2026 ICD-10-CM Diagnosis Code T40.2X4APoisoning by other opioids, undetermined, initial encounter
T40.2X4A is a billable ICD-10-CM diagnosis code for poisoning by other opioids, undetermined, 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) and groups to MS-DRG 917 through 918. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, undetermined; External cause codes: poisoning by drug; and Opioid-related disorders.
Code Identity
Code Classification
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 narcotics and psychodysleptics [hallucinogens] (T40). 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
Codeine
an opioid analgesic related to morphine but with less potent analgesic properties and mild sedative effects. it also acts centrally to suppress cough.Dextrorphan
dextro form of levorphanol. it acts as a noncompetitive nmda receptor antagonist, among other effects, and has been proposed as a neuroprotective agent. it is also a metabolite of dextromethorphan.Dihydromorphine
a semisynthetic analgesic used in the study of narcotic receptors.Ethylmorphine
a narcotic analgesic and antitussive. it is metabolized in the liver by ethylmorphine-n-demethylase and used as an indicator of liver function.Ethylmorphine-N-Demethylase
a drug-metabolizing enzyme of the hepatic microsomal oxidase system which catalyzes the oxidation of the n-methyl group of ethylmorphine with the formation of formaldehyde.Etorphine
a narcotic analgesic morphinan used as a sedative in veterinary practice.Hydrocodone
narcotic analgesic related to codeine, but more potent and more addicting by weight. it is used also as cough suppressant.Hydromorphone
an opioid analgesic made from morphine and used mainly as an analgesic. it has a shorter duration of action than morphine.Glucuronosyltransferase
a family of enzymes accepting a wide range of substrates, including phenols, alcohols, amines, and fatty acids. they function as drug-metabolizing enzymes that catalyze the conjugation of udpglucuronic acid to a variety of endogenous and exogenous compounds. ec 2.4.1.17.Morphine
the principal alkaloid in opium and the prototype opiate analgesic and narcotic. morphine has widespread effects in the central nervous system and on smooth muscle.Morphine Dependence
strong dependence, both physiological and emotional, upon morphine.Morphine Derivatives
analogs or derivatives of morphine.Receptors, Opioid, mu
a class of opioid receptors recognized by its pharmacological profile. mu opioid receptors bind, in decreasing order of affinity, endorphins, dynorphins, met-enkephalin, and leu-enkephalin. they have also been shown to be molecular receptors for morphine.Oxycodone
a semisynthetic derivative of codeine.Oxymorphone
an opioid analgesic with actions and uses similar to those of morphine, apart from an absence of cough suppressant activity. it is used in the treatment of moderate to severe pain, including pain in obstetrics. it may also be used as an adjunct to anesthesia. (from martindale, the extra pharmacopoeia, 30th ed, p1092)Promedol
a narcotic analgesic similar to meperidine; it exists in four stereoisomers, two of which, the beta (isopromedol) and the gamma (trimeperidine) are active.Thebaine
a drug that is derived from opium, which contains from 0.3-1.5% thebaine depending on its origin. it produces strychnine-like convulsions rather than narcosis. it may be habit-forming and is a controlled substance (opiate) listed in the u.s. code of federal regulations, title 21 part 1308.12 (1985). (from merck index, 11th ed)
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
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Convert T40.2X4A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T40.2X4AOverview
Is T40.2X4A (Poisoning by other opioids, undetermined) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by other opioids, undetermined, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T40.2X4A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for poisoning by other opioids, undetermined, such as an emergency visit or first evaluation.
What MS-DRG does T40.2X4A group to?
When poisoning by other opioids, undetermined, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of T40.2X4A?
Under the General Equivalence Mappings, poisoning by other opioids, undetermined, initial encounter converts to ICD-9-CM 965.09 (poisoning-opiates NEC) and E980.0 (undeterm pois-analgesics). 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.
