Taking your blood glucose involves pricking your finger with a small needle, applying a drop of blood to a test strip, and reading the result on a handheld meter. The whole process takes under a minute once you get the hang of it. Here’s exactly how to do it, with tips to get accurate readings and minimize pain.
What You Need
A standard blood glucose kit includes a handheld meter, test strips, lancets (tiny single-use needles), and a lancing device that holds the lancet and controls how deep it goes. Test strips contain enzymes that react with glucose in your blood and produce an electrical signal the meter converts into a number, displayed in mg/dL. Most kits also come with a control solution you can use to verify the meter is reading correctly, which is worth doing when you open a new box of strips or if your results seem off.
Step-by-Step Process
Start by making sure your meter is charged and has a fresh test strip inserted (or ready to insert, depending on the model). Then follow these steps:
- Wash your hands with warm, soapy water and dry them thoroughly. This matters more than most people realize. Residue from food, lotion, or even fruit juice on your fingers can skew your reading. Warm water also helps increase blood flow to your fingertips.
- Massage or shake out your hand to get blood moving into your fingers. Letting your arm hang at your side for a moment works too.
- Prick the side of your fingertip with the lancing device. Avoid the very center of the pad.
- Squeeze gently from the base of your finger to form a small, round drop of blood. Don’t smear it.
- Touch the drop to the test strip and let it absorb. Most strips draw the blood in automatically through a small channel.
- Wait a few seconds for your reading to appear on the meter’s screen.
- Record your result. Many meters store readings automatically, but keeping a log with notes (what you ate, how you felt, whether you exercised) helps you and your doctor spot patterns.
- Dispose of the lancet and strip. Never share lancets with anyone, even family members.
When to Test
How often you check depends on your type of diabetes and whether you take insulin. The most common testing times are: first thing in the morning before eating or drinking anything, before meals, two hours after a meal, and at bedtime. That fasting morning reading is particularly useful because it reflects your baseline glucose without food in the picture.
If you have type 1 diabetes, take insulin for type 2, or frequently experience low blood sugar, your doctor may want you testing more often, including before and after physical activity. People newly diagnosed or adjusting medications often test more frequently until their numbers stabilize.
Why Hand Washing Matters for Accuracy
Meter manufacturers recommend soap and warm water over alcohol wipes for a reason. Alcohol can interfere with the enzyme reaction on the test strip and potentially lower your reading. Research comparing the two methods found that if you do use alcohol, waiting at least 30 seconds for it to fully evaporate eliminates the effect on accuracy. But pricking a still-wet finger, whether wet from alcohol or water, produces measurably lower readings.
The simplest rule: wash with soap, dry completely, then test. Skip the hand sanitizer. It dries and tightens the skin, which also makes the prick more painful.
How to Make It Hurt Less
The side of your fingertip has fewer nerve endings and more blood vessels near the surface than the pad. Pricking the side rather than the center is the single biggest change you can make for comfort, and you’ll typically get a better blood drop too.
Most lancing devices have an adjustable depth dial. Start at the shallowest setting and only go deeper if you’re not getting enough blood. Deeper pricks hurt more and don’t improve accuracy. Use a fresh lancet every time. Reusing them dulls the needle, which tears the skin instead of piercing it cleanly.
Rotate which finger you use. Some people assign different fingers to different days of the week so no single spot gets overworked and sore. If you’re struggling to get enough blood, rub the finger you plan to prick until it feels warm, or shake your hand down at your side for a few seconds. Some people wrap a rubber band loosely around the middle joint of the finger to encourage blood to pool at the tip, then remove it right after pricking. Certain meters also allow testing on the forearm or thigh, which can be less sensitive than fingertips.
Common Reasons for Error Codes
If your meter flashes an error instead of a number, the most likely culprits are a blood sample that was too small or smeared across the strip, a test strip that wasn’t inserted correctly, an expired or wrong-brand strip, or strips that were stored somewhere too hot or too cold. Test strips are sensitive to temperature and moisture. Keep them in their original container with the lid closed, and check expiration dates regularly.
If your readings seem unusually high or low and don’t match how you feel, test again with a new strip. You can also use the control solution that came with your kit to verify the meter and strips are working properly.
Disposing of Lancets Safely
Used lancets are considered sharps, and tossing them loose in the trash risks needle sticks for anyone handling the bag. The FDA recommends placing lancets in a sharps disposal container immediately after use. You can buy these at most pharmacies, or use a heavy-duty plastic container like a laundry detergent bottle with a screw-on lid.
When the container is about three-quarters full, seal it and dispose of it according to your local guidelines. Options vary by location but typically include drop-off boxes at pharmacies, hospitals, or fire stations, household hazardous waste collection sites, and mail-back programs. Your local health department or trash service can tell you what’s available in your area. Never overfill a sharps container, and don’t reuse one that’s been sealed for disposal.