2026 ICD-10-CM Diagnosis Code T36.5X6AUnderdosing of aminoglycosides, initial encounter
T36.5X6A is a billable ICD-10-CM diagnosis code for underdosing of aminoglycosides, 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 T36.5X6A.
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 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
Amikacin
a broad-spectrum antibiotic derived from kanamycin. it is reno- and oto-toxic like the other aminoglycoside antibiotics.Kanamycin Kinase
a class of enzymes that inactivate aminocyclitol-aminoglycoside antibiotics (aminoglycosides) by regiospecific phosphorylation of the 3' and/or 5' hydroxyl.Dibekacin
analog of kanamycin with antitubercular as well as broad-spectrum antimicrobial properties.Framycetin
a component of neomycin that is produced by streptomyces fradiae. on hydrolysis it yields neamine and neobiosamine b. (from merck index, 11th ed)Kanamycin
antibiotic complex produced by streptomyces kanamyceticus from japanese soil. comprises 3 components: kanamycin a, the major component, and kanamycins b and c, the minor components.Kanamycin Resistance
nonsusceptibility of bacteria to the antibiotic kanamycin, which can bind to their 70s ribosomes and cause misreading of messenger rna.Netilmicin
semisynthetic 1-n-ethyl derivative of sisomycin, an aminoglycoside antibiotic with action similar to gentamicin, but less ear and kidney toxicity.Novobiocin
an antibiotic compound derived from streptomyces niveus. it has a chemical structure similar to coumarin. novobiocin binds to dna gyrase, and blocks adenosine triphosphatase (atpase) activity. (from reynolds, martindale the extra pharmacopoeia, 30th ed, p189)Paromomycin
an aminoglycoside antibacterial and antiprotozoal agent produced by species of streptomyces.Ribostamycin
a broad-spectrum antimicrobial isolated from streptomyces ribosifidicus.Sisomicin
antibiotic produced by micromonospora inyoensis. it is closely related to gentamicin c1a, one of the components of the gentamicin complex (gentamicins).Spectinomycin
an antibiotic produced by streptomyces spectabilis. it is active against gram-negative bacteria and used for the treatment of gonorrhea.Tobramycin
an aminoglycoside, broad-spectrum antibiotic produced by streptomyces tenebrarius. it is effective against gram-negative bacteria, especially the pseudomonas species. it is a 10% component of the antibiotic complex, nebramycin, produced by the same species.Tobramycin, Dexamethasone Drug Combination
a topical preparation of tobramycin and dexamethasone that is used for treating or preventing superficial bacterial infections of the eye.
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
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 T36.5X6A to ICD-9-CMHistory
Code HistoryHistory
Questions About T36.5X6AOverview
Is T36.5X6A (Underdosing of aminoglycosides) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of aminoglycosides, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T36.5X6A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of aminoglycosides, such as an emergency visit or first evaluation.
Can T36.5X6A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of aminoglycosides, 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.
