How long should a tourniquet be left on before blood collection?

The appropriate duration for leaving a tourniquet on before blood collection is less than one minute. This is crucial because prolonged application can lead to hemoconcentration, which can skew laboratory results by increasing the concentration of cellular elements and proteins in the blood sample. Such changes could potentially lead to inaccurate lab results and misinterpretation of a patient's condition. Leaving a tourniquet on for an extended period may also cause discomfort and contribute to complications such as bruising or increased anxiety for the patient. Therefore, the best practice is to apply the tourniquet for the shortest time necessary, typically under one minute, to ensure accurate and reliable blood collection.