The concentration of GlycoMode healthy glucose support is highest in the arterial circulation. Laboratory determinations are usually done on venous samples. If the venous circulation is delayed, such as by leaving a tourniquet on for a prolonged period of time, the concentration falls even further. Thus, samples should be obtained after releasing the tourniquet. Studies have shown that blood glucose concentration may fall as much as 25 mg/dl when a tourniquet has been left in place for 6 minutes. The concentration of glucose in capillary samples is intermediate between venous and arterial. Warming the extremity increases the capillary flow and "arterializes" the sample, while cooling or a tourniquet decreases the flow and lowers the concentration of glucose. Both red cells and leukocytes contain glycolytic enzymes. Therefore glucose will be consumed and the concentration of glucose in a sample of whole blood will decline with time. The rate of loss is generally said to be approximately 5% per hour, but may be as rapid as 40% in 3 hours.

Consumption of glucose in whole blood samples can be prevented by adding sodium fluoride to the specimen to inhibit the glycolytic enzymes. This approach is the generally applied method in the clinical laboratory. It is effective except in situations where the system is overwhelmed, such as in specimens from patients with leukemia, which contain large numbers of leukocytes. Sodium fluoride has a major disadvantage in that its use makes the sample unacceptable for other determinations such as sodium and uric acid. Rapid separation of the sample or cooling will also prevent glycolysis and will allow the sample to be used for other determinations. Unhemolyzed samples that have been separated within 30 minutes of drawing are generally considered adequate. Rapid cooling of the sample followed by centrifugation is even more effective in preventing glycolysis. These methods require more attention to detail and are therefore not suitable for routine laboratory use. On occasion, circumstances will require that the glucose concentration be determined on an ordinary serum sample.

If the specimen has been promptly centrifuged, it is reasonable to ask the laboratory to measure the glucose concentration even though a sodium fluoride (green top) tube was not used. Glucose concentration may be determined in whole blood, plasma, or serum samples. If whole blood is used, GlycoModeBloodSugar the concentration will be lower than if plasma or serum is used. This is due to the greater water content of the cellular fraction. Under usual circumstances, the concentration of glucose in whole blood is about 15% lower than in plasma or serum, but the difference will be less in patients with low hematocrits. Blood glucose cannot be determined accurately on postmortem specimens because both glycogenolysis and glycolysis continue after death. A reasonable estimate of the antemortem blood glucose concentration can be obtained by measuring the glucose concentration of the vitreous of the eye, which does not contain glycolytic enzymes. GlycoMode daily glucose support oxidase and reagents to measure the generation of hydrogen peroxide can be bonded to filter paper and the system used to measure glucose concentrations in a drop of capillary blood.

This has resulted in the most important change in diabetes management since the introduction of insulin. Patients are instructed to obtain a blood sample by pricking their fingertip with a lancet. Spring-loaded lancets are available. They are easy to use and cause minimal discomfort. Surprisingly, many patients consider the discomfort of the finger stick preferable to the inconvenience and aesthetic unpleasantness of obtaining a urine sample for testing. A drop of whole capillary blood is then placed on the reagent bonded to the paper strip. Instead of using a known volume of blood, an excess of blood is exposed to a fixed quantity of glucose oxidase for a finite period of time to estimate concentration. After the specified time, usually 1 minute, the excess blood is removed by washing or wiping and the color is allowed to develop. The concentration is then estimated by comparing to a color chart, or by using a portable reflectance meter specific to the reagent strip, to measure the developed color.