You can check your blood sugar at home using a small portable device called a glucose meter (glucometer) and a finger-stick blood sample. The whole process takes about 30 seconds once you have your supplies ready. There are also wearable sensors that track your glucose continuously without finger pricks. Here’s how both methods work, step by step.
What You Need for a Finger-Stick Test
A basic glucose monitoring kit includes four things: the meter itself, disposable test strips designed for that specific meter, a lancing device (a spring-loaded pen that holds a tiny needle), and individually wrapped lancets. You can buy these at any pharmacy without a prescription, though your insurance may cover them if you have diabetes.
Before you start, set up your supplies on a clean, flat surface. Make sure your test strips aren’t expired or damaged, and that they match your meter model. Strips from a different brand or meter won’t give accurate results.
Step-by-Step Finger-Stick Testing
Wash your hands with soap and warm water, then dry them thoroughly. This matters more than you might think. Damp hands can damage the test strip or throw off your reading, and any food residue on your fingers (even trace amounts of fruit juice) can artificially inflate the number.
Load a fresh lancet into the lancing device. Most devices have a dial on the end that controls how deep the needle goes. If you have thicker skin or calluses, you’ll need a deeper setting. Start shallow and adjust from there.
Insert a test strip into the meter’s strip port. Most meters turn on automatically when a strip is inserted. Prick the side of your fingertip rather than the pad. The sides have fewer nerve endings, so it hurts less, and they produce a good-sized blood drop. Gently squeeze your finger until a round drop of blood forms.
Touch the blood drop to the edge of the test strip. The strip will wick the blood in automatically. Don’t smear it or try to add a second drop after the first one is applied. Your meter will display a reading within a few seconds.
Where to Prick Besides Your Fingertip
Some meters allow “alternate site testing” on the forearm or palm. This can be appealing if your fingertips are sore from frequent testing. However, fingertip readings are more accurate, especially when your blood sugar is changing quickly, like right after eating or during exercise. Forearm readings tend to lag behind what’s actually happening in your bloodstream because blood flow is slower there.
Research comparing the two sites found that forearm readings ran about 10 mg/dL lower than fingertip readings when blood sugar was above 200 mg/dL. Palm-of-the-hand testing splits the difference, offering slightly better accuracy than the forearm while still giving your fingertips a break.
How Continuous Glucose Monitors Work
A continuous glucose monitor (CGM) is a small sensor you wear on the back of your upper arm or your abdomen. A tiny filament sits just under the skin and measures glucose in the fluid between your cells, sending readings to your phone or a dedicated receiver every few minutes. You apply the sensor yourself using an applicator that looks like a thick pen. It sticks with adhesive and typically lasts 10 to 14 days before you swap it for a new one.
Once paired with your smartphone, a CGM gives you real-time glucose data without any finger pricks. You can set alarms to alert you when your levels go too high or too low. The sensor needs to stay within about 20 to 33 feet of your phone (depending on the model) to send those notifications. CGMs are prescribed by a healthcare provider and are most commonly used by people with type 1 diabetes or type 2 diabetes on insulin.
How Often to Test
Your testing schedule depends on your type of diabetes and what medications you take.
- Type 1 diabetes: Testing 4 to 10 times a day is typical. Key moments include before meals and snacks, after meals, and before, during, and after exercise. A CGM can replace most of these manual checks.
- Type 2 diabetes on multiple daily insulin injections: Testing before meals and at bedtime is standard, which usually means 3 to 4 times a day.
- Type 2 diabetes on long-acting insulin only: You may only need to test before breakfast and occasionally before dinner or at bedtime.
- Type 2 diabetes managed with diet or non-insulin medication: Routine daily testing may not be necessary, but your provider can advise when periodic checks are helpful.
Test more frequently when you’re sick, starting a new medication, or experiencing symptoms like shakiness, confusion, or unusual thirst. These situations can shift your levels unpredictably.
What Your Numbers Mean
For most adults, a fasting blood sugar (before eating in the morning) between 70 and 100 mg/dL is considered normal. If you have diabetes, your target range is usually 80 to 130 mg/dL before meals and below 180 mg/dL two hours after starting a meal, though your provider may personalize these targets.
A reading below 70 mg/dL is low blood sugar (hypoglycemia). Symptoms include shakiness, sweating, a fast heartbeat, and feeling lightheaded. If you get a reading below 70, treat it quickly with 15 grams of fast-acting carbohydrate, like 4 ounces of juice or 3 to 4 glucose tablets, then recheck in 15 minutes. Severe low blood sugar can cause you to lose consciousness or become unable to eat or drink on your own, requiring emergency treatment with a medication called glucagon.
Consistently high readings above 250 to 300 mg/dL, especially with symptoms like excessive thirst, frequent urination, or nausea, may signal a dangerous spike that needs medical attention.
Common Reasons for Inaccurate Readings
If a reading seems off, the problem is usually one of these fixable issues:
- Expired or improperly stored strips: Heat, humidity, and leaving the strip container open all degrade the chemical coating on the strip. Store them sealed and at room temperature.
- Dirty hands: Traces of lotion, food, or hand sanitizer on your skin will skew results. Soap and water is the gold standard. If you use an alcohol wipe, let your skin dry completely before pricking.
- Too small a blood sample: A generous drop applied once gives the most accurate result. Squeezing too hard to produce blood can also dilute the sample with tissue fluid.
- Extreme temperatures: Both the meter and strips perform best at room temperature. Leaving your kit in a hot car or cold garage can cause errors.
- Old meter or low batteries: Meters should be replaced every 4 to 5 years. Weak batteries can also cause erratic readings.
Safe Disposal of Lancets and Strips
Used lancets are considered medical sharps. Never toss them loose in the trash, where they could prick someone handling the bag. Drop each used lancet into a sharps disposal container immediately after use. You can buy FDA-cleared sharps containers at a pharmacy, or use a sturdy, puncture-resistant plastic container with a screw-on lid (like a laundry detergent bottle).
When the container is about three-quarters full, seal it and dispose of it through your community’s sharps program. Options vary by location but typically include drop-off sites at pharmacies, hospitals, or fire stations, mail-back programs, and special waste pickup services. Your local health department’s website will list what’s available near you.