Checking blood sugar at home takes about 30 seconds using a small device called a glucose meter (glucometer) and a tiny finger prick. The process is straightforward once you’ve done it a few times, and the meter displays your result on screen almost immediately. Here’s exactly how to do it, what your numbers mean, and how to get the most accurate readings.
How to Test With a Glucose Meter
A standard glucose meter kit includes the meter itself, test strips, and a lancing device with small disposable needles. Follow these steps each time you test:
- Wash and dry your hands. Use soap and water, not hand sanitizer. Food residue, lotion, or sugar on your fingers can throw off the reading.
- Insert a test strip into the meter. The meter will turn on and indicate it’s ready.
- Prick the side of your fingertip with the lancet. The side hurts less than the pad because it has fewer nerve endings.
- Touch the edge of the test strip to the blood drop. You need a generous drop, but don’t try to add more blood after the strip has already started absorbing the first one.
- Read your result. The meter displays your blood sugar level in a few seconds.
Some meters allow you to test on your forearm or palm instead of your fingertip. These alternate sites work fine when your blood sugar is stable, but they lag behind fingertip readings when levels are rising or falling quickly, like right after a meal or during exercise. If you get a result from an alternate site that doesn’t feel right, retest with a fingertip sample.
Target Ranges and What Your Numbers Mean
Blood sugar is measured in milligrams per deciliter (mg/dL). The two numbers most people track are their fasting or pre-meal level and their level about two hours after eating. The CDC lists these general targets for most adults with diabetes:
- Before a meal: 80 to 130 mg/dL
- Two hours after starting a meal: less than 180 mg/dL
Normal blood sugar for someone without diabetes generally falls between 70 and 110 mg/dL. Your doctor may set personalized targets that differ from these ranges depending on your age, medications, and overall health.
When Numbers Get Dangerous
Low blood sugar (hypoglycemia) is defined as a reading below 70 mg/dL. Symptoms include shakiness, sweating, confusion, and feeling suddenly weak or dizzy. Eating or drinking something with fast-acting sugar, like juice or glucose tablets, can bring levels back up. If symptoms don’t improve within 10 to 15 minutes, or if the person loses consciousness, that’s a medical emergency.
High blood sugar (hyperglycemia) is defined as a reading above 200 mg/dL. A single high reading after a big meal isn’t necessarily alarming, but sustained levels above 200, especially with symptoms like excessive thirst, frequent urination, or blurred vision, need medical attention. Extremely high readings above 300 mg/dL require urgent action.
When and How Often to Test
Testing frequency depends on your type of diabetes and treatment plan. People using insulin, whether for type 1 or type 2 diabetes, typically test multiple times per day: before meals, before bed, and sometimes before driving or exercise. If you manage type 2 diabetes with oral medications or lifestyle changes alone, you may only need to test once or twice a day, or even less frequently.
The most informative times to check are first thing in the morning (fasting), before meals, and two hours after meals. Testing in pairs, before and after eating, helps you see how specific foods affect your levels. Keep a log of your readings along with notes about what you ate, your activity level, and any unusual stress or illness. Patterns in that log are often more useful than any single number.
Continuous Glucose Monitors
A continuous glucose monitor (CGM) is a small sensor worn on your skin, usually on the back of your upper arm or abdomen, that checks glucose levels automatically every few minutes. Instead of pricking your finger, the sensor reads glucose in the fluid just beneath your skin. These readings closely track blood glucose levels and transmit wirelessly to a phone app or receiver, giving you a real-time graph of your trends throughout the day and night.
CGMs are especially useful for spotting overnight lows, post-meal spikes, and patterns you’d miss with finger sticks alone. They don’t completely replace a glucose meter in every situation. Some CGM systems still require occasional fingertip calibration checks, and a meter remains useful when you suspect the CGM reading is off.
Getting Accurate Readings
Home glucose meters are reliable, but several things can skew results. Knowing what affects accuracy helps you trust your numbers.
Test strip storage matters. Strips are sensitive to heat, moisture, and humidity. Keep them in their sealed container at room temperature, and never use strips that are expired or from a damaged vial. Always make sure the strips match your specific meter model.
Hand preparation is the most common source of error. Wash with soap and water rather than hand sanitizer, and dry completely. If you use an alcohol wipe instead, let the site air-dry before pricking. Even a tiny amount of moisture can dilute the blood sample.
Dehydration and anemia can both make readings less accurate. If you’re sick, vomiting, or have been told you have low red blood cell counts, keep in mind that your meter readings may not perfectly reflect your true blood sugar.
One drop only. Apply a single generous drop of blood to the strip. Adding a second drop after the first one has been absorbed can give a false reading. If the first drop was too small, discard the strip and start fresh.
Safe Lancet Disposal
Used lancets are sharp enough to puncture skin and should never go loose into household trash. Place each used lancet into a sharps disposal container immediately after testing. You can buy FDA-cleared sharps containers at most pharmacies, or use a heavy-duty plastic container with a screw-on lid, like a laundry detergent bottle, as a substitute.
Once the container is about three-quarters full, seal it and dispose of it according to your local guidelines. Options vary by area but commonly include drop-off at pharmacies, hospitals, or fire stations, household hazardous waste collection sites, and mail-back programs. You can find disposal options specific to your location by calling Safe Needle Disposal at 1-800-643-1643. Keep sharps containers out of reach of children and pets, and never reuse them once sealed.