2027 ICD-10-CM Diagnosis Code E87.21Acute metabolic acidosis

ICD-10-CM Codes›E00–E89›E70-E88›E87

ICD-10-CM E87.21
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

E87.21 is a billable ICD-10-CM diagnosis code for acute metabolic acidosis. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 640 through 641, 791, 793. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 17 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Fluid and electrolyte disorders.

Code Identity

ICD-10-CM Code
E87.21
Billable Status
Yes — Valid for Submission
Code Describes
Acute metabolic acidosis
Short Description
Acute metabolic acidosis
Same as the full description in the CMS dataset.
Parent Code
E87.2
Acidosis

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE70-E88Metabolic disorders
CategoryE87Other disorders of fluid, electrolyte and acid-base balance
This CodeE87.21Acute metabolic acidosis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute metabolic acidosis
  • Acute metabolic acidosis with increased anion gap

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to E87.21: its own notes plus those printed at E87.2, E87, block E70-E88, and Chapter 4. A note printed at a category, block or chapter applies to every code under it.

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Acute lactic acidosis

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From E87.2 Acidosis applies to 4 codes
  • diabetic acidosis - see categories E08-E10, E11, E13 with ketoacidosis
From E87 Other disorders of fluid, electrolyte and acid-base balance applies to 14 codes
  • diabetes insipidus (E23.2)
  • electrolyte imbalance associated with hyperemesis gravidarum (O21.1)
  • electrolyte imbalance following ectopic or molar pregnancy (O08.5)
  • familial periodic paralysis (G72.3)
  • metabolic acidemia in newborn, unspecified (P19.9)
From Block E70-E88 Metabolic disorders applies to 286 codes
  • androgen insensitivity syndrome (E34.5-)
  • congenital adrenal hyperplasia (E25.0)
  • hemolytic anemias attributable to enzyme disorders (D55.-)
  • Marfan syndrome (Q87.4-)
  • 5-alpha-reductase deficiency (E29.1)
From Chapter 4 (E00-E89) Endocrine, nutritional and metabolic diseases applies to 973 codes
  • transitory endocrine and metabolic disorders specific to newborn (P70-P74)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Block E70-E88 Metabolic disorders applies to 286 codes
  • Ehlers-Danlos syndromes (Q79.6-)

Notes

General instructions on how these codes are used.

From Chapter 4 (E00-E89) Endocrine, nutritional and metabolic diseases applies to 973 codes
  • All neoplasms, whether functionally active or not, are classified in Chapter 2. Appropriate codes in this chapter (i.e. E05.8, E07.0, E16-E31, E34.-) may be used as additional codes to indicate either functional activity by neoplasms and ectopic endocrine tissue or hyperfunction and hypofunction of endocrine glands associated with neoplasms and other conditions classified elsewhere.

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name E87.21, its category, or a range that includes it.

Excludes2 2

These codes carry an Excludes2 note naming E87.21: its condition is not part of those codes, and both may be reported when the patient has both.

  • R79.1 Abnormal coagulation profile
    abnormality of fluid, electrolyte or acid-base balance (E86-E87) names E86-E87, which includes this code
  • Block T80-T88 Complications of surgical and medical care, not elsewhere classified
    disorders of fluid and electrolyte imbalance (E86-E87) names E86-E87, which includes this code

Use Additional Code 2

These codes say to use an additional code from the note, and E87.21 is one of the codes named.

  • E86 Volume depletion
    code(s) for any associated disorders of electrolyte and acid-base balance (E87.-) names E87.-, which includes this code
  • G90.81 Serotonin syndrome
    metabolic acidosis (E87.2-) names E87.2-, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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

  • Acidosis

    a pathologic condition of acid accumulation or depletion of base in the body. the two main types are respiratory acidosis and metabolic acidosis, due to metabolic acid build up.

Patient EducationClinical

Metabolic Disorders

Metabolism is the process your body uses to get or make energy from the food you eat. Food is made up of proteins, carbohydrates, and fats. Chemicals in your digestive system break the food parts down into sugars and acids, your body's fuel.

Read the full article at MedlinePlus

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

Code History & ChangesHistory

Replacement E87.21 replaces the following previously assigned code(s):

  • E87.2 - Acidosis
FY 2023AddedAdded to the ICD-10-CM code setEffective October 1, 2022.
FY 2024–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About E87.21Overview

What is the ICD-10 code for acute metabolic acidosis?

The ICD-10-CM code for acute metabolic acidosis is E87.21 (sometimes written as E8721). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is E87.21 (Acidosis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report acute metabolic acidosis on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does E87.21 group to?

When acute metabolic acidosis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 641, 640, with relative weights from 0.7864 to 4.2192 depending on complications. Higher weights mean higher Medicare reimbursement.

Is E87.21 a CC or MCC?

CMS lists E87.21 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 17 closely related codes in its exclusion list.

Can E87.21 be reported with E11?

Not as a rule. The Excludes1 note at E87.2, which applies to E87.21, lists "diabetic acidosis - see categories E08-E10, E11, E13 with ketoacidosis". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).