You can measure glucose levels at home with a fingerstick blood glucose meter, a continuous glucose monitor (CGM) worn on your body, or through lab tests ordered by a healthcare provider. Each method serves a different purpose: fingerstick meters give you a snapshot reading in seconds, CGMs track your levels around the clock, and lab tests like the A1C reveal your average blood sugar over the past two to three months.
Fingerstick Blood Glucose Meters
A fingerstick meter is the most common way to check glucose at home. The process takes about 30 seconds once you get the hang of it. You prick the side of a fingertip with a small spring-loaded device called a lancet, touch the blood drop to a disposable test strip, and the meter displays your reading.
Start by washing your hands with soap and water and drying them thoroughly. Damp fingers can damage the test strip or throw off your reading. Set out your supplies in order: lancing device, a fresh lancet, your meter, and a test strip. When you pull a strip from its container, close the container right away to keep moisture out.
For the lancet device, set the puncture depth to level 1 or 2. You can increase it later if you don’t get a large enough blood drop. Prick the side of your fingertip rather than the center or pad, which are more sensitive and tend to hurt more. Use a different spot each time to avoid building up sore areas. You have 20 possible sites across all ten fingers (both sides of each fingertip), so rotating is easy.
After you press the lancet’s release button, look for a blood drop. If it’s too small, gently massage or squeeze your finger, but don’t press hard. If you still can’t get enough blood, increase the depth setting by one level and try again on the same finger. Touch a generous drop to the test strip in one motion. Adding blood after the first application can give inaccurate results.
What Can Throw Off a Meter Reading
Home glucose meters are held to an international accuracy standard: at least 95% of readings must fall within 15% of the true value (or within 15 mg/dL for lower glucose levels). That’s reasonably precise, but several things can push a reading outside that range.
Residue on your skin is the most common culprit. Traces of food, lotion, or dirt on your fingertip can artificially raise or lower the number. Soap and water are the best prep. Hand sanitizer is not a reliable substitute, and if you use an alcohol wipe, let the site dry completely before pricking. Dehydration and anemia (low red blood cell count) also reduce accuracy. Extreme temperatures affect both the meter and the strips, so store them at room temperature and avoid leaving your kit in a hot car or cold garage. Always check the expiration date on your test strips, and keep them sealed in their original container.
Continuous Glucose Monitors
A CGM is a small sensor, roughly the size of two stacked coins, that sits just under your skin and measures glucose every few minutes. Unlike a fingerstick meter, it doesn’t sample blood directly. Instead, it reads glucose in the thin layer of fluid between your cells, called interstitial fluid. This means CGM readings lag a few minutes behind blood readings, especially when your glucose is rising or falling fast.
You apply the sensor yourself using an applicator that inserts a tiny filament under the skin, typically on the back of your upper arm or your abdomen. Most sensors last 7 to 15 days depending on the brand, at which point you peel it off and apply a new one. An implantable version, placed by a clinician, can last several months.
CGMs send data to a smartphone app or a dedicated receiver, giving you a continuous line graph of your glucose throughout the day and night. This is especially useful for spotting patterns: how your levels respond to meals, exercise, stress, or sleep. For people with diabetes using CGMs, spending more than 70% of the day within their target range is a widely used benchmark for good glucose management.
Lab Tests for Long-Term Glucose
Home meters and CGMs tell you what your glucose is doing right now. Lab tests fill in the bigger picture.
The A1C test measures the percentage of your red blood cells that have glucose attached to them. Because red blood cells live about three months, the A1C reflects your average blood sugar over that window. It requires a simple blood draw and no fasting. The diagnostic thresholds are straightforward:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
For people already managing diabetes, the American Diabetes Association recommends an A1C below 7% for most nonpregnant adults. Some people with otherwise good health and low risk of dangerous blood sugar drops may aim lower, around 6.5%. Others with complex health situations may have a more relaxed target.
Oral Glucose Tolerance Test
The oral glucose tolerance test (OGTT) checks how efficiently your body processes a large sugar load. You fast for at least eight hours, then drink a solution containing 75 grams of glucose. Your blood is drawn one hour and two hours later. This test is commonly used to diagnose gestational diabetes during pregnancy, sometimes with a larger 100-gram solution and blood draws at one, two, and three hours. It takes longer than a standard blood draw, but it reveals how your body handles sugar in real time rather than just measuring a fasting snapshot.
Understanding Your Numbers
Glucose is measured in milligrams per deciliter (mg/dL) in the United States and in millimoles per liter (mmol/L) in most other countries. To convert between them, divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18 to get mg/dL. A fasting reading of 100 mg/dL, for example, equals about 5.6 mmol/L.
For most nonpregnant adults with diabetes, recommended targets are a fasting (pre-meal) glucose of 80 to 130 mg/dL and a post-meal peak below 180 mg/dL. People without diabetes typically run lower, with fasting levels below 100 mg/dL and post-meal readings that rarely exceed 140 mg/dL.
Context matters when reading your numbers. A single high or low reading doesn’t define your health. Trends over days and weeks, especially when captured by a CGM or tracked in a log, are far more informative than any individual measurement. If you’re testing with a fingerstick meter, recording your results alongside what you ate, when you exercised, and how you felt helps you and your provider spot meaningful patterns rather than reacting to isolated spikes or dips.
Choosing the Right Method
The best way to measure glucose depends on why you’re checking. If you take insulin and need to make dose decisions throughout the day, a CGM offers the most useful real-time data. If you’re monitoring type 2 diabetes managed with oral medication or lifestyle changes, periodic fingerstick checks (often first thing in the morning and after meals) may be enough. If you don’t have diabetes but want to know where you stand, an A1C or fasting glucose test through your provider gives you a clear baseline without any home equipment.
Cost and insurance coverage also play a role. Fingerstick meters are inexpensive, often under $30, but test strips add up over time. CGMs carry a higher upfront cost and typically require a prescription, though coverage has expanded significantly in recent years. Lab tests are usually covered as part of routine preventive care.