2026 ICD-10-CM Diagnosis Code T50.906AUnderdosing of unspecified drugs, medicaments and biological substances, initial encounter
T50.906A is a billable ICD-10-CM diagnosis code for underdosing of unspecified drugs, medicaments and biological substances, 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). Coders also document this condition as active ingredient availability decreased due to interaction. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Underdosing of drugs and medicaments, initial encounter.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Active ingredient availability decreased due to interaction
- Medication dose too low
- Medication dose too low based on pharmacogenetic finding
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 diuretics and other and unspecified drugs, medicaments and biological substances (T50). 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
Laminaria
a genus of brown algae in the family laminariaceae. dried pencil-like pieces may be inserted in the cervix where they swell as they absorb moisture, serving as osmotic dilators.Saccharin
flavoring agent and non-nutritive sweetener.1,4-alpha-Glucan Branching Enzyme
in glycogen or amylopectin synthesis, the enzyme that catalyzes the transfer of a segment of a 1,4-alpha-glucan chain to a primary hydroxy group in a similar glucan chain. ec 2.4.1.18.Electrophoresis, Starch Gel
electrophoresis in which a starch gel (a mixture of amylose and amylopectin) is used as the diffusion medium.Hydroxyethyl Starch Derivatives
starches that have been chemically modified so that a percentage of oh groups are substituted with 2-hydroxyethyl ether groups.Starch
any of a group of polysaccharides of the general formula (c6-h10-o5)n, composed of a long-chain polymer of glucose in the form of amylose and amylopectin. it is the chief storage form of energy reserve (carbohydrates) in plants.Starch Phosphorylase
an enzyme of the phosphorylases family that catalyzes the degradation of starch, a mixture of unbranched amylose and branched amylopectin compounds. this phosphorylase from plants is the counterpart of glycogen phosphorylase in animals that catalyzes the reaction of inorganic phosphate on the terminal alpha-1,4-glycosidic bond at the non-reducing end of glucans resulting in the release of glucose-1-phosphate.Starch Synthase
an enzyme that catalyzes the transfer of glucose from adpglucose to glucose-containing polysaccharides in 1,4-alpha-linkages. ec 2.4.1.21.
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 T50.906A to ICD-9-CMHistory
Code HistoryHistory
Questions About T50.906AOverview
Is T50.906A a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of unspecified drugs, medicaments and biological substances, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T50.906A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of unspecified drugs, medicaments and biological substances, such as an emergency visit or first evaluation.
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.
