Blood glucose test strips are sophisticated medical tools central to the daily management of diabetes. These strips work in conjunction with a glucose meter to provide an immediate measurement of the sugar concentration in a person’s blood sample. This information is relied upon to make timely adjustments to insulin dosing, diet, and activity levels. The accuracy of these readings is paramount to maintaining safe blood sugar ranges and preventing serious complications. Manufacturers strictly advise against using expired test strips because their accuracy cannot be guaranteed.
The Science Behind Test Strip Expiration
The function of a blood glucose test strip hinges on a precise electrochemical reaction involving specialized biological catalysts. Each strip is coated with enzymes, typically glucose oxidase or glucose dehydrogenase, which react specifically with the glucose in the blood sample. This reaction converts the glucose into an electrical current, which the meter then interprets to display a numerical glucose reading.
Since these enzymes are organic proteins, they are subject to degradation over time. Exposure to environmental factors like heat, light, and moisture accelerates this breakdown, causing the enzymes to lose stability and reactivity. Once the enzymes are compromised, the chemical reaction with glucose is altered, and the resulting electrical signal sent to the meter is inaccurate. The expiration date represents the final point at which the manufacturer can guarantee the chemical integrity of this enzymatic system.
The Consequences of Inaccurate Readings
Using expired or compromised test strips can lead to readings that are significantly inaccurate, which poses a substantial risk to health management. The results can be unpredictable, sometimes being falsely high and other times falsely low, making it impossible to know the true glucose level. Relying on these unreliable numbers can lead to dangerous errors in treatment decisions.
A falsely high glucose reading can prompt a person to administer too much insulin or other glucose-lowering medication. This over-correction can lead to hypoglycemia, a life-threatening condition where blood sugar drops dangerously low, causing symptoms like confusion, seizures, and loss of consciousness.
Conversely, a falsely low reading may cause a person to believe their glucose is within a safe range, leading them to delay or skip a necessary insulin dose. This under-correction results in severe hyperglycemia, where blood sugar remains dangerously high. Sustained, severe hyperglycemia increases the risk of diabetic ketoacidosis (DKA), a medical emergency where the body produces excess blood acids called ketones. DKA can lead to a diabetic coma and even death if not promptly treated.
Storage and Handling to Maximize Shelf Life
While test strips have a fixed shelf life, proper storage can ensure they remain accurate until the printed expiration date. The primary enemies of the enzymatic coating are heat, humidity, and light.
It is recommended to store test strips in a cool, dry, and dark environment, ideally within a temperature range of 68°F (20°C) to 77°F (25°C). Users should always keep the strips in their original vial, which is designed to protect them and often contains a desiccant to absorb moisture. It is crucial to tightly close the cap immediately after removing a strip to prevent exposure to air and humidity. Avoid common storage locations like bathrooms, which are highly humid, or cars, which experience extreme temperature fluctuations. Many manufacturers also specify a separate “use-by” period, typically three to six months, after the vial is first opened.