2026 ICD-10-CM Diagnosis Code T37.0X6AUnderdosing of sulfonamides, initial encounter
T37.0X6A is a billable ICD-10-CM diagnosis code for underdosing of sulfonamides, 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 T37.0X6A.
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 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
Acedapsone
acetylated sulfone that is slowly metabolized to give long-term, low blood levels of dapsone. it has antimicrobial and antimalarial action, but is mainly used as a depot leprostatic agent.Sulfachlorpyridazine
a sulfonamide antimicrobial used for urinary tract infections and in veterinary medicine.Silver Sulfadiazine
antibacterial used topically in burn therapy.Sulfadiazine
one of the short-acting sulfonamides used in combination with pyrimethamine to treat toxoplasmosis in patients with acquired immunodeficiency syndrome and in newborns with congenital infections.Sulfadimethoxine
a sulfanilamide that is used as an anti-infective agent.Sulfadoxine
a long acting sulfonamide that is used, usually in combination with other drugs, for respiratory, urinary tract, and malarial infections.Sulfaguanidine
a sulfanilamide antimicrobial agent that is used to treat enteric infections.Sulfalene
long-acting plasma-bound sulfonamide used for respiratory and urinary tract infections and also for malaria.Sulfamerazine
a sulfanilamide that is used as an antibacterial agent.Sulfameter
long acting sulfonamide used in leprosy, urinary, and respiratory tract infections.Sulfamethazine
a sulfanilamide anti-infective agent. it has a spectrum of antimicrobial action similar to other sulfonamides.Sulfamethizole
a sulfathiazole antibacterial agent.Sulfamethoxazole
a bacteriostatic antibacterial agent that interferes with folic acid synthesis in susceptible bacteria. its broad spectrum of activity has been limited by the development of resistance. (from martindale, the extra pharmacopoeia, 30th ed, p208)Trimethoprim, Sulfamethoxazole Drug Combination
a drug combination with broad-spectrum antibacterial activity against both gram-positive and gram-negative organisms. it is effective in the treatment of many infections, including pneumocystis pneumonia in aids.Sulfamethoxypyridazine
a sulfanilamide antibacterial agent.Sulfamonomethoxine
long acting sulfonamide antibacterial agent.Sulfamoxole
a sulfanilamide antibacterial agent.Sulfanilamide
a short-acting sulfonamide used as an anti-infective agent. it has lower anti-bacterial activity than sulfamethoxazole.Sulfanilamides
compounds based on 4-aminobenzenesulfonamide. the '-anil-' part of the name refers to aniline.Sulfaphenazole
a sulfonilamide anti-infective agent.Sulfapyridine
antibacterial, potentially toxic, used to treat certain skin diseases.Sulfasalazine
a drug that is used in the management of inflammatory bowel diseases. its activity is generally considered to lie in its metabolic breakdown product, 5-aminosalicylic acid (see mesalamine) released in the colon. (from martindale, the extra pharmacopoeia, 30th ed, p907)Sulfathiazole
a sulfathiazole compound that is used as a short-acting anti-infective agent. it is no longer commonly used systemically due to its toxicity, but may still be applied topically in combination with other drugs for the treatment of vaginal and skin infections, and is still used in veterinary medicine.Sulfathiazoles
sulfanilamides consisting of a 4-aminobenzenesulfonamido group at the 2-position of 1,3-thiazole. they are often used as anti-infective agents.Sulfisomidine
a sulfanilamide antibacterial agent.Sulfisoxazole
a short-acting sulfonamide antibacterial with activity against a wide range of gram- negative and gram-positive organisms.
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 T37.0X6A to ICD-9-CMHistory
Code HistoryHistory
Questions About T37.0X6AOverview
Is T37.0X6A (Underdosing of sulfonamides) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of sulfonamides, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T37.0X6A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of sulfonamides, such as an emergency visit or first evaluation.
Can T37.0X6A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of sulfonamides, 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.
