2026 ICD-10-CM Diagnosis Code T43.596AUnderdosing of other antipsychotics and neuroleptics, initial encounter
T43.596A is a billable ICD-10-CM diagnosis code for underdosing of other antipsychotics and neuroleptics, 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 T43.596A.
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 psychotropic drugs, not elsewhere classified (T43). 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
Amisulpride
a benzamide derivative that is used as an antipsychotic agent for the treatment of schizophrenia. it is also used as an antidepressive agent.Buspirone
an anxiolytic agent and serotonin receptor agonist belonging to the azaspirodecanedione class of compounds. its structure is unrelated to those of the benzodiazapines, but it has an efficacy comparable to diazepam.Droperidol
a butyrophenone with general properties similar to those of haloperidol. it is used in conjunction with an opioid analgesic such as fentanyl to maintain the patient in a calm state of neuroleptanalgesia with indifference to surroundings but still able to cooperate with the surgeon. it is also used as a premedicant, as an antiemetic, and for the control of agitation in acute psychoses. (from martindale, the extra pharmacopoeia, 29th ed, p593)Fluspirilene
a long-acting injectable antipsychotic agent used for chronic schizophrenia.Hydroxyzine
a histamine h1 receptor antagonist that is effective in the treatment of chronic urticaria, dermatitis, and histamine-mediated pruritus. unlike its major metabolite cetirizine, it does cause drowsiness. it is also effective as an antiemetic, for relief of anxiety and tension, and as a sedative.Loxapine
an antipsychotic agent used in schizophrenia.Meprobamate
a carbamate with hypnotic, sedative, and some muscle relaxant properties, although in therapeutic doses reduction of anxiety rather than a direct effect may be responsible for muscle relaxation. meprobamate has been reported to have anticonvulsant actions against petit mal seizures, but not against grand mal seizures (which may be exacerbated). it is used in the treatment of anxiety disorders, and also for the short-term management of insomnia but has largely been superseded by the benzodiazepines. (from martindale, the extra pharmacopoeia, 30th ed, p603)Molindone
an indole derivative effective in schizophrenia and other psychoses and possibly useful in the treatment of the aggressive type of undersocialized conduct disorder. molindone has much lower affinity for d2 receptors than most antipsychotic agents and has a relatively low affinity for d1 receptors. it has only low to moderate affinity for cholinergic and alpha-adrenergic receptors. some electrophysiologic data from animals indicate that molindone has certain characteristics that resemble those of clozapine. (from ama drug evaluations annual, 1994, p283)Olanzapine
a benzodiazepine derivative that binds serotonin receptors; muscarinic receptors; histamine h1 receptors; adrenergic alpha-1 receptors; and dopamine receptors. it is an antipsychotic agent used in the treatment of schizophrenia; bipolar disorder; and major depressive disorder; it may also reduce nausea and vomiting in patients undergoing chemotherapy.Penfluridol
one of the long-acting antipsychotic agents used for maintenance or long-term therapy of schizophrenia and other psychotic disorders.Pimozide
a diphenylbutylpiperidine that is effective as an antipsychotic agent and as an alternative to haloperidol for the suppression of vocal and motor tics in patients with tourette syndrome. although the precise mechanism of action is unknown, blockade of postsynaptic dopamine receptors has been postulated. (from ama drug evaluations annual, 1994, p403)Raclopride
a substituted benzamide that has antipsychotic properties. it is a dopamine d2 receptor (see receptors, dopamine d2) antagonist.Remoxipride
an antipsychotic agent that is specific for dopamine d2 receptors. it has been shown to be effective in the treatment of schizophrenia.Sulpiride
a dopamine d2-receptor antagonist. it has been used therapeutically as an antidepressant, antipsychotic, and as a digestive aid. (from merck index, 11th ed)Tetrabenazine
a drug formerly used as an antipsychotic and treatment of various movement disorders. tetrabenazine blocks neurotransmitter uptake into adrenergic storage vesicles and has been used as a high affinity label for the vesicle transport system.
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 T43.596A to ICD-9-CMHistory
Code HistoryHistory
Questions About T43.596AOverview
Is T43.596A (Underdosing of other antipsychotics and neuroleptics) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of other antipsychotics and neuroleptics, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T43.596A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of other antipsychotics and neuroleptics, such as an emergency visit or first evaluation.
Can T43.596A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of other antipsychotics and neuroleptics, 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.
