Glucometer (or glucose meter)

Glucometer is a medical tool that is used for measuring the approximate level of glucose in the blood.

Working principle of glucometer:

i. A glucometer is a device or a medical tool that plays an important role in determining the concentration of glucose in the solution/blood.
ii. They are mostly based upon the electrochemical technology which uses electrochemical test strips to perform the measurement/test.
iii. A little drop of the solution (generally blood solution) that is to be tested is put on a disposable test strip that the glucometer uses to measure the glucose level in the blood.

Glucometer test strips:

i) In each glucometer test strip which are to be used for determining glucose in the blood, contains an enzyme called glucose oxidase. This enzyme then reacts with the glucose in the blood sample and creates an acid called gluconic acid.
ii) The gluconic acid thus formed then reacts with another chemical in the testing strip called ferricyanide. The ferricyanide and the gluconic acid then combines with each other and forms ferrocyanide.
iii) Immediately as the ferrocyanide has been formed, the device glucometer runs an electronic current through the blood sample on the strip.
iv) The current thus produced is capable of reading the ferrocyanide and identifying the amount of glucose present in the blood sample on the testing strip.
v) This number is the only value that is displayed on the screen of the glucometer.

Methods that are used in electrochemical measurement of glucose:

There are two most common methods that are often used in electrochemical measurement of glucose, they are:

Colorimetric methodAmperometric method

1. Colorimetric method

In this method of electrochemical measurement of glucose is generally performed by using a typical sensors such as LEDs or photo sensors that forms the analog interface. These sensors are then followed by a Transimpedance Amplifier (TIA) for the measurement of glucose level in the solution (generally blood solution).

This method uses the colour reflectance principle in order to sense the colour intensity in the reaction layer of the glucometer test strip by the photometry.

The glucometer also generates or shows a numerical value which is actually a measurement of the glucose concentration that is present in the solution (blood solution).

2. Amperometric method

In this method of electrochemical measurement of glucose, the electrochemical test strip of the glucometer which generally contains a capillary is used to draw in the solution placed at one end of the test strip. This test strip also contains an electrode containing enzyme called as Glucose Oxidase.

Glucose undergoes a chemical reaction in the presence of this enzymes and electrons are produced during this chemical reaction. These electrons (i.e., the charge passing through the electrode) thus produced are then measured which is proportional to the concentration of glucose in the solution.

The blood sample or any other solution containing glucose is placed on the glucometer test strip and the reaction of the glucose with the enzyme occurs which results in the production of electrons that flows through. The flow of these electrons corresponds to the flow of current through the electrodes and changes according to the concentration of the glucose in the blood.

This current is then measured using a transimpedance amplifier (current-to-voltage converter) and an analogue-to-digital converter (ADC). The output of the transimpedance amplifier varies the voltage with varying concentration of glucose in the solution containing glucose or blood solution.