The accuracy of your meter results depends, in part, on how well you follow the steps for testing. Feeling a little rusty? Read on for the top 10 testing tips.

1. Wash your hands.
The single most important step you can take to get a trustworthy reading is to use good ol’ soap and water before you prick your finger. “We’re concerned about whether there might be some residue from eating a piece of fruit or perhaps some lotion on your hands. That can affect the test,” says Marlene Bedrich, RN, MS, CDE, program coordinator for the University of California Diabetes Teaching Center.

2. Use alcohol.
When you’re stuck somewhere without a sink in sight, rubbing alcohol will do the trick. Use it in place of hand washing to clean the finger, removing any residue before you test. Alcohol-drenched swabs or hand sanitizer will work. But there’s no need to use alcohol after washing your hands.

3. Dry your hands.
Whether you wash your hands or use an alcohol swab before testing, be sure to dry thoroughly. Excess water and rubbing alcohol can dilute your blood sample, affecting your reading.

4. Use a second drop.
Imagine this: You’re on a hike and need to test your blood glucose, but your fingers are covered in dirt, sap, and juice from the peach you ate earlier. There’s nowhere to wash your hands, and you’ve forgotten alcohol swabs. Your best option: Prick your finger and wipe the first drop of blood away with a clean tissue or garment. Test with the second drop of blood, which is less likely to be contaminated.

“Some people think even when [alcohol] dries, you should get a drop of blood on your finger and use the second drop, because you’ll have a little bit of alcohol that might still be on the finger and affect the results,” says Janie Lipps, APRN, BC, CDE, director of diabetes and obesity clinical trials management at Vanderbilt University Medical Center.

5. Test on your finger.
Some meters allow for pricking alternate sites that may be less sensitive to pain than the fingers, such as a palm or forearm. But results from such sites don’t reflect your current blood glucose level. “The blood circulation to the rest of the arm takes longer than it does to the fingertips,” says Bedrich. “So there’s a lag between what the blood sugar reading on the arm is versus what it is in the fingers.”

Most of the time, readings from alternate-site tests are OK to act on, but only a finger test will do if your blood glucose is changing rapidly. For example, when your blood glucose is rising (for instance, after a meal), falling (if your insulin is peaking), if you think you’re having a low, or if you have hypoglycemia unawareness, prick your finger.

6. Don’t squeeze.
Getting a large enough blood sample is important—meters won’t display a reading if there’s not enough blood on the test strip—but squeezing and rubbing your finger after you’ve pricked it can affect the blood sample. “Sometimes you’ll get a little more interstitial fluid [the substance just below the skin] than the capillary blood,” says Lipps. Washing with warm water will increase blood flow to the fingers, making it easier to get blood without pressure.

7. Get the code.
Many meters don’t require coding, but if yours does, you’ll need to input a number or use a “key” or “chip” each time you open a new bottle of test strips. Any time you think your meter is making mistakes, make sure your meter has the code from your current test strip bottle.

8. Use control solution.
If you get a reading that seems out of whack—maybe your number is extremely high after a daily run that usually lowers your blood glucose—test how well the meter is working with its strips by using the meter’s control solution. If you can’t find your meter’s brand of solution at the pharmacy, ask your pharmacist to order it.

First off, make sure your control solution isn’t expired (an open vial is good for only 90 days or the expiration date, whichever comes first). You’ll use the solution in place of a blood sample to test the glucose level. The acceptable range of glucose for that solution is listed on the back of your test strip vial or control solution. If your meter is working properly, the number it shows should fall within that range.

In the unlikely event the control solution test reveals a faulty meter or strips, call your meter company. It will usually replace your meter free of charge and collect the old one to determine what went wrong.

9. Use the right test strips.
There’s only one rule when it comes to old strips: Trash ’em. “Just because one in the bottle seems to work OK, I wouldn’t use strips that are outdated,” says Bedrich. “I wouldn’t be confident that they are reliable.”

Using the correct strips and storing them properly also are important. Using strips that aren’t approved for your meter can lead to incorrect readings. And improperly stored strips will yield poor results, too. “Some people will carry them loose in their pocket or in their kit because they don’t want to have the bulky vial that they come in,” says Bedrich. That’s a big no-no because the strips will be exposed to light and air, which can cause invisible damage.

10. Protect your supplies.
Don’t store your meter and strips where it’s too hot, too cold, too humid, or too high in altitude (meters and strips should perform in pressurized airplanes, though). Once you return the meter to a normal temperature, humidity, or altitude, however, it should be back to normal. Still, you’ll want to plan for such environmental changes, using an insulated container (a resealable plastic bag will help keep strips and meter dry inside).