2026 ICD-10-CM Diagnosis Code T38.996AUnderdosing of other hormone antagonists, initial encounter
T38.996A is a billable ICD-10-CM diagnosis code for underdosing of other hormone antagonists, 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 T38.996A.
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 hormones and their synthetic substitutes and antagonists, not elsewhere classified (T38). 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
Octreotide
a potent, long-acting synthetic somatostatin octapeptide analog that inhibits secretion of growth hormone and is used to treat hormone-secreting tumors; diabetes mellitus; hypotension, orthostatic; hyperinsulinism; hypergastrinemia; and small bowel fistula.Receptors, Somatostatin
cell surface proteins that bind somatostatin and trigger intracellular changes which influence the behavior of cells. somatostatin is a hypothalamic hormone, a pancreatic hormone, and a central and peripheral neurotransmitter. activated somatostatin receptors on pituitary cells inhibit the release of growth hormone; those on endocrine and gastrointestinal cells regulate the absorption and utilization of nutrients; and those on neurons mediate somatostatin's role as a neurotransmitter.Somatostatin
a 14-amino acid peptide named for its ability to inhibit pituitary growth hormone release, also called somatotropin release-inhibiting factor. it is expressed in the central and peripheral nervous systems, the gut, and other organs. srif can also inhibit the release of thyroid-stimulating hormone; prolactin; insulin; and glucagon besides acting as a neurotransmitter and neuromodulator. in a number of species including humans, there is an additional form of somatostatin, srif-28 with a 14-amino acid extension at the n-terminal.Somatostatin-28
a 28-amino acid peptide with the same biological activities of somatostatin-14 but with a 14-amino acid extension at the n-terminal. srif-28 is the major form of somatostatin in the gastrointestinal tract.Somatostatinoma
a somatostatin-secreting tumor derived from the pancreatic delta cells (somatostatin-secreting cells). it is also found in the intestine. somatostatinomas are associated with diabetes mellitus; cholelithiasis; steatorrhea; and hypochlorhydria. the majority of somatostatinomas have the potential for metastasis.Somatostatin-Secreting Cells
endocrine cells found throughout the gastrointestinal tract and in islets of the pancreas. d cells secrete somatostatin that acts in both an endocrine and paracrine manner. somatostatin acts on a variety of tissues including the pituitary gland; gastrointestinal tract; pancreas; and kidney by inhibiting the release of hormones, such as growth hormone; gastrin; insulin; and renin.
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
Hormones
Hormones are your body's chemical messengers. They travel in your bloodstream to tissues or organs. They work slowly, over time, and affect many different processes, including:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T38.996A to ICD-9-CMHistory
Code HistoryHistory
Questions About T38.996AOverview
Is T38.996A (Underdosing of other hormone antagonists) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of other hormone antagonists, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T38.996A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of other hormone antagonists, such as an emergency visit or first evaluation.
Can T38.996A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of other hormone antagonists, 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.
