Monitoring glucose levels comes down to two main approaches: finger-prick meters that give you a snapshot reading, and continuous glucose monitors (CGMs) that track your levels around the clock. Which method you need, and how often you should check, depends on your type of diabetes and how you manage it.
Finger-Prick Meters: The Basic Approach
Glucometers are small handheld devices that measure blood sugar from a drop of blood placed on a disposable test strip. They’re inexpensive, widely available at any pharmacy, portable, and deliver results within seconds. The tradeoff is that each test requires a finger prick, and you only get a single number at a single moment. You’re seeing a snapshot, not the full picture of how your glucose moves throughout the day.
Getting an accurate reading takes a little technique. The CDC recommends these steps:
- Wash your hands with soap and warm water, then dry them completely. Residue from food or lotion on your fingers can skew results.
- Massage or shake out your hand to get blood flowing into your fingertip. If your hands are cold, warm them up first, since cold restricts blood flow and makes it harder to get enough blood on the strip.
- Use the lancet to prick the side of your fingertip (less sensitive than the pad).
- Squeeze gently from the base of the finger and touch a small drop of blood to the test strip.
- Record your result along with notes about anything that might have affected it: a recent meal, exercise, stress, or illness.
Rotate which finger you prick each time. Using the same spot repeatedly leads to soreness and calluses that make testing harder over time. Dehydration and anemia can also reduce accuracy, so if you’re sick or not drinking enough water, keep that in mind when interpreting your numbers.
How Often to Test With a Meter
Testing frequency varies widely depending on how you manage your diabetes. If you take multiple insulin injections per day, you’ll often need to test before each meal and at bedtime. If you use an intermediate or long-acting insulin, testing before breakfast and sometimes before dinner or at bedtime may be enough.
If you manage type 2 diabetes with non-insulin medications, or with diet and exercise alone, you may not need to test every day. Your doctor will help you figure out a schedule based on how stable your levels tend to be and what information is most useful for adjusting your plan.
Continuous Glucose Monitors
A CGM uses a small sensor, roughly the size of a quarter, applied to the back of your arm or your belly. A tiny flexible catheter sits just under the skin and measures glucose in the fluid between your cells (called interstitial fluid). The sensor takes automatic readings every few minutes, day and night, and sends the data to your phone or a dedicated receiver.
The biggest advantage over a meter is the continuous data stream. Instead of isolated snapshots, you see curves and trends. A CGM shows you how a specific meal spiked your glucose, how exercise brought it down, and what happened overnight while you slept. It can also send alerts when your levels are dropping or rising fast, which is especially valuable for people at risk of dangerous lows.
CGMs do cost more than meters, and the sensors need to be replaced every couple of weeks. Some people also need time to get used to wearing a device on their body. But for anyone on insulin, a CGM dramatically reduces the number of finger pricks needed and provides information that finger-prick testing simply cannot.
The Lag Time to Know About
One thing to understand about CGMs: they measure glucose in the fluid around your cells, not directly in your blood. That fluid lags behind your bloodstream, so CGM readings can trail a finger-prick reading by up to 15 minutes, though the delay is typically shorter. This matters most when your glucose is changing rapidly, like right after a meal or during intense exercise. If your CGM shows a number that doesn’t match how you feel, a confirmatory finger prick can help.
Time in Range: The Key CGM Metric
If you use a CGM, the most important number to pay attention to isn’t any single reading. It’s your “time in range,” which measures what percentage of your day you spend between 70 and 180 mg/dL. The American Diabetes Association recommends aiming for at least 70% of readings in that window, which works out to roughly 17 out of every 24 hours.
Time in range gives you a much richer picture than any single blood sugar check. Two people can have the same average glucose, but one might achieve it by staying steady between 100 and 150 all day, while the other swings from 50 to 250. Their averages match, but their experiences and health risks are very different. Time in range captures that difference.
HbA1c: The Long-Term View
Your HbA1c (sometimes just called A1c) is a blood test done at your doctor’s office, typically every three to six months. It reflects your average blood sugar over the previous two to three months by measuring how much glucose has attached to your red blood cells. It’s the standard benchmark for overall glucose management.
The relationship between A1c and daily glucose numbers is straightforward. An A1c of 6% corresponds to an average glucose of about 126 mg/dL. Each percentage point above that adds roughly 29 mg/dL to the average: 7% equals about 154 mg/dL, 8% equals about 183, and 9% equals about 212. Knowing this conversion helps you connect your daily readings to the number your doctor discusses at checkups.
A1c is useful but has a blind spot. Like average glucose, it can’t tell you whether your levels were stable or swinging wildly. That’s why daily monitoring, whether by meter or CGM, pairs with A1c to give you the complete picture.
Making Sense of Overnight Patterns
If you notice high glucose when you wake up, two different things could be causing it. The dawn phenomenon is a natural rise in blood sugar that happens in the early morning hours, driven by hormones that prepare your body to wake up. The Somogyi effect is a rebound high caused by your blood sugar dropping too low during the night, which triggers your liver to release stored glucose.
The distinction matters because the fixes are opposite. To tell them apart, check your glucose between 3 a.m. and 5 a.m. for several nights. If that reading is normal or high, you’re experiencing the dawn phenomenon. If it’s low, the Somogyi effect is more likely, and your evening medication or insulin dose may need adjustment. A CGM makes this much easier since it captures overnight data automatically without setting an alarm.
Needle-Free Monitoring
A new category of glucose monitor is beginning to reach the market. In September 2025, the FDA granted clearance to Biolinq Shine, the first wearable glucose sensor that doesn’t require a needle for placement. Instead of a traditional filament inserted under the skin, it uses a microsensor array that sits up to 20 times more shallow than conventional CGM sensors. The patch goes on your forearm and displays real-time glucose feedback through a color-coded LED light, while also syncing activity and sleep data.
It was initially developed for people with type 2 diabetes who don’t use insulin. Whether needle-free monitors will eventually work well enough for insulin dosing decisions remains to be seen, but for people who’ve avoided monitoring because of the needle, this removes a significant barrier.