Diagnosis of inotropic agent toxicity typically involves a combination of clinical assessment and laboratory tests. A thorough medical history and physical examination are essential. Blood levels of the suspected toxic agent, such as serum digoxin levels, can be measured to confirm toxicity. Electrolyte levels should also be checked, as imbalances can exacerbate toxic effects. An ECG is crucial for detecting arrhythmias or other electrical disturbances in the heart.