Glucose› A substance produced when carbohydrates

from food are broken down in the stomach and intestines during digestion

› Glucose is then absorbed into the blood stream, where insulin (created in the pancreas) facilitates its use by the body’s tissues

A glucose meter (or glucometer) is a medical device for determining the approximate concentration of glucose in the blood.› It is a key element of home blood glucose

monitoring (HBGM) by people with diabetes mellitus or hypoglycemia

› A small drop of blood, obtained by pricking the skin with a lancet, is placed on a disposable test strip that the meter reads and uses to calculate the blood glucose level. The meter then displays the level in mg/dl or mmol/l.

A small drop of blood is placed on a disposable test strip that the meter reads and uses to calculate the blood glucose level. The conductivity of blood is affected by the quantity of glucose present. This biological phenomenon can be modeled with an electrical circuit. The voltage drop in the variable resistance is determined by conductivity of the resistance. When the conductivity is high, the voltage drop is low, and when the conductivity is low, the voltage drop is high. These variations can be analyzed by a microprocessor (MCU) to determine the glucose concentration and display on an LCD.

Steps in Checking a Blood Glucose

Step 1› Body Substance Isolation

Step 2› Prepare Equipment› Place lancet in pen› Place test strip in glucometer

Step 3› Choose site (side of finger)

Step 4› Cleanse site with an alcohol swab in

circular motion › Ensure site is dry prior to poking finger

Step 5› Hold pen tightly against side of finger and

push trigger to release the needle

Step 6› You may need to massage the finger to get

blood flow› Apply test strip to the blood sample› Test strip will absorb blood and will begin to

“count down” Step 7

› Remove test strip from blood sample› Apply direct pressure to puncture site with a

dressing

Step 8› Apply bandage to puncture site

Step 9› Record time and reading on the PCR

Step 10› Remove sharp from glucometer pen, and› place into a sharps container

The functionality of a blood glucose meter can be expanded to allow wired or wireless communication with other devices such as smart phones, insulin dispensers or calorimeters. This can be useful for telehealth applications and remote patient monitoring. Some companies offer specific MCUs with integrated analog blocks and ZigBee® and proprietary wireless solutions for glucometers.

Size: The average size is now approximately the size of the palm of the hand, though some are smaller or larger. They are battery-powered.

Test strips: A consumable element containing chemicals that react with glucose in the drop of blood is used for each measurement. For some models this element is a plastic test strip with a small spot impregnated with glucose oxidase and other components. Each strip is used once and then discarded. Instead of strips, some models use discs that may be used for several readings.

Coding: Since test strips may vary from batch to batch, some models require the user to enter in a code found on the vial of test strips or on a chip that comes with the test strip. By entering the coding or chip into the glucose meter, the meter will be calibrated to that batch of test strips. However, if this process is carried out incorrectly, the meter reading can be up to 4mmol/L inaccuracy. The implications of an incorrectly coded meter can be serious for patients actively managing their diabetes. For miscoded meters, the probability of making an insulin dose error of 2 units is 50%. The probability of making an insulin dose error of 3 units is 24%, compared to 0.49% when using a no coding meter. This may place patients at increased risk of hypoglycaemia.

Volume of blood sample: The size of the drop of blood needed by different models varies from 0.3 to 1 μl. (Older models required larger blood samples, usually defined as a "hanging drop" from the fingertip.) Smaller volume requirements reduce the frequency of unproductive pricks.

Testing times: The times it takes to read a test strip may range from 3 to 60 seconds for different models.

Display: The glucose value in mg/dl or mmol/l is displayed in a small window. The preferred measurement unit varies by country: mg/dl are preferred in the U.S., mmol/l in Canada and Europe. (To convert mmol/l of glucose to mg/dl, multiply by 18. To convert mg/dl of glucose to mmol/l, divide by 18 or multiply by 0.055.) Many machines can toggle between both types of measurements; there have been a couple of published instances in which someone with diabetes has been misled into the wrong action by assuming that a reading in mmol/l was really a very low reading in mg/dl, or the converse.

Glucose vs. plasma glucose: Glucose levels in plasma (one of the components of blood) are generally 10%–15% higher than glucose measurements in whole blood (and even more after eating). This is important because home blood glucose meters measure the glucose in whole blood while most lab tests measure the glucose in plasma. Currently, there are many meters on the market that give results as "plasma equivalent," even though they are measuring whole blood glucose. The plasma equivalent is calculated from the whole blood glucose reading using an equation built into the glucose meter. This allows patients to easily compare their glucose measurements in a lab test and at home. It is important for patients and their health care providers to know whether the meter gives its results as "whole blood equivalent" or "plasma equivalent.“

Clock/memory: All meters now include a clock that is set for date and time, and a memory for past test results. The memory is an important aspect of diabetes care, as it enables the person with diabetes to keep a record of management and look for trends and patterns in blood glucose levels over days. Most memory chips can display an average of recent glucose readings.

Data transfer: Many meters now have more sophisticated data handling capabilities. Many can be downloaded by a cable or infrared to a computer that has diabetes management software to display the test results. Some meters allow entry of additional data throughout the day, such as insulin dose, amounts of carbohydrates eaten, or exercise. A number of meters have been combined with other devices, such as insulin injection devices, PDAs, and even Game Boys.[1] A radio link to an insulin pump allows automatic transfer of glucose readings to a calculator that assists the wearer in deciding on an appropriate insulin dose.