hypo-osmolality and hyponatremia. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 640 through 641. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Fluid and electrolyte disorders.

Code Identity

ICD-10-CM Code
E87.1
Billable Status
Yes — Valid for Submission
Code Describes
Hypo-osmolality and hyponatremia
Short Description
Hypo-osmolality and hyponatremia
Same as the full description in the CMS dataset.
Parent Code
E87
Other disorders of fluid, electrolyte and acid-base balance

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE70-E88Metabolic disorders
CategoryE87Other disorders of fluid, electrolyte and acid-base balance
This CodeE87.1Hypo-osmolality and hyponatremia

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute hyponatremia
  • Central nervous system disorder of water regulation
  • Cerebral hyponatremia
  • Chorea due to hyponatremia
  • Chronic hyponatremia
  • Dilutional hyponatremia
  • Drug-induced hyponatremia
  • Extracellular fluid volume depletion
  • Hyponatremia
  • Hyponatremia with decreased serum osmolality
  • Hyponatremia with excess extracellular fluid volume
  • Hyponatremia with extracellular fluid depletion
  • Hyponatremia with normal extracellular fluid volume
  • Hypo-osmolality and or hyponatremia
  • Hypoosmolarity
  • Hyposmolality
  • Hyposmolality syndrome
  • Hypotonic disorder
  • Inadequate sodium intake
  • Paraneoplastic hyponatremia
  • Pseudohyponatremia
  • Sodium deficiency

Tabular List NotesGuidance

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

Inclusion Terms

  • Sodium Na deficiency

Type 1 Excludes

  • syndrome of inappropriate secretion of antidiuretic hormone E22.2

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.

    • Cramp(s)
      • salt-depletion
    • Deficiency, deficient
      • natrium
    • Deficiency, deficient
      • salt
    • Deficiency, deficient
      • sodium (Na)
    • Depletion
      • salt or sodium
    • Findings, abnormal, inconclusive, without diagnosis
      • sodium (deficiency)
    • Hyponatremia
    • Hypo-osmolality
    • Low
      • salt syndrome
    • Syndrome
      • hyponatremic
    • Syndrome
      • hyposmolality
    • Syndrome
      • salt
        • depletion
    • Syndrome
      • salt
        • low
    • Syndrome
      • sick
        • cell

Clinical ClassificationClinical

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

CCSR END011
Fluid and electrolyte disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Hyponatremia

    deficiency of sodium in the blood; salt depletion. (dorland, 27th ed)

  • Grade 1 Hyponatremia, CTCAE|Grade 1 Hyponatremia

  • Grade 2 Hyponatremia, CTCAE|Grade 2 Hyponatremia

    125 - <130 mmol/l and asymptomatic

  • Grade 3 Hyponatremia, CTCAE|Grade 3 Hyponatremia

    125 - <130 mmol/l symptomatic; 120 - <125 mmol/l regardless of symptoms

  • Grade 1 Hyponatremia, CTCAE|Grade 1 Hyponatremia

  • Grade 2 Hyponatremia, CTCAE|Grade 2 Hyponatremia

    125-129 mmol/l and asymptomatic

  • Grade 3 Hyponatremia, CTCAE|Grade 3 Hyponatremia

    125-129 mmol/l symptomatic; 120-124 mmol/l regardless of symptoms

  • Grade 4 Hyponatremia, CTCAE|Grade 4 Hyponatremia

    <120 mmol/l; life-threatening consequences

  • Grade 5 Hyponatremia, CTCAE|Grade 5 Hyponatremia

    death

  • Hyponatremia

    lower than normal levels of sodium in the circulating blood.

  • Hyponatremia with Hypoosmolality|Hyponatremia with Hypo-osmolality

    abnormally low serum sodium levels in the setting of electrolyte/fluid imbalance. this condition may be the result of excessive intake or retention of water and/or excretion of salt.

  • Hyponatremia, CTCAE|Hyponatremia|Hyponatremia

    a disorder characterized by laboratory test results that indicate a low concentration of sodium in the blood.

Patient EducationClinical

Fluid and Electrolyte Balance

Electrolytes are minerals that have an electric charge when they are dissolved in water or body fluids, including blood. The electric charge can be positive or negative. You have electrolytes in your blood, urine (pee), tissues, and other body fluids.

The full article covers:

  • What are electrolytes?
  • What are the different types of electrolytes in your body?
  • What is an electrolyte imbalance?
  • What are the different types of electrolyte imbalances?
  • How are electrolyte imbalances diagnosed?
  • What are the treatments for electrolyte imbalances?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert E87.1 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
276.1 Hyposmolality
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About E87.1Overview

Is E87.1 (Other disorders of fluid, electrolyte and acid-base balance) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report hypo-osmolality and hyponatremia on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does E87.1 group to?

When hypo-osmolality and hyponatremia is the principal diagnosis on an inpatient stay, it groups to MS-DRG 640, 641, with relative weights from 0.7782 to 1.3356 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of E87.1?

Under the General Equivalence Mappings, hypo-osmolality and hyponatremia converts to ICD-9-CM 276.1 (hyposmolality). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.