2026 ICD-10-CM Diagnosis Code T50.916SUnderdosing of multiple unspecified drugs, medicaments and biological substances, sequela
T50.916S is a billable ICD-10-CM diagnosis code for underdosing of multiple unspecified drugs, medicaments and biological substances, 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Poisoning/toxic effect/adverse effects/underdosing, sequela.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T50.916S.
Present on Admission (POA)Billing
T50.916S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
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 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.
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.
Code History & ChangesHistory
Replacement T50.916S replaces the following previously assigned code(s):
- T50.996S - Underdosing of drug/meds/biol subst, sequela
Questions About T50.916SOverview
Is T50.916S a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of multiple unspecified drugs, medicaments and biological substances, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T50.916S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the underdosing of multiple unspecified drugs, medicaments and biological substances itself has resolved, not the original event.
What MS-DRG does T50.916S group to?
On inpatient claims, underdosing of multiple unspecified drugs, medicaments and biological substances, 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 T50.916S be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of multiple unspecified drugs, medicaments and biological substances, sequela describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
Is T50.916S 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 underdosing of multiple unspecified drugs, medicaments and biological substances, 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.
