Testing your blood sugar at home takes about 30 seconds once you have the supplies ready. The process involves pricking the side of your fingertip with a small needle called a lancet, placing a drop of blood on a test strip, and letting a meter display your reading. Most people get comfortable with it within a few days.
What You Need Before You Start
A basic blood sugar testing kit includes a glucose meter, test strips designed for that specific meter, a lancing device, and lancets. Test strips are the ongoing cost: they come in sealed containers and need to stay dry and at room temperature. Damaged or expired strips give unreliable readings, so check the date on the container before each use.
Your lancing device will have adjustable depth settings, typically numbered from zero to five. A lower number gives a shallower poke, and a higher number goes deeper. If you have thicker or calloused skin, you may need a higher setting to get enough blood. Start in the middle range and adjust from there. The goal is the shallowest depth that still produces a usable drop of blood.
Step-by-Step Finger-Prick Testing
Wash your hands with soap and warm water, then dry them completely. This step matters more than you might think. Food residue, lotion, or even traces of fruit on your fingers can produce a falsely high reading. Don’t substitute hand sanitizer for handwashing, and if you use an alcohol wipe, let the skin dry fully before pricking.
Shake or massage your hand gently to encourage blood flow to your fingertips. Insert a fresh test strip into the meter so it’s ready. Then prick the side of your fingertip with the lancet. The side hurts less than the pad because it has fewer nerve endings.
Squeeze gently from the base of your finger to form a small, round drop of blood. Touch the edge of the test strip to the drop. Don’t smear the blood or try to add a second drop after the first one is applied, as this can throw off the reading. Within a few seconds, your blood sugar level will appear on the meter’s screen.
Record the result along with the time and any notes about what might have affected it, such as a recent meal, exercise, or stress. Many meters store readings automatically, and some sync to a phone app.
When and How Often to Test
Testing frequency depends on your type of diabetes and treatment plan. People using insulin typically test multiple times a day: before meals, before bed, and sometimes in the middle of the night. If you manage your diabetes with oral medication or lifestyle changes alone, you may need to test less frequently.
The timing of your test determines what the number means. The American Diabetes Association suggests these targets for most nonpregnant adults with diabetes:
- Before a meal: 80 to 130 mg/dL
- One to two hours after the start of a meal: less than 180 mg/dL
A reading below 70 mg/dL is considered low blood sugar. Below 54 mg/dL is classified as severely low and needs immediate treatment. If you get a reading that doesn’t match how you feel, wash your hands and test again before reacting to the number.
Testing on Sites Other Than Your Fingertip
Some meters allow you to test using blood from your forearm, upper arm, the base of your thumb, or your thigh. This can give your fingertips a break, especially if you test frequently. However, these alternative sites are less reliable when your blood sugar is changing quickly, such as after eating, after taking insulin, during exercise, or when you’re sick or stressed.
Stick with your fingertip if you suspect your blood sugar is low, if you don’t usually feel symptoms when it drops, or if the alternative-site reading doesn’t match how you feel. Not every meter supports alternative-site testing, so check your device’s instructions before trying it.
Continuous Glucose Monitors
A continuous glucose monitor, or CGM, is a small sensor you wear on your body that checks your glucose levels automatically throughout the day and night. It reduces or eliminates the need for finger pricks.
To apply one, wash the sensor site and your hands with soap and water, then let the skin dry completely. Avoid moisturizing soap or lotion, which can prevent the adhesive from sticking. The sensor inserts with a quick press that feels similar to a finger prick, but most people stop noticing it once it’s in place. CGM sensors need to be replaced every 7 to 14 days, and rotating the placement site helps prevent skin irritation.
What Causes Inaccurate Readings
The most common source of error is residue on your hands. Handling fruit, juice, or sugary foods before testing can inflate your reading significantly, even if your hands look clean. Washing with soap and water solves this.
Other factors that affect accuracy include extreme temperatures (keep your meter and strips at room temperature), dehydration, and anemia, both of which alter the concentration of red blood cells in your sample. Make sure the test strip is fully inserted into the meter, and always use strips designed for your specific device. Strips from a different brand or model won’t give reliable results even if they physically fit.
If a reading seems off, the simplest troubleshooting step is to wash your hands, use a fresh strip, and test again from your fingertip.
Safe Lancet Disposal
Used lancets are sharp enough to puncture skin and should never go loose into a regular trash bag. Place each used lancet into a sharps disposal container immediately after use. You can buy one at most pharmacies, or use a heavy-duty plastic container with a screw-on lid, like a laundry detergent bottle. Keep the container out of reach of children and pets, and stop filling it when it’s about three-quarters full.
Once the container is ready to go, disposal options vary by location. Many pharmacies, hospitals, fire stations, and health departments accept sharps containers. Some communities offer mail-back programs or special waste pickup services. You can find your local options by calling Safe Needle Disposal at 1-800-643-1643.