Glucose monitors checks the concentration of glucose in the blood, called glycemia. Blood is tested for glycemia content by these monitors. The skin is pierced by a lancet, normally at the finger tips, to take a small amount of blood as sample.
This is then placed on a disposable strip which would later change in color or electrical property depending on the type and result of the test. The visual strip type changes in color as blood reacts with chemicals on the test strip. The resulting change in color varies according to glucose concentration. The electrical device type is measured with an electronic meter. Within a few seconds, the digital meter displays the glucose level. It takes from 5 to 60 seconds to read results, varying from model to model. Alternative sites have been suggested for drawing blood samples but they normally do not compare with the finger tips in reflecting rapidly changing levels of glucose.
Glucose monitors are essential in home blood glucose monitoring (HBGM). Several models have come out in the last thirty years. The first units appeared in the 1970s. They were huge and bulky by today's standards. The first devices used the same visual colorimetric system that is still in use in urine test strips. These would require 30 micro liters (µl) of blood samples, referred to as hanging drop, which are quite large compared to only 0.3 to 10 micro liters for today's units. The sizes of the newer monitors are about the size of the palm of an adult's hand. Some models are even smaller while a few are a little larger. Instead of disposable strips, some models have discs that can be reused.
More and newer monitors now have the capability for data transfer. Readings may be downloaded onto a computer that has corresponding diabetes monitoring software through cables or infrared. Some can even be linked to insulin injection devices and PDAs. All monitors feature clocks and memory to store past results. These functions help a person with diabetes to better manage, keep a record, and watch for patterns and developments.
The accuracy of glucose monitors are at about ±10 to 15%. But more factors should be considered regarding these numbers. Elements that may influence accurate readings include the temperature in the immediate surrounding area, humidity, the person's intake of drugs that will be present in the blood, dirt on the meter, calibration of the monitor or meter, percentage of red blood cells in the blood sample, the strips to be used are either new or already old, and the quality and amount of the blood sample. These factors may compromise an accurate measurement. A good way to check and test for accurateness of the monitors is for the user to check for himself the glucose levels at about the same time that a blood sample has been drawn when visiting a doctor and then make comparisons.
Continuous glucose monitoring (CGM) systems make use of a small sensor that is inserted under the skin. They measure levels of glucose in tissue fluid. The individual must wear the sensor in the same place for up to a week. Then it should be replaced. The sensor, after measuring glucose levels, transmits this information to a wireless monitor that may be carried around or worn. However, CGM models are not as accurate and reliable as standard units. They are also much more expensive. In exchange for the higher cost is the ability of the individual for a closer and better glucose monitoring and control. CGM devices can take real-time readings at every 5- or even 1-minute intervals. These come with alarm functions that can warn the diabetic of a too low or too high glucose levels. They also have data transfer capabilities for closer tracking and analysis similar to conventional monitors.
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