2026 ICD-10-CM Diagnosis Code T39.2X6AUnderdosing of pyrazolone derivatives, initial encounter
T39.2X6A is a billable ICD-10-CM diagnosis code for underdosing of pyrazolone derivatives, 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 T39.2X6A.
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 nonopioid analgesics, antipyretics and antirheumatics (T39). 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
Aminopyrine
a pyrazolone with analgesic, anti-inflammatory, and antipyretic properties but has risk of agranulocytosis. a breath test with 13c-labeled aminopyrine has been used as a non-invasive measure of cytochrome p-450 metabolic activity in liver function tests.Aminopyrine N-Demethylase
a pyrazolone with analgesic, anti-inflammatory, and antipyretic properties but has risk of agranulocytosis. a breath test with 13c-labeled aminopyrine has been used as a non-invasive measure of cytochrome p-450 metabolic activity in liver function tests.Antipyrine
an analgesic and antipyretic that has been given by mouth and as ear drops. antipyrine is often used in testing the effects of other drugs or diseases on drug-metabolizing enzymes in the liver. (from martindale, the extra pharmacopoeia, 30th ed, p29)Dipyrone
a drug that has analgesic, anti-inflammatory, and antipyretic properties. it is the sodium sulfonate of aminopyrine.Feprazone
a pyrazole that has analgesic, anti-inflammatory, and antipyretic properties. it has been used in mild to moderate pain, fever, and inflammation associated with musculoskeletal and joint disorders. (from martindale, the extra pharmacopoeia, 30th ed, p15)Oxyphenbutazone
a non-steroidal anti-inflammatory drug. oxyphenbutazone eyedrops have been used abroad in the management of postoperative ocular inflammation, superficial eye injuries, and episcleritis. (from ama, drug evaluations annual, 1994, p2000) it had been used by mouth in rheumatic disorders such as ankylosing spondylitis, osteoarthritis, and rheumatoid arthritis but such use is no longer considered justified owing to the risk of severe hematological adverse effects. (from martindale, the extra pharmacopoeia, 30th ed, p27)Phenylbutazone
a butyl-diphenyl-pyrazolidinedione that has anti-inflammatory, antipyretic, and analgesic activities. it has been used in ankylosing spondylitis; rheumatoid arthritis; and reactive arthritis.
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 T39.2X6A to ICD-9-CMHistory
Code HistoryHistory
Questions About T39.2X6AOverview
Is T39.2X6A (Underdosing of pyrazolone derivatives) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of pyrazolone derivatives, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T39.2X6A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of pyrazolone derivatives, such as an emergency visit or first evaluation.
Can T39.2X6A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of pyrazolone derivatives, 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.
