Przeterminowane paski testowe: Jak długo są one faktycznie dokładne?

It happens to many of us. You feel refreshed and absolutely fine, but when you check your blood sugar, the reading doesn’t make sense. It may be too high or too low, and you may wonder whether your diabetes has really worsened. Something feels off. 

There could be many reasons for getting a false reading. One possible reason could be using expired blood sugar test strips. This article explains why you should never use strips that have expired.

Do Blood Sugar Test Strips Expire?

Yes, blood sugar test strips have a specific expiry date, after which you should not use them. In fact, they are medical devices with a limited shelf life. 

The U.S. Food and Drug Administration (FDA) advises against using expired strips. The agency warns that strips that are stored improperly or exposed to heat and humidity can get damaged even before the expiry date [1]. The American Diabetes Association (ADA) thus recommends that only unopened and unexpired vials of test strips should be used for accurate blood glucose readings [2]. 

Why Test Strips Expire?

A glucose test strip is a small chemical tool. Each strip contains an enzyme (usually glucose oxidase or glucose dehydrogenase) and other reagents. When blood touches the strip, the enzyme reacts and generates a tiny electrical signal. The meter then converts that signal into a number.

Over time, the chemicals in the strip degrade due to environmental factors like humidity, temperature, and sunlight (check the label). The enzyme becomes less active, and the reagent layer is exposed to moisture. Heat and air exposure (for example, leaving the vial open) can further speed up this damage. Because of these processes, test strips have a defined shelf life and an “open-vial” use duration. Manufacturers perform stability studies under different temperatures and humidity levels to set those dates. There is no validated “grace period” beyond the printed date [3]. 

The Real-World Problem with Storage

A 2021 study simulated storage of test strips in high temperature and humidity conditions similar to those seen at healthpromoting hospitals in Thailand. The median differences in glucose measurements with stressed strips were significantly different from controls. Average storage temperatures exceeded 30°C (86°F) and relative humidity averaged 84%. The researchers concluded that adverse environmental conditions led to poor performance with blood glucometers [4].

According to the FDA, manufacturers should perform stability studies for both closedvial (shelf life) and openvial conditions at different combinations of temperatures and humidity. Heat and moisture degrade the potency of reagents and increase the risk of incorrect readings. That is why ensuring adequate storage conditions for test strips is not a “nice to have” but a “must have” for accuracy [5].

Why Accuracy Matters?

A false high or low blood sugar reading can lead to a wrong decision. Too-low readings may hide hyperglycemia, while too-high numbers can prompt you to increase the dose of insulin unnecessarily. The FDA warns that incorrect results from expired test strips may lead to serious harm and instructs users to close the bottle cap as soon as a strip is removed [6].

Quick Safety Checks

• Check the date: Look at the printed expiry date every time you open a new vial and before testing.
• Keep the cap tight: Strips belong in their original vial. Close the cap immediately after removing one strip.
• Store the vial in a cool and dry place: Avoid bathrooms, kitchens, cars and direct sunlight. Keep strips at room temperature (between 4°C and 30°C).
• Re‑test if something feels off: If symptoms and the reading do not match, test again with a new strip and, if needed, compare with a laboratory result.
• Use control solution only as a basic check: Control solution can verify that the meter and strips can read a known value, but it is not a guarantee of accuracy across all glucose levels.

When to Replace Your Strips

Replace your blood sugar test strips immediately if you notice:

• Readings that do not match your symptoms
• Error messages on your meter
• Strips past the printed expiration date
• Vials opened longer than the manufacturer's recommended window
• Visible damage or moisture inside the vial

Frequently Asked Questions (FAQs)

Do blood sugar test strips expire even if sealed? 

Yes, shelf-life studies show that even closed vials have a limited “good-to-use” period. After that, the enzyme and other chemical reagents start to deteriorate. The expiry date shows how long the manufacturer guarantees the accuracy of the test strips [3].

Can expired strips read high or low? 

They can do either. Enzyme degradation and moisture damage may reduce the current and yield falsely low readings, or electrode drift may give falsely high values. There is no predictable pattern, which is why they should not be used [5].

What storage mistakes ruin strips fastest? 

Leaving the vial open, exposing strips to humidity, storing them in a hot car or a bathroom, or transferring them to another container [5].

What should I do if my reading does not match how I feel? 

Wash your hands and retest with a new strip. If the reading still seems wrong, use a fresh vial and contact your GP for a laboratory testing.

Is “opened too long” different from “expired”? 

Yes. Opened too long" means the strips or the vial has already past the manufacturer's recommended discard window, "Expired" means past the printed shelf-life date. Follow the instructions on your product. 

Switch to Fresh Strips You Can Trust

If you are getting odd readings on your blood glucometer, the best solution is to start with a fresh vial. Make sure you are storing it in a cool and dry place and the cap is airtight. 

Sinocare is a global leader in diabetes care and offers reliable test strips and blood glucose monitors. Our products are designed for accuracy and ease of use and have clear labeling and instructions. 

The company was founded in 2002 in Changsha, China and currently ranks No. 1 in China and No. 4 worldwide in the blood glucose monitoring market. It serves over 25 million users across 135 countries and regions. 

Explore Sinocare’s products to learn about our commitment to diabetes care.

References

1. U.S. Food and Drug Administration. How to Safely Use Glucose Meters and Test Strips for Diabetes [Internet]. Silver Spring (MD): U.S. Food and Drug Administration; 2021 Nov 1. Available from: https://www.fda.gov/consumers/consumer-updates/how-safely-use-glucose-meters-and-test-strips-diabetes 
2. ElSayed NA, Aleppo G, Aroda VR, Bannuru RR, Brown FM, Bruemmer D, Collins BS, Hilliard ME, Isaacs D, Johnson EL, Kahan S. 7. Diabetes technology: standards of care in diabetes—2023. Diabetes Care. 2023 Jan 1;46(Supplement_1):S111-27.
3. U.S. Food and Drug Administration. Blood Glucose Monitoring Devices [Internet]. Silver Spring (MD): U.S. Food and Drug Administration; 2024 Nov 14. Available from: https://www.fda.gov/medical-devices/in-vitro-diagnostics/blood-glucose-monitoring-devices 
4. 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. Journal of Diabetes Science and Technology. 2023 Jan;17(1):125-32. 
5. 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 [Internet]. Silver Spring (MD): Food and Drug Administration; 2020 Sep 29. Available from: https://www.fda.gov/media/87721/download 
6. ElSayed NA, Aleppo G, Aroda VR, Bannuru RR, Brown FM, Bruemmer D, Collins BS, Hilliard ME, Isaacs D, Johnson EL, Kahan S. 7. Diabetes technology: standards of care in diabetes—2023. Diabetes Care. 2023 Jan 1;46(Supplement_1):S111-27.