2026 ICD-10-CM Diagnosis Code T50.2X4SPoisoning by carbonic-anhydrase inhibitors, benzothiadiazides and other diuretics, undetermined, sequela
T50.2X4S is a billable ICD-10-CM diagnosis code for poisoning by carbonic-anhydrase inhibitors, benzothiadiazides and other diuretics, undetermined, sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 922 through 923. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Poisoning/toxic effect/adverse effects/underdosing, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
T50.2X4S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
Coding GuidelinesGuidance
When coding a poisoning or reaction to the improper use of a medication (e.g., overdose, wrong substance given or taken in error, wrong route of administration), first assign the appropriate code from categories T36-T50. The poisoning codes have an associated intent as their 5th or 6th character (accidental, intentional self-harm, assault and undetermined). If the intent of the poisoning is unknown or unspecified, code the intent as accidental intent. The undetermined intent is only for use if the documentation in the record specifies that the intent cannot be determined. Use additional code(s) for all manifestations of poisonings.
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
Acetazolamide
one of the carbonic anhydrase inhibitors that is sometimes effective against absence seizures. it is sometimes useful also as an adjunct in the treatment of tonic-clonic, myoclonic, and atonic seizures, particularly in women whose seizures occur or are exacerbated at specific times in the menstrual cycle. however, its usefulness is transient often because of rapid development of tolerance. its antiepileptic effect may be due to its inhibitory effect on brain carbonic anhydrase, which leads to an increased transneuronal chloride gradient, increased chloride current, and increased inhibition. (from smith and reynard, textbook of pharmacology, 1991, p337)Amiloride
a pyrazine compound inhibiting sodium reabsorption through sodium channels in renal epithelial cells. this inhibition creates a negative potential in the luminal membranes of principal cells, located in the distal convoluted tubule and collecting duct. negative potential reduces secretion of potassium and hydrogen ions. amiloride is used in conjunction with diuretics to spare potassium loss. (from gilman et al., goodman and gilman's the pharmacological basis of therapeutics, 9th ed, p705)Bendroflumethiazide
a thiazide diuretic with actions and uses similar to those of hydrochlorothiazide. it has been used in the treatment of familial hyperkalemia, hypertension, edema, and urinary tract disorders. (from martindale, the extra pharmacopoeia, 30th ed, p810)Chlormerodrin
a mercurial compound that has been used as a diuretic but is now superseded by more potent and less toxic drugs. the radiolabeled form has been used as a diagnostic and research tool.Chlorothiazide
a thiazide diuretic with actions and uses similar to those of hydrochlorothiazide. (from martindale, the extra pharmacopoeia, 30th ed, p812)Chlorthalidone
a benzenesulfonamide-phthalimidine that tautomerizes to a benzophenones form. it is considered a thiazide-like diuretic.Clopamide
a sulfamoylbenzamide piperidine. it is considered a thiazide-like diuretic.Cyclopenthiazide
thiazide diuretic also used as an antihypertensive agent.Dichlorphenamide
a carbonic anhydrase inhibitor that is used in the treatment of glaucoma.Ethoxzolamide
a carbonic anhydrase inhibitor used as diuretic and in glaucoma. it may cause hypokalemia.Hydrochlorothiazide
a thiazide diuretic often considered the prototypical member of this class. it reduces the reabsorption of electrolytes from the renal tubules. this results in increased excretion of water and electrolytes, including sodium, potassium, chloride, and magnesium. it is used in the treatment of several disorders including edema, hypertension, diabetes insipidus, and hypoparathyroidism.Hydroflumethiazide
a thiazide diuretic with actions and uses similar to those of hydrochlorothiazide. (from martindale, the extra pharmacopoeia, 30th ed, p822)Mefruside
a benzene-sulfonamide-furan. it is used as a diuretic that affects the concentrating ability of the kidney, increases sodium chloride excretion, but may not spare potassium. it inhibits carbonic anhydrases and may increase the blood uric acid level.Mersalyl
a toxic thiol mercury salt formerly used as a diuretic. it inhibits various biochemical functions, especially in mitochondria, and is used to study those functions.Methazolamide
a carbonic anhydrase inhibitor that is used as a diuretic and in the treatment of glaucoma.Methyclothiazide
a thiazide diuretic with properties similar to those of hydrochlorothiazide. (from martindale, the extra pharmacopoeia, 30th ed, p825)Metolazone
a quinazoline-sulfonamide derived diuretic that functions by inhibiting sodium chloride symporters.Polythiazide
a thiazide diuretic with actions and uses similar to those of hydrochlorothiazide. (from martindale, the extra pharmacopoeia, 30th ed, p826)Triamterene
a pteridinetriamine compound that inhibits sodium reabsorption through sodium channels in renal epithelial cells.Trichlormethiazide
a thiazide diuretic with properties similar to those of hydrochlorothiazide. (from martindale, the extra pharmacopoeia, 30th ed, p830)Fosfomycin
an antibiotic produced by streptomyces fradiae.Tromethamine
an organic amine proton acceptor. it is used in the synthesis of surface-active agents and pharmaceuticals; as an emulsifying agent for cosmetic creams and lotions, mineral oil and paraffin wax emulsions, as a biological buffer, and used as an alkalizer. (from merck, 11th ed; martindale, the extra pharmacopoeia, 30th ed, p1424)Xipamide
a sulfamoylbenzamide analog of clopamide. it is diuretic and saluretic with antihypertensive activity. it is bound to plasma proteins, thus has a delayed onset and prolonged action.
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
Poisoning
A poison is any substance that is harmful to your body. You might swallow it, inhale it, inject it, or absorb it through your skin. Any substance can be poisonous if too much is taken. Poisons can include:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T50.2X4S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T50.2X4SOverview
Is T50.2X4S a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by carbonic-anhydrase inhibitors, benzothiadiazides and other diuretics, undetermined, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T50.2X4S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the poisoning by carbonic-anhydrase inhibitors, benzothiadiazides and other diuretics, undetermined itself has resolved, not the original event.
What MS-DRG does T50.2X4S group to?
When poisoning by carbonic-anhydrase inhibitors, benzothiadiazides and other diuretics, undetermined, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T50.2X4S exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for poisoning by carbonic-anhydrase inhibitors, benzothiadiazides and other diuretics, undetermined, sequela on inpatient claims.
What is the ICD-9 equivalent of T50.2X4S?
Under the General Equivalence Mappings, poisoning by carbonic-anhydrase inhibitors, benzothiadiazides and other diuretics, undetermined, sequela converts to ICD-9-CM 909.0 (late eff drug poisoning) and E989 (late eff inj-undet circ). The mapping is approximate, so confirm the match fits the documentation.
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.
