You can check your glucose levels at home with a handheld blood glucose meter (a finger prick test) or a continuous glucose monitor worn on your body. Clinical settings offer additional tests, including fasting blood draws and the A1C test, which measures your average blood sugar over roughly three months. The method that’s right for you depends on whether you’re managing a diagnosis, screening for one, or simply curious about your numbers.
Using a Blood Glucose Meter
A handheld glucose meter is the most common way to check blood sugar at home. The process takes under a minute once you get the hang of it. Here’s how it works:
- Make sure the meter is charged and ready to use.
- Wash your hands with soap and warm water, then dry them thoroughly.
- Massage or shake your hand to encourage blood flow into your fingertip.
- Use a lancet (a small spring-loaded needle) to prick the side of your finger.
- Squeeze gently from the base of the finger to form a small drop of blood.
- Touch the test strip to the blood drop so it absorbs the sample.
- Insert the strip into the meter (some meters require the strip to be inserted first).
- Read your result after a few seconds and record it.
Never share lancets or testing equipment with anyone, even family members. Dispose of used lancets and strips in a proper container.
Getting Accurate Readings
Hand washing matters more than you might think. Food residue on your fingers, especially from fruit or sugary snacks, can artificially raise your reading. Soap and warm water is the recommended method. If you use an alcohol swab instead, wait at least 30 seconds for it to fully evaporate before pricking your finger. Testing while the skin is still wet from alcohol can lower your result because the disinfectant dilutes the tiny blood sample (often just 0.6 microliters) that the strip absorbs. Thinner lancets are more sensitive to this effect.
Some meters allow testing from the upper arm, forearm, base of the thumb, or thigh. These alternate sites work well when blood sugar is stable, but they lag behind fingertip readings when glucose is changing rapidly, such as after a meal, after taking insulin, or during exercise. If you suspect low blood sugar or your symptoms don’t match the alternate-site result, switch to a fingertip test.
When and How Often to Test
Testing frequency depends on your type of diabetes and whether you take insulin. The most useful times to check are:
- First thing in the morning, before eating or drinking (your fasting level)
- Before meals
- Two hours after a meal (to see how food affected your blood sugar)
- At bedtime
If you have type 1 diabetes, take insulin for type 2, or frequently experience low blood sugar, your care team may ask you to test more often, including before and after physical activity. Logging your results alongside notes about meals, stress, or exercise helps reveal patterns that a single number can’t show.
Target Ranges for People With Diabetes
The American Diabetes Association recommends these targets for most nonpregnant adults with diabetes: 80 to 130 mg/dL before a meal, and less than 180 mg/dL one to two hours after starting a meal. Your personal targets may differ based on your age, how long you’ve had diabetes, and other health conditions, so these numbers are a starting point rather than a universal rule.
Continuous Glucose Monitors
A continuous glucose monitor, or CGM, tracks your levels around the clock without repeated finger pricks. It uses a tiny sensor inserted just under the skin, typically on your belly or the back of your upper arm, held in place by an adhesive patch. The sensor measures glucose in the fluid between your cells (called interstitial fluid), which closely mirrors blood glucose levels. Readings transmit wirelessly to a receiver, smartphone app, or insulin pump.
Disposable sensors are the most common type and are replaced every 7 to 14 days depending on the brand. Implantable sensors, placed by a healthcare provider, last longer. CGMs are especially useful for spotting overnight lows, post-meal spikes, and trends that periodic finger pricks would miss. Most still recommend an occasional finger-prick confirmation if a reading doesn’t match how you feel.
Lab Tests Your Doctor May Order
Home meters give you a snapshot, but clinical tests are used to diagnose diabetes and prediabetes. Three tests are standard.
Fasting Blood Sugar Test
You fast for at least eight hours (usually overnight), then have blood drawn. A result of 99 mg/dL or below is normal. Between 100 and 125 mg/dL falls in the prediabetes range. A reading of 126 mg/dL or higher on two separate tests indicates diabetes.
A1C Test
The A1C measures the percentage of your red blood cells that have sugar attached to them, reflecting your average blood sugar over roughly two to three months. No fasting is required. Below 5.7% is normal, 5.7% to 6.4% signals prediabetes, and 6.5% or higher points to diabetes. Because it captures a long-term average, a single high-stress day or missed meal won’t skew the result.
Oral Glucose Tolerance Test
This test is more involved. After fasting for eight hours, you drink a solution containing 75 grams of sugar, then have your blood drawn at the one-hour and two-hour marks. At two hours, a level below 140 mg/dL is normal. Between 140 and 199 mg/dL suggests prediabetes. A reading of 200 mg/dL or higher suggests diabetes. This test is also used to screen for gestational diabetes, though the diagnostic cutoffs are different: a fasting level of 92 mg/dL or higher, a one-hour reading of 180 mg/dL or higher, or a two-hour reading of 153 mg/dL or higher.
A random blood sugar test, taken at any time regardless of when you last ate, can also flag diabetes if the result is 200 mg/dL or higher, though it’s typically used when symptoms are already present rather than as a routine screen.
Non-Invasive Devices and Smartwatches
Several companies market watches and wearable sensors that claim to measure glucose without a needle. As of 2024, no non-invasive glucose monitoring device has received FDA approval for managing diabetes. The FDA issued a safety warning that year cautioning that these devices could pose a risk to people with diabetes who rely on them for treatment decisions. They can be purchased without a prescription, which adds to the confusion. At best, they may detect general trends, but they are not reliable enough for real-time decisions like adjusting insulin doses. If accurate glucose data matters for your health, stick with a meter or CGM that has regulatory clearance.