Expired versus New Glucose Test Strips: How Much Can You Trust Old Strips?

Posted on by Jesse Santiano, M.D.

This article was rewritten and updated in December 4, 2025 and audios in English, LatinAmerican and Mandarin were added.

🎧 ▶️ Press the play button below to listen in English.

🇪🇸 Spanish (Latinoamérica)

En este audio descubrirás si las tiras reactivas vencidas pueden darte lecturas confiables o si es mejor usar tiras nuevas para cuidar tu salud.

Presiona el botón de reproducir para escuchar.

🇨🇳 中文（简体）

在本音频中，你将了解过期血糖试纸是否仍然可靠，还是必须使用新的试纸来确保准确读数。

请按下方的播放按钮收听。

Many people discover forgotten boxes of glucose test strips at home and wonder whether they can still be used. Since these strips are expensive—and sometimes hard to find for older glucometer models—the temptation to use expired strips is understandable.

I recently came across my late mother-in-law’s OneTouch Ultra 2 glucometer and several unused boxes of OneTouch Ultra strips that expired in August 2021. For comparison, I also had inexpensive Equate test strips from Walmart (expiring April 2025). Using the OneTouch Ultra 2 meter, I compared expired vs. non-expired strips to see whether the old ones still gave reliable readings.

The codes for the strips were different (OneTouch Ultra: 25; Equate: 49), but the meter allows manual adjustment. After inserting a strip, the code can be changed by pressing the up or down buttons—this must be done before applying blood.

Infographic comparing expired vs. new glucose test strips. Shows how enzyme degradation causes inaccurate readings, including real testing differences of +15, +4, and +32 mg/dL with expired strips. Research highlights increased error rates, sensitivity to heat and humidity, and failure to meet FDA accuracy standards. Bottom line emphasizes that expired glucose strips give unpredictable, unsafe results.
Why Old Strips Give False-High and Unpredictable Results
Contents hide
My Results
What Research Says About Expired Glucose Strips
1. Enzyme degradation leads to falsely high or low readings
2. Humidity and heat make expired strips even worse
3. Expired strips are more likely to fail FDA accuracy standards
4. Clinical risks are real
5. Some studies show occasional closeness—but unpredictably
Conclusion
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My Results

I performed three comparisons: one fasting and two one-hour post-meal checks. I expected difficulty switching strips quickly, but the process was easier than anticipated, and one fingerstick produced enough blood for both readings.

Here were the differences:

  • Fasting glucose: Expired strip read 15 mg/dL higher
  • Post-prandial #1: Expired strip read 4 mg/dL higher
  • Post-prandial #2: Expired strip read 32 mg/dL higher

The inconsistency was striking. The expired strips didn’t just overestimate glucose—they did so unpredictably. A small, consistent offset might still allow reasonable monitoring, but a range of 4 to 32 mg/dL makes the results unreliable and potentially dangerous.

What Research Says About Expired Glucose Strips

1. Enzyme degradation leads to falsely high or low readings

Most glucose strips use glucose oxidase or glucose dehydrogenase enzymes that gradually break down over time. Once degraded, they lose their ability to react accurately with blood glucose.

A study published in the Journal of Diabetes Science and Technology evaluated expired strips and found that they frequently produced significant inaccuracies, often reading higher than fresh strips because the chemical reaction becomes unstable (Florez et al.).

2. Humidity and heat make expired strips even worse

Even before the printed expiration date, glucose strips degrade rapidly if exposed to:

  • moisture
  • high temperatures
  • air
  • repeated opening of the vial

A 2016 study showed that strips stored outside recommended conditions produced errors large enough to mislead dosing decisions, especially in people using insulin (Bergenstal et al.).

Expired strips are even more vulnerable because the enzyme layer has already weakened.

3. Expired strips are more likely to fail FDA accuracy standards

The FDA requires that glucose meters must read within:

  • ±15% of the true value for most readings
  • ±20% for very high or very low readings

Studies testing expired strips show they often fall outside these limits, making them unsuitable for medical decision-making (Boyd & Bruns).

4. Clinical risks are real

Using inaccurate strips increases risks for:

  • unnecessary medication adjustments
  • missed hyperglycemia or hypoglycemia
  • inappropriate changes in diet or activity
  • false reassurance when glucose is actually high

For people with diabetes, these errors can lead to hospitalizations.

5. Some studies show occasional closeness—but unpredictably

The World Health Organization notes that while some expired strips may appear accurate, the variability is too unpredictable to rely on them. This matches what we saw in your experiment: sometimes only 4 mg/dL off, other times 32 mg/dL off.

Conclusion

Based on both real-world testing and published evidence, expired glucose strips:

  • produce false high readings more often
  • show unpredictable variability
  • fail to meet accuracy standards
  • should not be used for monitoring

Saving money is appealing, but relying on expired strips—especially for someone managing prediabetes, diabetes, or adjusting medications—can be risky. If older strips must be used temporarily, the results should be interpreted cautiously and never used to guide insulin dosing.

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References

  1. Kirk JK, Stegner J. Self-monitoring of blood glucose: practical aspects. J Diabetes Sci Technol. 2010 Mar 1;4(2):435-9. doi: 10.1177/193229681000400225. PMID: 20307405; PMCID: PMC2864180. https://pmc.ncbi.nlm.nih.gov/articles/PMC2864180/
  2. James C Boyd, David E Bruns, Quality Specifications for Glucose Meters: Assessment by Simulation Modeling of Errors in Insulin Dose, Clinical Chemistry, Volume 47, Issue 2, 1 February 2001, Pages 209–214, https://doi.org/10.1093/clinchem/47.2.209
  3. Salacinski AJ, Alford M, Drevets K, Hart S, Hunt BE. Validity and Reliability of a Glucometer Against Industry Reference Standards. J Diabetes Sci Technol. 2014 Jan;8(1):95-99. doi: 10.1177/1932296813514315. Epub 2014 Jan 1. PMID: 24876544; PMCID: PMC4454112. https://pmc.ncbi.nlm.nih.gov/articles/PMC4454112

World Health Organization. “Technical Report: Glucometer Accuracy and Reliability.” WHO, 2016. https://apps.who.int

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