2026 ICD-10-CM Diagnosis Code T44.0X6AUnderdosing of anticholinesterase agents, initial encounter
T44.0X6A is a billable ICD-10-CM diagnosis code for underdosing of anticholinesterase agents, 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
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T44.0X6A.
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 drugs primarily affecting the autonomic nervous system (T44). 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.
Clinical InformationClinical
Edrophonium
a rapid-onset, short-acting cholinesterase inhibitor used in cardiac arrhythmias and in the diagnosis of myasthenia gravis. it has also been used as an antidote to curare principles.Galantamine
a benzazepine derived from norbelladine. it is found in galanthus and other amaryllidaceae. it is a cholinesterase inhibitor that has been used to reverse the muscular effects of gallamine triethiodide and tubocurarine and has been studied as a treatment for alzheimer disease and other central nervous system disorders.Isoflurophate
a di-isopropyl-fluorophosphate which is an irreversible cholinesterase inhibitor used to investigate the nervous system.Pyridostigmine Bromide
a cholinesterase inhibitor with a slightly longer duration of action than neostigmine. it is used in the treatment of myasthenia gravis and to reverse the actions of muscle relaxants.Tacrine
a cholinesterase inhibitor that crosses the blood-brain barrier. tacrine has been used to counter the effects of muscle relaxants, as a respiratory stimulant, and in the treatment of alzheimer's disease and other central nervous system disorders.
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.
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 T44.0X6A to ICD-9-CMHistory
Code HistoryHistory
Questions About T44.0X6AOverview
Is T44.0X6A (Underdosing of anticholinesterase agents) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of anticholinesterase agents, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T44.0X6A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of anticholinesterase agents, such as an emergency visit or first evaluation.
Can T44.0X6A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of anticholinesterase agents, 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.
