The question of whether to use medical supplies past their expiration date is common, especially for conditions requiring frequent testing, such as diabetes management. Blood glucose test strips are a frequent source of this dilemma. Unlike many products with conservative expiration dates, diagnostic tools rely on precise chemical reactions that degrade over time. Since inaccurate results directly affect medication dosing, the date printed on the vial serves as the manufacturer’s guarantee of a scientifically reliable reading.
The Chemical Process of Test Strip Degradation
Blood glucose test strips function through an electrochemical process involving specialized biological components. The strip surface contains an enzyme, most commonly glucose oxidase (GOx), which initiates the reaction. When blood is applied, GOx catalyzes the oxidation of glucose, converting it into gluconic acid and hydrogen peroxide. This chemical change produces a measurable electrical current, which the glucose meter detects and translates into a numerical blood sugar value. The expiration date guarantees the stability of this enzyme system, as GOx naturally breaks down over time, losing its ability to catalyze the reaction efficiently. The strips are also highly sensitive to environmental factors like humidity, heat, and air exposure. Moisture and high temperatures accelerate the degradation of the enzyme and other components, compromising the strip’s ability to produce an accurate current.
Impact on Reading Reliability and Accuracy
The chemical degradation within an expired strip directly translates into unreliable blood glucose readings. As the enzyme activity weakens, the electrical current generated for a given glucose concentration becomes inconsistent. This inconsistency means the reading provided by the meter can drift significantly from the actual glucose level in the blood. A meter is calibrated to interpret a specific electrical signal as a certain glucose concentration, assuming a fully functional strip. When a compromised strip produces a weaker or non-standard current, the meter cannot detect the underlying chemical fault; it simply reports the number corresponding to the current it receives. This results in a high standard deviation for the reading, meaning the result is not trustworthy. Expired strips can produce results that are either falsely high or falsely low, and there is no reliable way for the user to predict the direction or magnitude of the error. The loss of accuracy is a failure of the measurement system’s intended function.
Health Risks Associated with Inaccurate Results
Relying on readings from compromised test strips creates a risk to patient health, as treatment decisions are based entirely on the reported number. The danger is twofold, depending on whether the inaccurate reading is a false high or a false low.
A reading that is falsely low suggests the blood glucose is lower than it actually is. If a person interprets this result as low, they may over-treat the perceived low blood sugar by consuming extra carbohydrates or administering too much insulin. This action can precipitate a severe hypoglycemic episode, involving dangerously low blood sugar levels that can lead to seizures, loss of consciousness, or coma.
Conversely, a falsely high reading suggests the blood glucose is elevated when it might be within a target range. In this situation, the patient might unnecessarily increase their insulin dose. A greater danger is a falsely low reading when the actual blood sugar is high, which can lead to under-dosing or missing necessary medication. Under-dosing insulin when blood sugar is high can lead to sustained hyperglycemia. If prolonged, this can trigger diabetic ketoacidosis (DKA), a life-threatening acute condition involving a dangerous buildup of blood acids called ketones.
Inaccurate readings also compromise long-term diabetes management by making it impossible to track true blood sugar trends, leading to poor overall control and increasing the risk of chronic complications.
Guidelines for Storage and Safe Disposal
To maximize the reliability of test strips before their printed expiration date, proper storage is essential. Strips should always be kept in their original container, and the lid must be immediately and tightly closed after removing a strip. This practice protects the chemical components from external factors, especially atmospheric moisture and oxygen, which accelerate degradation. The strips should be stored at room temperature, away from extremes of heat or cold. Areas like bathrooms, which experience high humidity fluctuations, or glove compartments in cars, which can get extremely hot, should be avoided. Furthermore, some meters require the user to input a code or match a code to the strip vial, and this step must be performed correctly to ensure the meter is calibrated for that specific batch of strips.
For strips that have expired or are no longer needed, safe disposal is necessary. Used test strips, along with lancets, should be placed in a puncture-proof container, such as a designated sharps container or a heavy-duty plastic bottle with a secure lid. It is important to follow local community guidelines for the disposal of medical waste, as procedures vary for ensuring these items are handled safely and responsibly.