What is a glucose test strip?

These seemingly insignificant strips of plastic are the mainstay of blood glucose testing. It aids patients in monitoring and controlling their diabetes. Glucose test strip is an important component of glucose meters: blood is placed on the strip and the meter provides a reading. Although not commonly used these days, there are also test strips that don’t require a glucose meter. Using this type of strip, blood is placed on the active part and then wiped off after a few seconds. The reagent will cause the strip to change color and the result will be matched on a color chart provided. These strips are cheaper but are less accurate. 

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How do test strips work?

When test strips were first introduced in the early 1980s, the process was difficult for most people. It was hard to operate and it needed a lot of blood. An enzyme used in the early test strips convert the glucose in the drop of blood into dye; the glucose meter shines a beam of light to the strip and detects how much light was absorbed by the dye. The advent of electrochemistry in the ‘90s made test strips what they are today. Instead of dyes, the glucose is converted into electrical current. The meter measures glucose concentration through these electric currents. At least 0.5 μl to 1 μl of blood is needed per reading. It can detect 0 – 3000 mg/dL or 0-3%. Measurements are just approximations and may vary for every manufacturer. Reapplication of blood on the same strip may be necessary for some test strips to work properly.

The quality of glucose strips is an important factor in glucose testing. Better strips mean better readings. Other factors that may affect glucose reading include:

Instability of enzymes – when enzymes are expose to humidity and extreme temperatures, the activity of the enzyme decreases, and so is its accuracy. Glucose strip manufacturers have tried fixing this problem by administering chemicals to stabilize the enzymes.

Strip circuit issues – test strips contain maze-like wire that connects the part with blood sample to the end part inserted into the meter. Small errors in the circuit, such as varying thickness of metal, may alter the current and provide inaccurate readings.

Other blood components – enzymes may get confused by other sugar components of the blood such as maltose. Makers of test strips often used enzymes that only test for glucose and ignore other sugar types. Active ingredients in certain medications may also affect meter readings.

Manufacturers, together with scientists and engineers, keep trying to design better test strips every year to address these issues and to help the increasing number of people with diabetes. In choosing glucose test strips, remember that the brand and type of strips you need also depends on your monitoring devices. Some test strips only work on certain meters.

How long do glucose test strips last?

Once opened, a box of test strips can last for 3 – 6 months but check the information leaflet provided to be sure. Some glucose meters need to be calibrated (manual coding) every time you start a new box of strips. When a meter is miscoded, it will continue to give inaccurate result until you recalibrate it with a correct code. Your blood glucose level may read too high or too low. You may need to insert a chip into the meter or enter a set of numbers (code) to calibrate. If you don’t want the inconvenience of manually coding meters, check for monitoring systems that uses a ‘no-coding technology’. These meters may also require a specific brand or type of glucose test strips to be used.