2026 ICD-10-CM Diagnosis Code T46.5X6AUnderdosing of other antihypertensive drugs, initial encounter
T46.5X6A is a billable ICD-10-CM diagnosis code for underdosing of other antihypertensive drugs, 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 T46.5X6A.
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 agents primarily affecting the cardiovascular system (T46). 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
Bethanidine
a guanidinium antihypertensive agent that acts by blocking adrenergic transmission. the precise mode of action is not clear.Clonidine
an imidazoline sympatholytic agent that stimulates alpha-2 adrenergic receptors and central imidazoline receptors. it is commonly used in the management of hypertension.Diazoxide
a benzothiadiazine derivative that is a peripheral vasodilator used for hypertensive emergencies. it lacks diuretic effect, apparently because it lacks a sulfonamide group.Dihydralazine
1,4-dihydrazinophthalazine. an antihypertensive agent with actions and uses similar to those of hydralazine. (from martindale, the extra pharmacopoeia, 30th ed, p354)Dihydroergotamine
a 9,10alpha-dihydro derivative of ergotamine. it is used as a vasoconstrictor, specifically for the therapy of migraine disorders.Ergotamine
a vasoconstrictor found in ergot of central europe. it is a serotonin agonist that has been used as an oxytocic agent and in the treatment of migraine disorders.Ergotamines
a series of structurally-related alkaloids containing the ergotaman backbone structure.Guanabenz
an alpha-2 selective adrenergic agonist used as an antihypertensive agent.Guanethidine
an antihypertensive agent that acts by inhibiting selectively transmission in post-ganglionic adrenergic nerves. it is believed to act mainly by preventing the release of norepinephrine at nerve endings and causes depletion of norepinephrine in peripheral sympathetic nerve terminals as well as in tissues.Guanfacine
a centrally acting antihypertensive agent with specificity towards adrenergic alpha-2 receptors.Hydralazine
a direct-acting vasodilator that is used as an antihypertensive agent.Indapamide
a benzamide-sulfonamide-indole derived diuretic that functions by inhibiting sodium chloride symporters.Carbidopa
an inhibitor of dopa decarboxylase that prevents conversion of levodopa to dopamine. it is used in parkinson disease to reduce peripheral adverse effects of levodopa. it has no anti-parkinson activity by itself.Deoxyepinephrine
sympathomimetic, vasoconstrictor agent.Methyldopa
an alpha-2 adrenergic agonist that has both central and peripheral nervous system effects. its primary clinical use is as an antihypertensive agent.Methysergide
an ergot derivative that is a congener of lysergic acid diethylamide. it antagonizes the effects of serotonin in blood vessels and gastrointestinal smooth muscle, but has few of the properties of other ergot alkaloids. methysergide is used prophylactically in migraine and other vascular headaches and to antagonize serotonin in the carcinoid syndrome.Nitroprusside
a powerful vasodilator used in emergencies to lower blood pressure or to improve cardiac function. it is also an indicator for free sulfhydryl groups in proteins.Pargyline
a monoamine oxidase inhibitor with antihypertensive properties.Pinacidil
a guanidine that opens potassium channels producing direct peripheral vasodilatation of the arterioles. it reduces blood pressure and peripheral resistance and produces fluid retention. (martindale the extra pharmacopoeia, 31st ed)Saralasin
an octapeptide analog of angiotensin ii (bovine) with amino acids 1 and 8 replaced with sarcosine and alanine, respectively. it is a highly specific competitive inhibitor of angiotensin ii that is used in the diagnosis of hypertension.Teprotide
a synthetic nonapeptide (pyr-trp-pro-arg-pro-gln-ile-pro-pro) which is identical to the peptide from the venom of the snake, bothrops jararaca. it inhibits kininase ii and angiotensin i and has been proposed as an antihypertensive agent.Todralazine
an antihypertensive agent with both central and peripheral action; it has some central nervous system depressant effects.Veratrine
a voltage-gated sodium channel activator.
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 T46.5X6A to ICD-9-CMHistory
Code HistoryHistory
Questions About T46.5X6AOverview
Is T46.5X6A (Underdosing of other antihypertensive drugs) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of other antihypertensive drugs, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T46.5X6A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of other antihypertensive drugs, such as an emergency visit or first evaluation.
Can T46.5X6A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of other antihypertensive drugs, 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.
