2026 ICD-10-CM Diagnosis Code T45.515AAdverse effect of anticoagulants, initial encounter
T45.515A is a billable ICD-10-CM diagnosis code for adverse effect of anticoagulants, 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. 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 Adverse effects of drugs and medicaments, initial encounter.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for T45.515A.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Acenocoumarol adverse reaction
- Adverse reaction to coumarin
- Adverse reaction to danaparoid
- Adverse reaction to indanedione
- Anticoagulant adverse reaction
- Coumarin necrosis
- Dalteparin adverse reaction
- Dermatosis caused by coumarin
- Dermatosis resulting from anticoagulant therapy
- Direct acting anticoagulant adverse reaction
- Enoxaparin adverse reaction
- Heparin adverse reaction
- Heparinoid adverse reaction
- Indirect acting anticoagulant adverse reaction
- Pesticide adverse reaction
- Phenindione adverse reaction
- Rectal hemorrhage caused by apixaban
- Rectal hemorrhage caused by drug
- Tinzaparin adverse reaction
- Transfusion reaction caused by toxic effect of anticoagulant
- Warfarin adverse reaction
- Warfarin monitoring status
- Warfarin side effects
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 primarily systemic and hematological agents, not elsewhere classified (T45). 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
Acenocoumarol
a coumarin that is used as an anticoagulant. its actions and uses are similar to those of warfarin. (from martindale, the extra pharmacopoeia, 30th ed, p233)Phenindione
an indandione that has been used as an anticoagulant. phenindione has actions similar to warfarin, but it is now rarely employed because of its higher incidence of severe adverse effects. (from martindale, the extra pharmacopoeia, 30th ed, p234)Phenprocoumon
coumarin derivative that acts as a long acting oral anticoagulant.Warfarin
an anticoagulant that acts by inhibiting the synthesis of vitamin k-dependent coagulation factors. warfarin is indicated for the prophylaxis and/or treatment of venous thrombosis and its extension, pulmonary embolism, and atrial fibrillation with embolization. it is also used as an adjunct in the prophylaxis of systemic embolism after myocardial infarction. warfarin is also used as a rodenticide.
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
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 T45.515A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T45.515AOverview
Is T45.515A (Adverse effect of anticoagulants) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report adverse effect of anticoagulants, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T45.515A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for adverse effect of anticoagulants, such as an emergency visit or first evaluation.
What MS-DRG does T45.515A group to?
On inpatient claims, adverse effect of anticoagulants, initial encounter maps to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.
Can T45.515A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because adverse effect of anticoagulants, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
What is the ICD-9 equivalent of T45.515A?
Under the General Equivalence Mappings, adverse effect of anticoagulants, initial encounter converts to ICD-9-CM 995.29 (adv eff med/biol NEC/NOS) and E934.2 (adv eff anticoagulants). 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.
