Theragnosis is a patient-management technique that combines diagnosis and treatment. Theragnosis integrates the domains of tumor diagnosis and therapy in oncology in order to improve upon existing procedures. The prospects for diagnosing disease, directing treatment, and monitoring outcomes bring up a new chapter in precision medicine. To develop efficient new targeted therapies with adequate benefit/risk to patients and a better molecular understanding of how to optimise drug selection, theragnostic encompasses a wide range of subjects, including personalised medicine, pharmacogenomics, and molecular imaging. The imaging agents and medications must be administered efficiently for successful theragnosis applications, resulting in appropriate imaging signal or drug concentration in the targeted disease location.