2026 ICD-10-CM Diagnosis Code T41.5X6AUnderdosing of therapeutic gases, initial encounter

ICD-10-CM Codes›S00–T88›T36-T50›T41

ICD-10-CM T41.5X6A
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T41.5X6A is a billable ICD-10-CM diagnosis code for underdosing of therapeutic gases, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is not accepted as a principal diagnosis by the Medicare Code Editor. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Underdosing of drugs and medicaments, initial encounter.

Code Identity

ICD-10-CM Code
T41.5X6A
Billable Status
Yes — Valid for Submission
Code Describes
Underdosing of therapeutic gases, initial encounter
Short Description
Underdosing of therapeutic gases, initial encounter
Same as the full description in the CMS dataset.
Parent Code
T41.5X6
Underdosing of therapeutic gases

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT36-T50Poisoning by, adverse effect of and underdosing of drugs, medicaments and biological substances
CategoryT41Poisoning by, adverse effect of and underdosing of anesthetics and therapeutic gases
This CodeT41.5X6AUnderdosing of therapeutic gases, initial encounter

Code EditsBilling

Medicare Code Editor checks that affect claim validity for T41.5X6A.

Unacceptable principal diagnosis
There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Coding GuidelinesGuidance

Underdosing refers to taking less of a medication than is prescribed by a provider or a manufacturer's instruction. Codes for underdosing should never be assigned as principal or first-listed codes. If a patient has a relapse or exacerbation of the medical condition for which the drug is prescribed because of the reduction in dose, then the medical condition itself should be coded.

The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of anesthetics and therapeutic gases (T41). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

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

CCSR INJ029
Underdosing of drugs and medicaments, initial encounter
Default principal diagnosis: inpatient No · outpatient No

Clinical InformationClinical

  • 3-Hydroxyanthranilate 3,4-Dioxygenase

    an enzyme that catalyzes the conversion of 3-hydroxyanthranilate to 2-amino-3-carboxymuconate semialdehyde. it was formerly characterized as ec 1.13.1.6.

  • Biological Oxygen Demand Analysis

    testing for the amount of biodegradable organic material in a water sample by measuring the quantity of oxygen consumed by biodegradation of those materials over a specific time period.

  • Blood Gas Monitoring, Transcutaneous

    the noninvasive measurement or determination of the partial pressure (tension) of oxygen and/or carbon dioxide locally in the capillaries of a tissue by the application to the skin of a special set of electrodes. these electrodes contain photoelectric sensors capable of picking up the specific wavelengths of radiation emitted by oxygenated versus reduced hemoglobin.

  • Extracorporeal Membrane Oxygenation

    application of a life support system that circulates the blood through an oxygenating system, which may consist of a pump, a membrane oxygenator, and a heat exchanger. examples of its use are to assist victims of smoke inhalation injury; respiratory failure; and cardiac failure.

  • Heme Oxygenase (Decyclizing)

    a mixed function oxidase enzyme which during hemoglobin catabolism catalyzes the degradation of heme to ferrous iron, carbon monoxide and biliverdin in the presence of molecular oxygen and reduced nadph. the enzyme is induced by metals, particularly cobalt.

  • Heme Oxygenase-1

    a ubiquitous stress-responsive enzyme that catalyzes the oxidative cleavage of heme to yield iron; carbon monoxide; and biliverdin.

  • Homogentisate 1,2-Dioxygenase

    a mononuclear fe(ii)-dependent oxygenase, this enzyme catalyzes the conversion of homogentisate to 4-maleylacetoacetate, the third step in the pathway for the catabolism of tyrosine. deficiency in the enzyme causes alkaptonuria, an autosomal recessive disorder, characterized by homogentisic aciduria, ochronosis and arthritis. this enzyme was formerly characterized as ec 1.13.1.5 and ec 1.99.2.5.

  • Hyperbaric Oxygenation

    the therapeutic intermittent administration of oxygen in a chamber at greater than sea-level atmospheric pressures (three atmospheres). it is considered effective treatment for air and gas embolisms, smoke inhalation, acute carbon monoxide poisoning, caisson disease, clostridial gangrene, etc. (from segen, dictionary of modern medicine, 1992). the list of treatment modalities includes stroke.

  • Hypoxia

    sub-optimal oxygen levels in the ambient air of living organisms.

  • Inositol Oxygenase

    a non-heme iron enzyme that catalyzes the conversion of myoinositol to d-glucuronic acid. the reaction is the first committed step in myoinositol catabolic pathway. this enzyme was formerly characterized as ec 1.13.1.11 and 1.99.2.6.

  • Mixed Function Oxygenases

    widely distributed enzymes that carry out oxidation-reduction reactions in which one atom of the oxygen molecule is incorporated into the organic substrate; the other oxygen atom is reduced and combined with hydrogen ions to form water. they are also known as monooxygenases or hydroxylases. these reactions require two substrates as reductants for each of the two oxygen atoms. there are different classes of monooxygenases depending on the type of hydrogen-providing cosubstrate (coenzymes) required in the mixed-function oxidation.

  • Oxygen

    an element with atomic symbol o, atomic number 8, and atomic weight [15.99903; 15.99977]. it is the most abundant element on earth and essential for respiration.

  • Oxygen Compounds

    inorganic compounds that contain oxygen as an integral part of the molecule.

  • Oxygen Consumption

    the rate at which oxygen is used by a tissue; microliters of oxygen stpd used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (stedman, 25th ed, p346)

  • Oxygen Inhalation Therapy

    inhalation of oxygen aimed at restoring toward normal any pathophysiologic alterations of gas exchange in the cardiopulmonary system, as by the use of a respirator, nasal catheter, tent, chamber, or mask. (from dorland, 27th ed & stedman, 25th ed)

  • Oxygen Isotopes

    stable oxygen atoms that have the same atomic number as the element oxygen, but differ in atomic weight. o-17 and 18 are stable oxygen isotopes.

  • Oxygen Radical Absorbance Capacity

    a measure of the ability of a substance, such as a food, to quench oxygen free radicals in vitro.

  • Oxygen Radioisotopes

    unstable isotopes of oxygen that decay or disintegrate emitting radiation. o atoms with atomic weights 13, 14, 15, 19, and 20 are radioactive oxygen isotopes.

  • Oxygen Saturation

    extent to which hemoglobin is saturated with oxygen typically as measured in arterial blood. it can be measured by various methods (e.g., pulse oxymeter, blood gas analysis). a low blood oxygen saturation level indicates a condition called hypoxemia.

  • Oxygenases

    oxidases that specifically introduce dioxygen-derived oxygen atoms into a variety of organic molecules.

  • Oxygenators

    devices which mechanically oxygenate venous blood extracorporeally. they are used in combination with one or more pumps for maintaining circulation during open heart surgery and for assisting the circulation in patients seriously ill with some cardiac and pulmonary disorders. (umdns, 1999)

  • Oxygenators, Membrane

    devices in which blood and oxygen are separated by a semipermeable membrane, generally of teflon or polypropylene, across which gas exchange occurs. the membrane may be arranged as a series of parallel plates or as a number of hollow fibers; in the latter arrangement, the blood may flow inside the fibers, which are surrounded by gas, or the blood may flow outside the fibers and the gas inside the fibers. (dorland, 28th ed)

  • Photosystem II Protein Complex

    a large multisubunit protein complex found in the thylakoid membrane. it uses light energy derived from light-harvesting protein complexes to catalyze the splitting of water into dioxygen and of reducing equivalents of hydrogen.

  • Reactive Oxygen Species

    molecules or ions formed by the incomplete one-electron reduction of oxygen. these reactive oxygen intermediates include singlet oxygen; superoxides; peroxides; hydroxyl radical; and hypochlorous acid. they contribute to the microbicidal activity of phagocytes, regulation of signal transduction and gene expression, and the oxidative damage to nucleic acids; proteins; and lipids.

  • Singlet Oxygen

    an excited state of molecular oxygen generated photochemically or chemically. singlet oxygen reacts with a variety of biological molecules such as nucleic acids; proteins; and lipids; causing oxidative damages.

  • Tryptophan Oxygenase

    a dioxygenase with specificity for the oxidation of the indoleamine ring of tryptophan. it is a liver-specific enzyme that is the first and rate limiting enzyme in the kynurenine pathway of tryptophan catabolism.

Table of Drugs and ChemicalsClinical

Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.

SubstanceAccidentalSelf-harmAssaultUndeter­minedAdverse
Effect		Under­dosing
OxygenT41.5X1T41.5X2T41.5X3T41.5X4T41.5X5T41.5X6

Patient EducationClinical

Medication Errors

Medicines treat infectious diseases, prevent problems from chronic diseases, and ease pain. But medicines can also cause harmful reactions if not used correctly. Errors can happen in the hospital, at the health care provider's office, at the pharmacy, or at home. You can help prevent errors by:

Read the full article at MedlinePlus

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

Convert T41.5X6A to ICD-9-CMHistory

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

ICD-9-CM
No Map There is no ICD-9 equivalent for this code.

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 T41.5X6AOverview

Is T41.5X6A (Underdosing of therapeutic gases) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of therapeutic gases, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in T41.5X6A mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of therapeutic gases, such as an emergency visit or first evaluation.

Can T41.5X6A be a principal diagnosis?

No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of therapeutic gases, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.

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.