2026 ICD-10-CM Diagnosis Code T36.6X4APoisoning by rifampicins, undetermined, initial encounter
T36.6X4A is a billable ICD-10-CM diagnosis code for poisoning by rifampicins, undetermined, 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) and groups to MS-DRG 917 through 918. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, undetermined; External cause codes: poisoning by drug; and Poisoning by drugs, initial encounter.
Code Identity
Code Classification
Coding GuidelinesGuidance
When coding a poisoning or reaction to the improper use of a medication (e.g., overdose, wrong substance given or taken in error, wrong route of administration), first assign the appropriate code from categories T36-T50. The poisoning codes have an associated intent as their 5th or 6th character (accidental, intentional self-harm, assault and undetermined). If the intent of the poisoning is unknown or unspecified, code the intent as accidental intent. The undetermined intent is only for use if the documentation in the record specifies that the intent cannot be determined. Use additional code(s) for all manifestations of poisonings.
The appropriate 7th character is to be added to each code from block Poisoning by, adverse effect of and underdosing of systemic antibiotics (T36). 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
Rifabutin
a broad-spectrum antibiotic that is being used as prophylaxis against disseminated mycobacterium avium complex infection in hiv-positive patients.Rifampin
a semisynthetic antibiotic produced from streptomyces mediterranei. it has a broad antibacterial spectrum, including activity against several forms of mycobacterium. in susceptible organisms it inhibits dna-dependent rna polymerase activity by forming a stable complex with the enzyme. it thus suppresses the initiation of rna synthesis. rifampin is bactericidal, and acts on both intracellular and extracellular organisms. (from gilman et al., goodman and gilman's the pharmacological basis of therapeutics, 9th ed, p1160)Rifaximin
a synthetic rifamycin derivative and anti-bacterial agent that is used for the treatment of gastroenteritis caused by escherichia coli infections. it may also be used in the treatment of hepatic encephalopathy.
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.
| Substance | Accidental | Self-harm | Assault | Undetermined | Adverse Effect | Underdosing |
|---|---|---|---|---|---|---|
| Ansamycin | T36.6X1 | T36.6X2 | T36.6X3 | T36.6X4 | T36.6X5 | T36.6X6 |
| Rifabutin | T36.6X1 | T36.6X2 | T36.6X3 | T36.6X4 | T36.6X5 | T36.6X6 |
| Rifamide | T36.6X1 | T36.6X2 | T36.6X3 | T36.6X4 | T36.6X5 | T36.6X6 |
| Rifampicin | T36.6X1 | T36.6X2 | T36.6X3 | T36.6X4 | T36.6X5 | T36.6X6 |
| Rifampicin::with isoniazid | T36.6X1 | T36.6X2 | T36.6X3 | T36.6X4 | T36.6X5 | T36.6X6 |
| Rifampin | T36.6X1 | T36.6X2 | T36.6X3 | T36.6X4 | T36.6X5 | T36.6X6 |
| Rifamycin | T36.6X1 | T36.6X2 | T36.6X3 | T36.6X4 | T36.6X5 | T36.6X6 |
| Rifaximin | T36.6X1 | T36.6X2 | T36.6X3 | T36.6X4 | T36.6X5 | T36.6X6 |
Patient EducationClinical
Antibiotics
Antibiotics are medicines that fight bacterial infections in people and animals. They work by killing the bacteria or by making it hard for the bacteria to grow and multiply.
The full article covers:
- What are antibiotics?
- What do antibiotics treat?
- Do antibiotics treat viral infections?
- What are the side effects of antibiotics?
- Why is it important to take antibiotics only when they're needed?
- How do I use antibiotics correctly?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T36.6X4A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T36.6X4AOverview
Is T36.6X4A (Poisoning by rifampicins, undetermined) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by rifampicins, undetermined, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T36.6X4A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for poisoning by rifampicins, undetermined, such as an emergency visit or first evaluation.
What MS-DRG does T36.6X4A group to?
When poisoning by rifampicins, undetermined, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of T36.6X4A?
Under the General Equivalence Mappings, poisoning by rifampicins, undetermined, initial encounter converts to ICD-9-CM 960.6 (pois-antimycobac antibio) and E980.4 (undet pois-med agnt NEC). The mapping is approximate, so confirm the match fits the documentation.
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.
