2026 ICD-10-CM Diagnosis Code T50.8X6AUnderdosing of diagnostic agents, initial encounter
T50.8X6A is a billable ICD-10-CM diagnosis code for underdosing of diagnostic agents, 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 T50.8X6A.
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
Acetrizoic Acid
an iodinated radiographic contrast medium used as acetrizoate sodium in hysterosalpingography.Betazole
a histamine h2 agonist used clinically to test gastric secretory function.Ceruletide
a specific decapeptide obtained from the skin of hila caerulea, an australian amphibian. caerulein is similar in action and composition to cholecystokinin. it stimulates gastric, biliary, and pancreatic secretion; and certain smooth muscle. it is used in paralytic ileus and as diagnostic aid in pancreatic malfunction.Cholecystokinin
a peptide, of about 33 amino acids, secreted by the upper intestinal mucosa and also found in the central nervous system. it causes gallbladder contraction, release of pancreatic exocrine (or digestive) enzymes, and affects other gastrointestinal functions. cholecystokinin may be the mediator of satiety.Receptor, Cholecystokinin A
a subtype of cholecystokinin receptor found primarily in the pancreas; stomach; intestine; and gallbladder. it plays a role in regulating digestive functions such as gallbladder contraction, pancreatic enzyme secretion and absorption in the gastrointestinal tract.Receptor, Cholecystokinin B
a subtype of cholecystokinin receptor found primarily in the central nervous system and the gastric mucosa. it may play a role as a neuromodulator of dopaminergic neurotransmission the regulation of gastric acid secretion from gastric parietal cells.Receptors, Cholecystokinin
cell surface proteins that bind cholecystokinin (cck) with high affinity and trigger intracellular changes influencing the behavior of cells. cholecystokinin receptors are activated by gastrin as well as by cck-4; cck-8; and cck-33. activation of these receptors evokes secretion of amylase by pancreatic acinar cells, acid and pepsin by stomach mucosal cells, and contraction of the pylorus and gallbladder. the role of the widespread cck receptors in the central nervous system is not well understood.Sincalide
an octapeptide hormone present in the intestine and brain. when secreted from the gastric mucosa, it stimulates the release of bile from the gallbladder and digestive enzymes from the pancreas.Tetragastrin
l-tryptophyl-l-methionyl-l-aspartyl-l-phenylalaninamide. the c-terminal tetrapeptide of gastrin. it is the smallest peptide fragment of gastrin which has the same physiological and pharmacological activity as gastrin.Coccidioidin
a sterile solution containing the by-products of growth products of coccidioides immitis, injected intracutaneously as a test for coccidioidomycosis.Congo Red
an acid dye used in testing for hydrochloric acid in gastric contents. it is also used histologically to test for amyloidosis.Diatrizoate
a commonly used x-ray contrast medium. as diatrizoate meglumine and as diatrizoate sodium, it is used for gastrointestinal studies, angiography, and urography.Diatrizoate Meglumine
a versatile contrast medium used for diagnostic x-ray radiology.Evans Blue
an azo dye used in blood volume and cardiac output measurement by the dye dilution method. it is very soluble, strongly bound to plasma albumin, and disappears very slowly.Fluorescein
a phthalic indicator dye that appears yellow-green in normal tear film and bright green in a more alkaline medium such as the aqueous humor.Fluorescein Angiography
visualization of a vascular system after intravenous injection of a fluorescein solution. the images may be photographed or televised. it is used especially in studying the retinal and uveal vasculature.Fluorescein-5-isothiocyanate
fluorescent probe capable of being conjugated to tissue and proteins. it is used as a label in fluorescent antibody staining procedures as well as protein- and amino acid-binding techniques.Fluoresceins
a family of spiro(isobenzofuran-1(3h),9'-(9h)xanthen)-3-one derivatives. these are used as dyes, as indicators for various metals, and as fluorescent labels in immunoassays.Histoplasmin
a mitosporic onygenales fungal genus causing histoplasmosis in humans and animals. its single species is histoplasma capsulatum which has two varieties: h. capsulatum var. capsulatum and h. capsulatum var. duboisii. its teleomorph is ajellomyces capsulatus.Indigo Carmine
indolesulfonic acid used as a dye in renal function testing for the detection of nitrates and chlorates, and in the testing of milk.Indocyanine Green
a tricarbocyanine dye that is used diagnostically in liver function tests and to determine blood volume and cardiac output.Inulin
a starch found in the tubers and roots of many plants. since it is hydrolyzable to fructose, it is classified as a fructosan. it has been used in physiologic investigation for determination of the rate of glomerular function.Iodamide
an ionic monomeric contrast medium. (from martindale, the extra pharmacopoeia, 30th ed, p706)Iodipamide
a water-soluble radiographic contrast media for cholecystography and intravenous cholangiography.Iodohippuric Acid
an iodine-containing compound used in pyelography as a radiopaque medium. if labeled with radioiodine, it can be used for studies of renal function.Iodopyracet
an ionic monomeric contrast medium that was formerly used for a variety of diagnostic procedures. (from martindale, the extra pharmacopoeia, 30th ed, p706)Ioglycamic Acid
a radiopaque medium. it is a mixture of its meglumine and sodium salts and is used to visualize the biliary tract.Iohexol
an effective non-ionic, water-soluble contrast agent which is used in myelography, arthrography, nephroangiography, arteriography, and other radiographic procedures. its low systemic toxicity is the combined result of low chemotoxicity and low osmolality.Iopamidol
a non-ionic, water-soluble contrast agent which is used in myelography, arthrography, nephroangiography, arteriography, and other radiological procedures.Iopanoic Acid
radiopaque medium used as diagnostic aid.Ioxaglic Acid
a low-osmolar, ionic contrast medium used in various radiographic procedures.Metrizamide
a solute for density gradient centrifugation offering higher maximum solution density without the problems of increased viscosity. it is also used as a resorbable, non-ionic contrast medium.Metrizoic Acid
a diagnostic radiopaque that usually occurs as the sodium salt.Metyrapone
an inhibitor of the enzyme steroid 11-beta-monooxygenase. it is used as a test of the feedback hypothalamic-pituitary mechanism in the diagnosis of cushing syndrome.Pentagastrin
a synthetic pentapeptide that has effects like gastrin when given parenterally. it stimulates the secretion of gastric acid, pepsin, and intrinsic factor, and has been used as a diagnostic aid.Phenolsulfonphthalein
red dye, ph indicator, and diagnostic aid for determination of renal function. it is used also for studies of the gastrointestinal and other systems.Propyliodone
radiopaque medium usually in oil; used in bronchography.Enteroendocrine Cells
cells found throughout the lining of the gastrointestinal tract that contain and secrete regulatory peptide hormones and/or biogenic amines.Secretin
a peptide hormone of about 27 amino acids from the duodenal mucosa that activates pancreatic secretion and lowers the blood sugar level. (usan and the usp dictionary of drug names, 1994, p597)Tyropanoate
a diagnostic aid as a radiopaque medium in cholecystography.
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 T50.8X6A to ICD-9-CMHistory
Code HistoryHistory
Questions About T50.8X6AOverview
Is T50.8X6A (Underdosing of diagnostic agents) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of diagnostic agents, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T50.8X6A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of diagnostic agents, such as an emergency visit or first evaluation.
Can T50.8X6A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of diagnostic agents, 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.
