2026 ICD-10-CM Diagnosis Code T40.991SPoisoning by other psychodysleptics [hallucinogens], accidental (unintentional), sequela
T40.991S is a billable ICD-10-CM diagnosis code for poisoning by other psychodysleptics [hallucinogens], accidental (unintentional), 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 Mental and substance use disorders; sequela; and Poisoning/toxic effect/adverse effects/underdosing, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
T40.991S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Accidental mescaline overdose
- Accidental poisoning by hallucinogens
- Accidental poisoning by mescaline
- Accidental poisoning by psilocin
- Accidental poisoning by psilocybin
- Accidental psilocybin overdose
- Mescaline overdose
- Phencyclidine intoxication
- Phencyclidine poisoning
- Poisoning by mescaline
- Poisoning by psilocin
- Poisoning by psilocybin
- Psilocybin overdose
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
Mescaline
hallucinogenic alkaloid isolated from the flowering heads (peyote) of lophophora (formerly anhalonium) williamsii, a mexican cactus used in indian religious rites and as an experimental psychotomimetic. among its cellular effects are agonist actions at some types of serotonin receptors. it has no accepted therapeutic uses although it is legal for religious use by members of the native american church.Phencyclidine
a hallucinogen formerly used as a veterinary anesthetic, and briefly as a general anesthetic for humans. phencyclidine is similar to ketamine in structure and in many of its effects. like ketamine, it can produce a dissociative state. it exerts its pharmacological action through inhibition of nmda receptors (receptors, n-methyl-d-aspartate). as a drug of abuse, it is known as pcp and angel dust.Phencyclidine Abuse
the misuse of phencyclidine with associated psychological symptoms and impairment in social or occupational functioning.Receptors, Phencyclidine
specific sites or molecular structures on cell membranes or in cells with which phencyclidine reacts or to which it binds to elicit the specific response of the cell to phencyclidine. studies have demonstrated the presence of multiple receptor sites for pcp. these are the pcp/sigma site, which binds both pcp and psychotomimetic opiates but not certain antipsychotics, and the pcp site, which selectively binds pcp analogs.Psilocybin
the major of two hallucinogenic components of the sacred teonanacatl mushrooms (see psilocybe), the other component being psilocin.
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.
| Substance | Accidental | Self-harm | Assault | Undetermined | Adverse Effect | Underdosing |
|---|---|---|---|---|---|---|
| Bufotenine | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Diethyltryptamine (DET) | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Hawaiian Woodrose seeds | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Heavenly Blue (morning glory) | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Magic mushroom | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Mescal buttons | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Mescaline | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Morning glory seeds | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Pearly Gates (morning glory seeds) | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Peyote | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Phencyclidine | T40.991 | T40.992 | T40.993 | T40.994 | T40.995 | T40.996 |
| Psilocin | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Psilocybin | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Psilocybine | T40.991 | T40.992 | T40.993 | T40.994 | – | – |
| Yohimbic acid | T40.991 | T40.992 | T40.993 | T40.994 | T40.995 | T40.996 |
Convert T40.991S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T40.991SOverview
Is T40.991S a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report poisoning by other psychodysleptics [hallucinogens], accidental (unintentional), sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T40.991S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the poisoning by other psychodysleptics [hallucinogens], accidental (unintentional) itself has resolved, not the original event.
What MS-DRG does T40.991S group to?
When poisoning by other psychodysleptics [hallucinogens], accidental (unintentional), 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 T40.991S 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 other psychodysleptics [hallucinogens], accidental (unintentional), sequela on inpatient claims.
What is the ICD-9 equivalent of T40.991S?
Under the General Equivalence Mappings, poisoning by other psychodysleptics [hallucinogens], accidental (unintentional), sequela converts to ICD-9-CM 909.0 (late eff drug poisoning) and E929.2 (late eff acc poisoning). 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.
