Here's some tips about test strips, and testing in general.
There are so many different meters so read the instructions for yours, but here are some general tips:
Storage of strips: Heat, humidity, temperature and exposure to air can all affect strips. I recall a person whose test vial was left open to the air (not humid or hot air) but the readings were over 100% off from the lab! (Making them read REAL high). When this person switched to a new vial of diabetes test strips, the sugar readings plummeted to normal (and the meter checked accurate against the lab).
Store Test Strips at a temperature less than 86�F (30�). DO NOT FREEZE.
DO NOT expose Test Strips in direct sunlight.
Control solution: Call some of us skeptics, but a lot of people do not trust the control solutions that come with the blood sugar monitors. Why? Well, the control solutions are not your blood. They offer up a broad "range" of blood sugars which are "OK" for your meter to test at. Also, once opened, the control solutions will maintain their values for only 3 months or less depending on temperature and evaporation. So, there you have it. Check your glucose meter out against the real thing - your blood. Do a meter comparison when you have a blood test done (but don't use the same arterial blood because it won't work. Bring your meter, poker and a test strip along and test as you do at home.)
Is blood sugar monitor coded correctly? According to a study of 201 users of blood sugar meters, about 16% had improperly coded diabetes test strips. A study by Bayer showed that miscoded strips are inaccurate over 90% of the time. Sometimes by as much as 43%! So a test of 110 mg/dL or 6.1 mmol could show as 157 mg/dL or 8.7 mmol (or the other way around!) Check to see if the code on the vial of diabetes test strips matches the code number on the display screen when the glucose meter is turned on. Meters are "coded" to match a particular batch of diabetes test strips. This calibration can be done by entering a code number into the meter or by inserting a code chip. Some diabetes test strips have the coding build in (like the Compact and many of the Ascencia meters). But, many of the popular meters by Lifescan and Freestyle don't. You need to "code" or "calibrate" your meter each time you open a new vial of diabetes test strips. A lot of us no longer have to code, but if you do this is a BIG reason for "Why are my numbers so high" questions on the boards.
Loose diabetes test strips. If you take individual diabetes test strips into your purse or wallet this can affect the accuracy (unless they are foil-wrapped from the manufacturer). Also, try not to move the few remaining strips of one vial into the new vial you are opening if the code numbers don't match. And if you have one vial of diabetes test strips at home and one vial at work but just use the one meter - make sure the vials have the same coding. WAIT!!! Ahhh. . . and one more thing. Even if the strips have the same code, they may have different expiration dates! After transferring a few strips a couple of times, you could end up with some pretty outdated strips floating around in a vial!
Age of blood sugar monitor: Old blood sugar monitors may be inaccurate simply because of age. But old diabetic meters also tend to need cleaning or the dirt/dried blood could affect the accuracy of the reading. Be sure to follow cleaning instructions from the manual to ensure accurate results. If you have a diabetic meter older than 5 years please consider calling the meter company (often there is a 1-800 # on the back of the meter) and asking for a free updated model. They should want to keep you as a customer buying their strips.
Expired diabetes test strips? Check the expiration date when the pharmacy gives you the diabetes test strips. If you don't feel you'll be using them before that date, ask for another batch with a later date. A few times I've heard people complain about the pharmacy selling them strips that outdated the next month.
Correct unit of measurement: Be sure to check that your machine is reading in the unit of measurement you are accustomed to. The U.S. uses mg/dl whereas Canada and most other countries use mmol/L. Sometimes the blood sugar monitor can read in either unit and it might accidentally be switched. Check beside the actual number that shows up on the screen to see the unit of measurement. If not correct, visit your manual for instructions to change it or call the 1-800# on the back of the meter. (FYI to convert from mmol/L to mg/dl you divide by 18. To covert from mg/dl to mmol/L you multiply by 18).
Hi and Low: Know what the "Hi" or "Low" means if you see it on your machine. Each meter can be different. "Hi" for some blood sugar monitors might mean over 540 mg/dl or 30 mmol/L!! At the "LOW" reading, this is far lower than what we recommend for target blood sugars. If "Low" you should treat with fasting acting sugar like glucose tabs.
Underfilled? Most newer meter have under-fill detection of some sort. However, the old Elite used to beep after a few seconds even if the chamber wasn't full. People were getting readings lower than anticipated. Also, the Compact meter tends to "err" and waste strips if you don't hold your finger there long enough. It's a good practice to hold your finger to the strip for 1-2 seconds after the beep to avoid wasting diabetes test strips because of under fill.
Date vial opened? For some diabetes test strips, once you open the vial you should use the content of the vial within 3 months no matter what the expiration date (because of repeated exposure to air). The Accusoft products have lid with a preservative in it so are supposedly good up until the actual expiration date on the bottle. However, other vials of strips (like Ultra, Freestyle) are good for a limited time once the lid is opened (regardless of the date). Check the information in your diabetes test strip box to be sure.
Storage of meter: Don't leave blood sugar monitors in the car on hot or freezing days. They are just tiny little devices and you know how tempermental electronics are.
Now here's some other things that could affect your reading:
Hands washed?: Always wash your hands before testing, and dry completely. Even if you think they're clean they might not be. Here are things from past posts: banana (no- not the peel the white yummy stuff); glucose tablet (I know - you're saying "duh". But I forgot and my finger felt clean.) and a drip of apple juice from the apple. If you get a "wonky" number wash your hands and do another glucose test to double check.
Arm or finger poke site? Some alternate site meters suggest that if you suspect your are having a low blood sugar or hypoglycemia you should not poke your arm. Instead, you should use your finger. Please read your meter insert carefully. Post prandial blood sugars, or those done after meals, may not be as accurate on the arm either. If in doubt, use your finger. Most of us recommend the finger. AND NEVER TEST ON THE TIP !!!!! test on the sides above the first joint instead. There are less nerve endings there and it gives you twice as many sites to rotate (always rotate testing sites). See my "Tearless Testing post in the Type-2 Achieves".
Thickened blood caused by dehydration might effect results. It's always a good idea to stay hydrated anyway.
Some drugs can affect the results:
Treatment of blood with EDTA or Heparin or other blood thinners should not effect results
Acetaminophen, salicylate, ibuprofen and ketoprofen occurring in expected blood concentrations should not effect results
However check with your doctor or pharmacist (your best choice) to see if any medications you are given could affect the result.