In modern medicine, theranostics represents a revolutionary confluence of therapy and diagnostics, enabling customised treatment regimens catered to specific patient profiles. This novel technique seeks to enable early disease identification and personalised treatment plans based on the unique subtype or genetic makeup of the ailment, with the goals of improving patient outcomes, decreasing unfavourable side effects, and increasing therapeutic efficacy. Theranostics improves therapy response rates by targeting specific patient traits to reduce resistance and recurrence rates. Furthermore, this approach allows the real-time tracking of therapeutic responses, enabling medical practitioners to modify therapies in response to patient responses. Theranostics has a significant impact on a number of medical specialities, including cancer, neurology, cardiology, and infectious illnesses, providing accurate and efficient treatment.