You can test your blood sugar at home with a small portable device called a glucose meter, which gives a reading in seconds from a single drop of blood. For a fuller picture, doctors use lab tests like the A1C, fasting glucose, and oral glucose tolerance test to diagnose diabetes or track how well it’s being managed. The method that’s right for you depends on whether you’re monitoring a known condition or checking for the first time.
Testing at Home With a Glucose Meter
A blood glucose meter (also called a glucometer) is the most common way people check their sugar levels day to day. The device reads a small blood sample placed on a disposable test strip and displays your blood sugar in milligrams per deciliter (mg/dL) within a few seconds. Here’s the process recommended by the CDC:
- Prepare. Make sure your meter is charged and ready. Wash your hands with soap and warm water, then dry them well. Residue from food or lotion on your fingers can throw off a reading.
- Get blood flowing. Massage or shake out your hand to bring blood into your fingertip.
- Prick your finger. Use a lancet (a small spring-loaded needle) on the side of your fingertip, which tends to be less painful than the pad.
- Apply the sample. Squeeze gently from the base of the finger and touch the blood drop to the test strip.
- Read and record. Insert the strip into the meter if you haven’t already. Your reading appears in a few seconds. Log it in an app, notebook, or your meter’s memory.
- Dispose safely. Drop the used lancet and strip into a trash container. Never share lancets with anyone, even family members.
Most people test on their fingertips because the blood there reflects current glucose levels more accurately than other sites. Some meters allow testing on the forearm or palm, but those readings can lag behind fingertip readings when blood sugar is changing quickly, such as after a meal or during exercise.
When and How Often to Test
The best times to check depend on the type of diabetes you have and how you’re treating it. The general pattern is to test at moments when your blood sugar is most likely to shift: before eating, after eating, around exercise, and at bedtime.
If you have type 1 diabetes, the Mayo Clinic notes that testing 4 to 10 times a day is common. That typically means before meals and snacks, after meals, before and after exercise, at bedtime, and sometimes during the night. You’ll also want to test more frequently when you’re sick, adjusting medications, or changing your routine.
For type 2 diabetes managed with multiple daily insulin injections, testing before meals and at bedtime is standard. If you use a longer-acting insulin, you may only need to test before breakfast and occasionally before dinner. People managing type 2 with diet and oral medication alone often test less frequently, guided by their care team.
The American Diabetes Association recommends aiming for 80 to 130 mg/dL before meals and less than 180 mg/dL two hours after a meal. These are general targets; yours may differ based on age, how long you’ve had diabetes, and other health factors.
Continuous Glucose Monitors
A continuous glucose monitor, or CGM, is a small sensor worn on the skin (usually the arm or abdomen) that automatically checks your glucose every 5 to 15 minutes, day and night, without finger sticks. A tiny wire sits just beneath the skin and measures glucose in the fluid between your cells. You apply it with a one-press inserter; a small needle places the wire, then retracts immediately.
The biggest advantage over a standard meter is context. A finger stick tells you what your blood sugar is right now. A CGM shows you what it is, which direction it’s heading, and how fast it’s moving. You see real-time graphs and trend arrows on your phone or a receiver, which makes it much easier to catch a rising or falling pattern before it becomes a problem.
There are two main types. A “flash” CGM sends data to your device only when you scan the sensor. A real-time CGM streams data continuously and can alert you with alarms when glucose goes too high or too low. Both types let you share data with your doctor. For people with type 1 diabetes or anyone on insulin who experiences unpredictable swings, a CGM can be a significant upgrade over finger-stick testing alone.
Lab Tests Your Doctor May Order
Home meters give you snapshots. Lab tests give your doctor the bigger diagnostic picture. Three tests are standard.
A1C Test
The A1C measures your average blood sugar over the previous three months. It works by looking at how much glucose has attached to your red blood cells over their lifespan. No fasting is required. An A1C of 6% translates to an estimated average glucose of about 126 mg/dL, while 7% corresponds to roughly 154 mg/dL and 8% to about 183 mg/dL. Most people with diabetes aim for an A1C below 7%, though individual targets vary. This test is typically repeated every three to six months.
Fasting Plasma Glucose Test
This measures your blood sugar at a single point after you’ve had nothing to eat or drink (except water) for at least 8 hours. It’s usually done first thing in the morning. It’s straightforward, inexpensive, and one of the most common screening tools for diabetes and prediabetes.
Oral Glucose Tolerance Test
The OGTT also requires an overnight fast. A blood sample is taken first, then you drink a sugary liquid. Your blood is drawn again two hours later to see how effectively your body processed the sugar. It’s more involved and more expensive than a fasting test, but it can catch problems that a fasting test might miss. Pregnant women often undergo a version of this test with blood drawn every hour for two to three hours to screen for gestational diabetes.
Urine Glucose Tests
Older screening methods checked for sugar in urine, and you may still encounter urine glucose strips. They work on a simple principle: your kidneys normally hold onto glucose and send it back into your bloodstream, so healthy urine contains little to no sugar. When blood sugar climbs high enough, the kidneys can’t keep up, and glucose spills into the urine.
The problem is that by the time sugar shows up in urine, blood sugar is already quite elevated, so the test misses moderate highs entirely. Blood testing is far more accurate and has largely replaced urine testing for diabetes screening and monitoring. Urine tests are still used occasionally when blood draws are difficult, such as in people with scarred veins, or when a doctor suspects a rare kidney condition.
What the Numbers Mean
Blood sugar readings matter most when you understand the ranges. The American Diabetes Association defines low blood sugar (hypoglycemia) as anything below 70 mg/dL. At that level you may feel shaky, sweaty, confused, or unusually hungry. Severe highs (hyperglycemia) start at 250 mg/dL and above, which can cause extreme thirst, frequent urination, blurred vision, and fatigue. Both extremes require prompt attention.
Between those boundaries, context matters. A fasting reading of 95 mg/dL is normal. A reading of 160 mg/dL an hour after a large meal may be perfectly expected for someone with diabetes who is otherwise well-controlled. Tracking patterns over days and weeks is more useful than reacting to any single number.
Getting Accurate Readings
A glucose meter is only as reliable as the conditions you use it in. A few common factors can skew results:
- Expired or damaged test strips. Check the expiration date on every vial. Strips that have been exposed to moisture or left out of their sealed container can give false readings.
- Temperature. Store your meter and strips at room temperature. Extreme heat or cold affects the chemistry of the strip and the electronics of the meter.
- Dirty hands. Even a trace of fruit juice or sugar on your fingertip can inflate a reading. Washing and drying thoroughly is the single easiest way to improve accuracy.
- Dehydration or anemia. The concentration of red blood cells in your blood affects how meters calculate glucose. If you’re dehydrated or have low red blood cell counts, readings can be less reliable.
Most meters also come with a control solution you can use to verify the device is working properly. Running a control test once a week, or whenever you open a new vial of strips, is a good habit. If your readings consistently don’t match how you feel, bring your meter to your next appointment so your care team can compare it against a lab draw taken at the same time.