Yes, diabetic test strips expire. To understand why diabetic test strips expire, you need to know a little bit about how they work. Test strips contain enzymes that help convert glucose into electricity—this electrochemical signal is read by your meter and translated into the number that appears on your screen. Diabetic test strips expire because these enzymes degrade over time. As the enzymes degrade, the electrochemical signal being sent to the meter will become weaker, resulting in lower readings. Test strips are also highly sensitive to heat and humidity and will expire more quickly when exposed to excess heat or humidity. Most test strip containers contain a substance that absorbs moisture to protect the test strips when they are exposed to moist climates. The substance can only absorb so much moisture before it becomes saturated so test strips need to be protected from moisture as much as possible. The amount of heat/humidity that causes an inaccurate reading varies depending on the brand of test strips. A good rule of thumb is to keep test strips between 40°F-86°F (4°C-30°C) and to limit exposure to the environment by keeping vials closed between testing and using test strips within 6 months of opening vials. Control solutions should also be used periodically to make sure you are receiving accurate readings. Control solutions, while helpful, do not provide very precise measurements. They usually come in low, normal, and high ranges. Low control solutions measure levels between ~30-60 mg/dL, normal control solutions measure levels between ~70-120 mg/dL, and high control solutions measure levels between ~250-400. As you can see these are large ranges and should not be the sole method used to determine if readings are accurate. If you don’t think you are getting an accurate reading you should test with a different meter and test strips and compare the readings or take your meter and test strips to the doctors office and have them test it against their equipment.