 Second, unless the specimen is drawn into a fluoride tube or processed immediately to separate the serum or plasma from the cells, the measurable glucose will be gradually lowered by "in vitro" metabolism of the glucose at a rate of approximately 7 mg/dL/h, or even more in the presence of leukocytosis.The delay that occurs when blood is drawn at a satellite site and transported to a central laboratory hours later for routine processing is a common cause of mildly low glucose levels in general chemistry panels.Children's blood sugar levels are often slightly lower than adults'.