Table of Contents
Key Takeaways
Glucose test strips rely on chemical reactions involving enzymes, and exposure to heat, humidity, and other environmental conditions can affect how they work
Keeping strips in their original closed container helps to protect the strips from moisture in the air
Check both the expiration date and the discard period that applies after opening the container
Control solution testing can help you check that your meter and test strips are working properly
Disclaimer: This article is for informational and educational purposes only and does not constitute medical advice. Always follow the instructions provided with your glucose meter and test strips, and speak with a qualified healthcare professional if your readings repeatedly seem inaccurate, do not match your symptoms, or you are unsure how to respond to a glucose result.
Even though a blood glucose test strip might look simple, there’s a complex chemical reaction that takes place when the glucose in the blood sample comes into contact with the chemicals (or enzyme reagents) in the test strip. That reaction produces a tiny electrical current which your glucose meter converts into a reading. Those chemical components need to work within specific conditions, and test strips are manufactured to remain stable under specific storage conditions, so how test strips are stored and handled can affect the accuracy of your results.
Why Test Strip Storage Affects Your Readings
Exposure to conditions outside of those recommended by the manufacturer can affect the components that are part of the glucose-testing chemical reaction. The enzymes in the test strip are proteins, and proteins are sensitive to their environment. Excessive heat, humidity, and prolonged storage can gradually reduce their activity or stability.1 The importance here is what it means for your glucose readings: a strip with a partially degraded enzyme might still produce a reading, but it could be an incorrect one.2 The FDA notes that improperly stored blood glucose meters and test strips can result in less accurate glucose readings.3 This is why it’s important to store your glucose test strips according to the manufacturer’s instructions.
Several environmental factors can affect test strip accuracy, including altitude, temperature, and humidity.
Altitude
The chemicals in certain glucose strips are sensitive to oxygen concentrations, so the lower oxygen concentration at high altitude can affect the chemical reaction leading to falsely high glucose readings.2
Temperature
The effects of temperature on the strips are less predictable and tend to be brand-specific.2 Temperature can also affect the reaction itself, but because of how complex the chemical reaction is, different glucose strip brands can react differently to the high temperature exposure. Some strips might overestimate the glucose reading while others could underestimate it, so you may get a reading that’s very different because of these improper storage conditions.
Humidity
Humidity can also affect test-strip performance. The enzymes in the test strip are packaged in a dry state, so being exposed to humidity can prematurely rehydrate the proteins which can limit their reactivity during the glucose testing.1 Extreme temperature and humidity can result in significantly different glucose readings compared to strips stored under recommended conditions.4
In practice, keep your test strips within the temperature and humidity range specified by the manufacturer. For example, True Metrix test strips should be stored between 40°F and 86°F, and the manufacturer advises keeping them away from extreme temperatures, high humidity, and direct sunlight.5
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Does It Matter Which Strips You Use?
Blood glucose meters are designed to work with specific test strips, so using ones that aren’t intended for your meter could result in inaccurate readings.6 Always check that the strips you buy are compatible with your meter. For example, if you use a True Metrix meter, True Metrix blood glucose test strips are one option designed for that system. Even if strips look very similar, their chemical makeup and how they interact with the meter might differ.
Expiration Date vs. Discard Date
The manufacturer’s expiration date, which is printed on the test strip box or container, tells you how long the unopened test strips should remain stable if they’re stored correctly. Some test strips also have a separate discard period, which is sometimes written on the package insert rather than on the container itself. This discard period begins when you first open the container, and it’s often shorter than the expiration date.7 The manufacturer may instruct you to discard any remaining strips after a certain period of time after opening the container, even if the expiration date hasn’t passed yet. Writing the date when you open the container on the label makes it easier to keep track of when the discard period ends.
Checking Your Meter With Control Solution
Control solution is a liquid containing a known amount of glucose. So if you use it on the test strip (like you’d do with your usual blood sample), the result should fall within the expected range that’s specified on the control solution or the test-strip labelling.3 This is useful if you’re concerned that your test strips may have been affected by storage conditions, as it can help check whether your meter and test strips are still working properly.
The FDA advises running a control solution check:3
When you open a new container of test strips
If you drop your meter
If a reading doesn’t seem to match how you feel
Periodically while using the container
If the result doesn’t fall within the expected range, the issue might be with the test strips or meter. Check the instructions for your meter and strips, including the storage requirements and expiration or discard dates.
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The TRUE METRIX Glucose Control Solution is for use with the TRUE METRIX Self Monitoring Meter and TRUE METRIX Self Monitoring Test Strips to check that the meter and the test strip are working together properly and the test is… read more
Bottom Line
Glucose test strips rely on a carefully controlled chemical reaction that lets your meter detect the glucose in your blood and record it as a reading. The enzymes and other components involved in this reaction can be affected by heat, humidity, time, and other environmental conditions, so correct test strip storage is important. Keeping them within the manufacturer’s recommended storage conditions and keeping track of expiration and discard dates helps to ensure reliable readings.
References
Tonyushkina K, Nichols JH. Glucose meters: a review of technical challenges to obtaining accurate results. J Diabetes Sci Technol. 2009 Jul 1. https://pmc.ncbi.nlm.nih.gov/articles/PMC2769957/
Ginsberg BH. Factors affecting blood glucose monitoring: sources of errors in measurement. J Diabetes Sci Technol. 2009 Jul 1. https://pmc.ncbi.nlm.nih.gov/articles/PMC2769960/
U.S. Food and Drug Administration. Blood Glucose Monitoring Devices. 2024. https://www.fda.gov/medical-devices/in-vitro-diagnostics/blood-glucose-monitoring-devices
Apiratmateekul N, Duanginta W, Phetree M, Kongros K, Treebuphachatsakul W. Effects of Simulated Adverse Environmental Conditions Related to Actual Conditions at Health Promoting Hospitals on the Performance of Blood Glucose Testing by Glucose Meters. J Diabetes Sci Technol. 2023 Jan. https://pmc.ncbi.nlm.nih.gov/articles/PMC9846385/
Trividia Health. TRUE METRIX® Blood Glucose Monitoring System Troubleshooting Steps. 2024. https://www.trividiahealth.com/wp-content/uploads/2024/01/Hi_012224.pdf
U.S. Food and Drug Administration. Users of Blood Glucose Meters Must Use Only the Test Strip Recommended For Use With Their Meter. 2018. https://www.fda.gov/medical-devices/blood-glucose-monitoring-devices/users-blood-glucose-meters-must-use-only-test-strip-recommended-use-their-meter
U.S. Food and Drug Administration. Self-Monitoring Blood Glucose Test Systems for Over-the-Counter Use: Guidance for Industry and Food and Drug Administration Staff. 2020. https://www.fda.gov/media/87721/download
FAQs
Can I store blood glucose test strips in the bathroom?
Bathrooms might seem like a sensible place to keep medical supplies, but they’re often one of the most humid rooms in the house because of steam from showers or hot baths. This humidity can affect the chemical components in some test strips.1 A bedroom drawer may be a better option, as long as it stays within the storage conditions recommended by the manufacturer.
Does opening the test-strip container affect the strips?
Yes. Once the container is opened, the remaining test strips are exposed to the surrounding air each time you remove a strip. The moisture that’s in the air can affect the reagents used by some test strips.1 Some test strip containers come with a desiccant which helps to absorb the moisture and keep the strips dry. Ensure to close the container straight after removing a strip, and (with dry hands) take out only the strip you’re about to use.5
Are glucose test strips all the same?
No. Glucose machine strips are designed to work with specific blood glucose meters, so you should always check that the strips you buy are compatible with your particular meter. Using incompatible strips can lead to inaccurate readings.6
