2026 ICD-10-CM Diagnosis Code T45.7X6AUnderdosing of anticoagulant antagonist, vitamin K and other coagulants, initial encounter
T45.7X6A is a billable ICD-10-CM diagnosis code for underdosing of anticoagulant antagonist, vitamin K and other coagulants, 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). 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 T45.7X6A.
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 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
Ethamsylate
benzenesulfonate derivative used as a systemic hemostatic.Hypoprothrombinemias
absence or reduced levels of prothrombin in the blood.Prothrombin
a plasma protein that is the inactive precursor of thrombin. it is converted to thrombin by a prothrombin activator complex consisting of factor xa, factor v, phospholipid, and calcium ions. deficiency of prothrombin leads to hypoprothrombinemia.Prothrombin Time
clotting time of plasma recalcified in the presence of excess tissue thromboplastin. factors measured are fibrinogen; prothrombin; factor v; factor vii; and factor x. it is used for monitoring anticoagulant therapy with coumarins.Thromboplastin
constituent composed of protein and phospholipid that is widely distributed in many tissues. it serves as a cofactor with factor viia to activate factor x in the extrinsic pathway of blood coagulation.Anticoagulants
agents that prevent blood clotting.Antithrombins
endogenous factors and drugs that directly inhibit the action of thrombin, usually by blocking its enzymatic activity. they are distinguished from indirect thrombin inhibitors, such as heparin, which act by enhancing the inhibitory effects of antithrombins.Carboxypeptidase B2
a carboxypeptidase that removes c-terminal lysine or arginine from peptides and proteins. carboxypeptidase b2 (cpb2) is released into the circulation as a proenzyme which is activated by the thrombin-thrombomodulin complex. activated cpb2 is involved in modulating a variety of processes by cleaving and inactivating various circulating proteins and peptides that are its substrates including fibrin; kinins; and anaphylatoxins.Factor VIIIa
activated form of factor viii. the b-domain of factor viii is proteolytically cleaved by thrombin to form factor viiia. factor viiia exists as a non-covalent dimer in a metal-linked (probably calcium) complex and functions as a cofactor in the enzymatic activation of factor x by factor ixa. factor viiia is similar in structure and generation to factor va.Receptors, Thrombin
a family of proteinase-activated receptors that are specific for thrombin. they are found primarily on platelets and on endothelial cells. activation of thrombin receptors occurs through the proteolytic action of thrombin, which cleaves the n-terminal peptide from the receptor to reveal a new n-terminal peptide that is a cryptic ligand for the receptor. the receptors signal through heterotrimeric gtp-binding proteins. small synthetic peptides that contain the unmasked n-terminal peptide sequence can also activate the receptor in the absence of proteolytic activity.Thrombin
an enzyme formed from prothrombin that converts fibrinogen to fibrin.Thrombin Time
clotting time of plasma mixed with a thrombin solution. it is a measure of the conversion of fibrinogen to fibrin, which is prolonged by afibrinogenemia, abnormal fibrinogen, or the presence of inhibitory substances, e.g., fibrin-fibrinogen degradation products, or heparin. batroxobin, a thrombin-like enzyme unaffected by the presence of heparin, may be used in place of thrombin.Factor VIII
factor viii of blood coagulation. antihemophilic factor that is part of the factor viii/von willebrand factor complex. factor viii is produced in the liver and acts in the intrinsic pathway of blood coagulation. it serves as a cofactor in factor x activation and this action is markedly enhanced by small amounts of thrombin.Factor XI
stable blood coagulation factor involved in the intrinsic pathway. the activated form xia activates factor ix to ixa. deficiency of factor xi is often called hemophilia c.Partial Thromboplastin Time
the time required for the appearance of fibrin strands following the mixing of plasma with phospholipid platelet substitute (e.g., crude cephalins, soybean phosphatides). it is a test of the intrinsic pathway (factors viii, ix, xi, and xii) and the common pathway (fibrinogen, prothrombin, factors v and x) of blood coagulation. it is used as a screening test and to monitor heparin therapy.
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.
Convert T45.7X6A to ICD-9-CMHistory
Code HistoryHistory
Questions About T45.7X6AOverview
Is T45.7X6A a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report underdosing of anticoagulant antagonist, vitamin K and other coagulants, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T45.7X6A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for underdosing of anticoagulant antagonist, vitamin K and other coagulants, such as an emergency visit or first evaluation.
Can T45.7X6A be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because underdosing of anticoagulant antagonist, vitamin K and other coagulants, initial encounter describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
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.
