2026 ICD-10-CM Diagnosis Code P74.6Transitory hyperammonemia of newborn

ICD-10-CM Codes›P00–P96›P70-P74›P74

ICD-10-CM P74.6
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

P74.6 is a billable ICD-10-CM diagnosis code for transitory hyperammonemia of newborn. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as hyperammonemia. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified perinatal conditions.

Code Identity

ICD-10-CM Code
P74.6
Billable Status
Yes — Valid for Submission
Code Describes
Transitory hyperammonemia of newborn
Short Description
Transitory hyperammonemia of newborn
Same as the full description in the CMS dataset.
Parent Code
P74
Other transitory neonatal electrolyte and metabolic disturbances

Code Classification

ChapterP00–P96Certain conditions originating in the perinatal period
SectionP70-P74Transitory endocrine and metabolic disorders specific to newborn
CategoryP74Other transitory neonatal electrolyte and metabolic disturbances
This CodeP74.6Transitory hyperammonemia of newborn

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Hyperammonemia
  • Transient hyperammonemia in infancy

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.

    • Disturbance(s)
      • electrolyte
        • newborn, transitory
          • hyperammonemia

Clinical ClassificationClinical

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

CCSR PNL013
Other specified and unspecified perinatal conditions
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Carbamoyl-Phosphate Synthase I Deficiency Disease

    a urea cycle disorder manifesting in infancy as lethargy, emesis, seizures, alterations of muscle tone, abnormal eye movements, and an elevation of serum ammonia. the disorder is caused by a reduction in the activity of hepatic mitochondrial carbamoyl-phosphate synthase (ammonia). (menkes, textbook of child neurology, 5th ed, pp50-1)

  • Hyperammonemia

    elevated level of ammonia in the blood. it is a sign of defective catabolism of amino acids or ammonia to urea.

  • Hyperlysinemias

    a group of inherited metabolic disorders which have in common elevations of serum lysine levels. enzyme deficiencies of alpha-aminoadipic semialdehyde dehydrogenase and the saccharopine dehydrogenases have been associated with hyperlysinemia. clinical manifestations include mental retardation, recurrent emesis, hypotonia, lethargy, diarrhea, and developmental delay. (from menkes, textbook of child neurology, 5th ed, p56)

  • Rett Syndrome

    an inherited neurological developmental disorder that is associated with x-linked inheritance and may be lethal in utero to hemizygous males. the affected female is normal until the age of 6-25 months when progressive loss of voluntary control of hand movements and communication skills; ataxia; seizures; autistic behavior; intermittent hyperventilation; and hyperammonemia appear. (from menkes, textbook of child neurology, 5th ed, p199)

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.

Convert P74.6 to ICD-9-CMHistory

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

ICD-9-CM
775.89 Neonat endo/met dis NEC
Approximate The match is approximate rather than exact.

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 P74.6Overview

Is P74.6 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report transitory hyperammonemia of newborn on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What is the ICD-9 equivalent of P74.6?

Under the General Equivalence Mappings, transitory hyperammonemia of newborn converts to ICD-9-CM 775.89 (neonat endo/met dis NEC). The mapping is approximate, so confirm the match fits the documentation.

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.