2027 ICD-10-CM Diagnosis Code T39.016AUnderdosing of aspirin, initial encounter
T39.016A is a billable ICD-10-CM diagnosis code for underdosing of aspirin, 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 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 951. The code is not accepted as a principal diagnosis by the Medicare Code Editor. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Underdosing of drugs and medicaments, initial encounter.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T39.016A.
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 nonopioid analgesics, antipyretics and antirheumatics (T39). 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 2027, published by CMS and the National Center for Health Statistics.
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to T39.016A: its own notes plus those printed at T39, block T36-T50, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- adverse effect of correct substance properly administered
- poisoning by overdose of substance
- poisoning by wrong substance given or taken in error
- underdosing by (inadvertently) (deliberately) taking less substance than prescribed or instructed
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- toxic reaction to local anesthesia in pregnancy (O29.3-)
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
Code First
The underlying condition named in the note is sequenced before this code.
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify any retained foreign body, if applicable (Z18.-)
Notes
General instructions on how these codes are used.
- Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
- The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.
7th Character
Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.
- The appropriate 7th character is to be added to each code from category T39
- Ainitial encounter this code
- Dsubsequent encounter
- Ssequela
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name T39.016A, its category, or a range that includes it.
Excludes1 1
These codes carry an Excludes1 note naming T39.016A: they are not reported together with it, unless the two conditions are unrelated.
Excludes2 3
These codes carry an Excludes2 note naming T39.016A: its condition is not part of those codes, and both may be reported when the patient has both.
- T45.52 Poisoning by, adverse effect of and underdosing of antithrombotic drugspoisoning by, adverse effect of and underdosing of aspirin (T39.01-) names T39.01-, which includes this code
- T45.52 Poisoning by, adverse effect of and underdosing of antithrombotic drugspoisoning by, adverse effect of and underdosing of acetylsalicylic acid (T39.01-) names T39.01-, which includes this code
- T48.5 Poisoning by, adverse effect of and underdosing of other anti-common-cold drugspoisoning by, adverse effect of and underdosing of salicylates (T39.0-) names T39.0-, which includes this code
Code First 1
These codes say to code first a condition named in the note, and T39.016A is one of the conditions named.
Use Additional Code 1
These codes say to use an additional code from the note, and T39.016A is one of the codes named.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Aspirin
the prototypical analgesic used in the treatment of mild to moderate pain. it has anti-inflammatory and antipyretic properties and acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. (from martindale, the extra pharmacopoeia, 30th ed, p5)
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 |
|---|---|---|---|---|---|---|
| Acetylsalicylic acid (salts) | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Acetylsalicylic acid (salts)::enteric coated | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Alka-seltzer | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Aluminium, aluminum::aspirin | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Aluminium, aluminum::bis (acetylsalicylate) | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Aspirin (aluminum) (soluble) | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Bufferin | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Calcium::actylsalicylate | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Calcium::carbaspirin | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Carbaspirin | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Fiorinal | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
| Rhodine | T39.011 | T39.012 | T39.013 | T39.014 | T39.015 | T39.016 |
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.
Convert T39.016A to ICD-9-CMHistory
Code HistoryHistory
Questions About T39.016AOverview
What is the ICD-10 code for underdosing of aspirin, initial encounter?
The ICD-10-CM code for underdosing of aspirin, initial encounter is T39.016A (sometimes written as T39016A). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is T39.016A (Underdosing of aspirin) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of aspirin, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What does the 7th character A in T39.016A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of aspirin, such as an emergency visit or first evaluation.
What MS-DRG does T39.016A group to?
On inpatient claims, underdosing of aspirin, initial encounter maps to MS-DRG 951 (other Factors Influencing Health Status), which carries a relative weight of 0.5574. Higher weights mean higher Medicare reimbursement.
Can T39.016A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of aspirin, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
