How many milliliters of blood should be drawn for a blood routine examination

A blood routine examination generally requires the extraction of 2-5 milliliters of blood, and the specific amount of blood collected is related to factors such as the number of testing items and instrument sensitivity. As a basic screening item, blood routine test usually requires collecting 2-3 milliliters of venous blood to complete more than 20 indicator tests. Modern fully automatic blood cell analyzers only require a small amount of sample to complete the measurement of a series of parameters such as red blood cells, white blood cells, platelets, etc. For extended blood routine tests that include special tests such as reticulocyte count and abnormal cell screening, it may be necessary to increase the volume to 3-5 milliliters of blood. The specifications of blood collection tubes generally use 2ml or 3ml standard anticoagulant tubes, and some medical institutions may use 5ml blood collection tubes to reserve re examination samples. The use of vacuum negative pressure technology during blood collection can accurately control the amount of blood collected, with an error usually controlled within 0.5 milliliters. The total amount of blood collected in a single test strictly follows the clinical laboratory operating procedures, and there will be no significant fluctuations due to instrument differences. Before the physical examination, fasting should be maintained for 8-12 hours to avoid vigorous exercise affecting blood cell parameters. After blood collection, press the puncture site for more than 5 minutes and avoid lifting heavy objects on the puncture side arm for 24 hours. If there is local bruising, cold compress treatment can be applied. For individuals with normal blood volume, drawing 5 milliliters of blood will not cause significant discomfort.