2026 ICD-10-CM Diagnosis Code T40.605SAdverse effect of unspecified narcotics, sequela
T40.605S is a billable ICD-10-CM diagnosis code for adverse effect of unspecified narcotics, 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 not accepted as a principal diagnosis by the Medicare Code Editor and exempt from POA reporting. Coders also document this condition as narcotic embryopathy. 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
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T40.605S.
Present on Admission (POA)Billing
T40.605S 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.
- Narcotic embryopathy
Coding GuidelinesGuidance
When coding an adverse effect of a drug that has been correctly prescribed and properly administered, assign the appropriate code for the nature of the adverse effect followed by the appropriate code for the adverse effect of the drug.
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.
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 |
|---|---|---|---|---|---|---|
| Narcotic (drug) | T40.601 | T40.602 | T40.603 | T40.604 | T40.605 | T40.606 |
| Narcotic (drug)::analgesic NEC | T40.601 | T40.602 | T40.603 | T40.604 | T40.605 | T40.606 |
| Narcotic (drug)::antagonist | T40.601 | T40.602 | T40.603 | T40.604 | T40.605 | T40.606 |
| Narcotic (drug)::specified NEC | T40.601 | T40.602 | T40.603 | T40.604 | T40.605 | T40.606 |
| Narcotic (drug)::synthetic | T40.601 | T40.602 | T40.603 | T40.604 | T40.605 | T40.606 |
| Opiate NEC | T40.601 | T40.602 | T40.603 | T40.604 | T40.605 | T40.606 |
| Opiate NEC::antagonists | T40.601 | T40.602 | T40.603 | T40.604 | T40.605 | T40.606 |
Patient EducationClinical
Drug Reactions
Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions, such as drug interactions, side effects, and allergies.
The full article covers:
- What is a drug interaction?
- What are side effects?
- What are drug allergies?
- How can I stay safe when taking medicines?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T40.605S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T40.605SOverview
Is T40.605S (Adverse effect of unspecified narcotics) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of unspecified narcotics, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T40.605S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the adverse effect of unspecified narcotics itself has resolved, not the original event.
What MS-DRG does T40.605S group to?
On inpatient claims, adverse effect of unspecified narcotics, sequela maps to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T40.605S be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of unspecified narcotics, sequela describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
Is T40.605S 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 adverse effect of unspecified narcotics, sequela on inpatient claims.
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.
