Do Expired Test Strips Read High Or Low?

man holding test strip

Do Expired Test Strips Read High or Low?

People with diabetes must maintain blood glucose levels within acceptable ranges to avoid health issues. Whether you have Type I or Type II diabetes, regular blood sugar testing is essential to avoiding higher or lower than normal glucose levels.

Depending on the type of diabetes you have, you may need to check your blood glucose levels anywhere from two to ten times a day. Your doctor makes recommendations based on the type of diabetes and how well your diabetes is controlled. 

Self-testing with diabetic test strips is the best way to monitor yourself, but testing strips are expensive and range in costs from $0.50 per strip to over $1.00 per strip, sometimes more depending on manufacturer and number of strips in a box. Cost outlay for many diabetics may reach thousands of dollars a year for just their testing strips, even for those with health insurance coverage.


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Is it safe to use expired test strips? Before you do, ask yourself a few questions about their potential effectiveness. For example:

  • How have they been stored? Have they been stuffed in the glove box of a hot car all summer? Exposed to dampness or high humidity levels?
  • How long after the expiration date can you safely use them?
  • What are the risks of using expired test strips?

Accuracy is key when testing your blood sugar. Before considering expired test strips, know the facts.

What makes those diabetic test strips so special?

Diabetic test strips are an important part of blood sugar (glucose) monitoring. They may not look so special, but these strips enable glucometer devices to ‘read’ glucose levels in the blood. These readings provide valuable information that determine whether insulin or food or liquid intake is needed to boost levels, and whether adapting activities during certain times of the day is required. Blood sugar levels rise and fall throughout the day, but diabetics must carefully monitor such changes.

Glucose test strips are primarily made of thin, flexible plastic. A small area at the tip of the strip is coated with an enzyme known as glucose oxidase. This enzyme produces gluconic acid when combined with a blood sample. After a drop of blood is placed on the strip, it’s inserted into the glucose meter device, which transmits a small current of electrons to the end of the strip.

The enzyme on the strip enables the device to ‘read’ the current between the terminals, using an algorithm to determine the glucose concentration in the blood.

Though many different brands of glucose testing strips are manufactured today, most are constructed the same way. The top layer of the strip collects the blood. The middle layer generally acts like a filter of sorts that allows the blood sample to reach the glucose oxidase as well as other stabilizing chemicals where the analysis process occurs.

The stability of the chemicals used and their longevity and accuracy differ by brand, age, and other factors. These factors are important when considering the use of expired strips.

About expiration dates

Test strip brands usually specify a Use By date. The FDA recommends that strips not be used after that date to ensure accurate results. Instructions for care and storage of test strips are provided through printed inserts or on the box itself.

Use of test strips exposed to moisture, heat, and humidity may give false results. Any temperatures outside of the recommended range provided by the manufacturer may also damage test strips and interfere with accuracy.

Always follow manufacturer guidelines for usage. Major brands suggest discarding any test strips or control solutions by the Use By date. Some glucose meters can’t read an expired strip and some manufacturers sell proprietary blood glucose monitors that only read their brand of test strips (always read the fine print on meters before purchase).

Why would you buy expired test strips in the first place?

Why risk buying expired test strips? Cost. Test strips are expensive. According to a recent New York Times article[1], insurance coverage changes often, leaving a patient with little choice other than to purchase newer monitors and their associated and often more expensive testing strips. When patients have to switch, they are often left with unused strips.

Seniors on fixed incomes may find selling their unused strips lucrative to making ends meet. Unfortunately, some people with diabetes reduce the number of times they test themselves to save money on strips. A diabetic selling his or her test strips for extra cash puts their own health at risk by not testing themselves as often as they should.

Risks of using expired testing strips

Saving money is always very important, but the FDA warns that saving money on pre-owned or expired strips may not be a safe practice in the long run. The agency recently issued a press release warning against previously owned testing strips. Doing so carries potentially increased risk of serious injury (or even death) to patients relying on accuracy of such tests to monitor and treat their diabetes.

Buying expired strips online from sites like Craigslist, eBay or independently owned ‘cash for strips’ websites is not recommended for a variety of reasons. First, test strips must be stored correctly for accurate results. This applies to new, sealed boxes as well. Improper storage of strips can result in false high or low readings which affect not only doses of insulin, but may prompt medical emergencies. You never know where these strips came from or how their previous owners stored them.

Expired or otherwise compromised test strips due to improper storage increase the risk of inaccurate readings necessary to maintain blood sugar levels. Inaccurate readings might trigger a number of medical issues such as higher than normal blood sugar (hyperglycemia). Hyperglycemia can lead to a condition known as ketoacidosis or diabetic coma, which develops when the body doesn’t have enough insulin. In such cases, the body is unable to break down and use glucose for fuel and ketones build up in the blood resulting in a medical emergency.

A false reading may also indicate that your blood sugar levels are normal when they’re actually lower than they should be. Low blood sugar levels (hypoglycemia) require prompt treatment and can be as dangerous as high blood sugar. Medical issues associated with untreated low blood sugar levels include irregular heart rhythm, visual disturbances, confusion, seizures, and loss of consciousness.

Risk of exposure to bloodborne pathogens HIV, Hepatitis, or other infections is also a possibility when purchasing pre-owned test strips from strangers or less than reputable sellers.

What about the accuracy of expired test strips?

The safety and quality of test strips bought online or even neighborhood sources is often questionable. These days, it’s not uncommon to see signs on light posts proclaiming ‘Strips for cash!’ or ‘We’ll buy your test strips’.

Some users of expired strips say they’re just as accurate as new strips, even when expired by a year or more. Others have completely different experiences. Consumers must realize that the enzymes on the strips do eventually break down. Some strips may prove effective longer than others. However, the enzymes used on testing strips differ by brand. Some manufacturers use less stable enzymes on their strips. Such factors must always be taken into consideration when purchasing expired test strips. So too must the way the strips have been stored prior to sale.

Accuracy and longevity also rely on proper storage methods. Some people follow storage instructions while others don’t. Even after expiration, a test strip may still display ‘within normal range’ for blood sugar levels, but might also start showing errors in the high and low ranges.

About legalities

Consumer Affairs reports that like selling unused food stamps (illegal), the same applies to any medical device or supply paid for through government services such as Medicare and Medicaid (CMS – Centers for Medicare and Medicaid Services).[2] How can you tell if a box of strips has been paid for by CMS? The box will have a red line on it.

The laws are gray when it comes to re-selling test strips unless they are expired, the strips have been used, or if boxes have been opened. In other words, it’s illegal to sell expired test strips.

When purchasing expired testing strips online, you also run the risk of counterfeit products. Some test strip brands (including those from other countries) have not been approved for sale by the FDA. If strips look different than those you’re used to or come in boxes with or without instructions in another language, use caution. Expiration dates for safe use of testing strips may not be visible on the box or vial they come in.


Active ingredients found on any test strip won’t be stable forever. Patients who use testing strips past the expiration date must assume the risks. Inaccurate results can have a detrimental effect on patient health and should be taken seriously.

While it’s tempting to save money buying pre-owned or expired diabetic testing strips, the need for caution and safety should not be underestimated. While some websites claim that expired or pre-owned test strips are safe to use within a certain time frame, that’s not the only factor to take into consideration before purchase. Caveat emptor – let the buyer beware.


1. What are the potential health risks associated with using expired test strips?

The use of expired or compromised blood sugar testing strips may lead to inaccurate readings, potentially causing health issues such as hyperglycemia. Hyperglycemia, in turn, can result in serious conditions like diabetic coma or ketoacidosis, especially when the body lacks sufficient insulin.

2. Are there any reliable ways to determine the accuracy of expired test strips before use?

Test strips and control solutions come with printed expiration dates on their vials. Upon opening a test strip or control solution vial, it is essential to note the discard date, calculated as the date of opening plus six (6) months, in the designated space on the label. 

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