2026 ICD-10-CM Diagnosis Code T37.3X6AUnderdosing of other antiprotozoal drugs, initial encounter
T37.3X6A is a billable ICD-10-CM diagnosis code for underdosing of other antiprotozoal drugs, 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 T37.3X6A.
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 other systemic anti-infectives and antiparasitics (T37). 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
Emetine
the principal alkaloid of ipecac, from the ground roots of uragoga (or cephaelis) ipecacuanha or u. acuminata, of the rubiaceae. it is used as an amebicide in many different preparations and may cause serious cardiac, hepatic, or renal damage and violent diarrhea and vomiting. emetine inhibits protein synthesis in eukaryotic cells but not prokaryotic cells.Glaucarubin
(1 beta,2 alpha,11 beta,12 alpha,15 beta(s))-11,20-epoxy-1,2,11,12-tetrahydroxy-15-(2-hydroxy-2-methyl-1-oxobutoxy)picras-3-en-16-one. a quassinoid (simaroubolide) from simaruba glauca, a tropical shrub. it has been used as an antiamebic agent and is found to be cytotoxic. it may be of use in cancer chemotherapy.Melarsoprol
arsenical used in trypanosomiases. it may cause fatal encephalopathy and other undesirable side effects.Misonidazole
a nitroimidazole that sensitizes normally radio-resistant hypoxic cells to radiation. it may also be directly cytotoxic to hypoxic cells and has been proposed as an antineoplastic.Nifurtimox
a nitrofuran thiazine that has been used against trypanosomiasis.Nimorazole
an antitrichomonal agent which is effective either topically or orally and whose urinary metabolites are also trichomonicidal.Ornidazole
a nitroimidazole antiprotozoal agent used in ameba and trichomonas infections. it is partially plasma-bound and also has radiation-sensitizing action.Pentamidine
antiprotozoal agent effective in trypanosomiasis, leishmaniasis, and some fungal infections; used in treatment of pneumocystis pneumonia in hiv-infected patients. it may cause diabetes mellitus, central nervous system damage, and other toxic effects.Tinidazole
a nitroimidazole alkylating agent that is used as an antitrichomonal agent against trichomonas vaginalis; entamoeba histolytica; and giardia lamblia infections. it also acts as an antibacterial agent for the treatment of bacterial vaginosis and anaerobic bacterial infections.
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 T37.3X6A to ICD-9-CMHistory
Code HistoryHistory
Questions About T37.3X6AOverview
Is T37.3X6A (Underdosing of other antiprotozoal drugs) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of other antiprotozoal drugs, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T37.3X6A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of other antiprotozoal drugs, such as an emergency visit or first evaluation.
Can T37.3X6A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of other antiprotozoal drugs, 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.
