The Flupentixol by LC/MS/MS test is a laboratory test used to measure the concentration of the flupentixol drug in the blood. This test is performed to monitor the drug levels and ensure the appropriate therapeutic dose for patients taking this medication to treat psychological disorders such as depression and psychosis. The test also helps avoid overdoses that could cause serious side effects and can be used to adjust the dosage according to the patient's needs or to verify adherence to the treatment.