What is blood sugar?
Blood sugar is the amount of sugar (glucose) in your blood at a given time. This sugar comes from food that we eat that has carbohydrates or from our liver when our sugar lowers during times like sleep or exercise.
Checking your sugar levels
It's important to check your blood sugar level often because it will:
tell you if you have a high or low blood sugar level
show how your lifestyle and medication affect your blood sugar levels
help you and your health-care team make lifestyle, eating and medication changes to improve your blood sugar levels
Checking your blood sugar is an important part of managing your diabetes. How often you check your blood sugar depends on your treatment plan. Talk with your health-care provider about when and how often to check.
There are several ways to check your blood sugar including by finger pricking (capillary testing) or by using glucose sensors (continuous glucose monitors).
Blood sugar monitors (or meters): Blood sugar monitors test the sugar circulating in your blood. You will use something called a lancet to prick your finger so that a blood sample can be put on a test strip that is inserted into the monitor to read your blood sugar. Monitors are available at most pharmacies or from your diabetes educator. Once you receive a monitor, make sure you get the proper training before you begin to use it.
Continuous glucose monitor (CGM): CGM's do not require finger pricks. Instead, a sensor sits on your skin like a small, waterproof patch. It is held in place by sticky material and has a small, thin wire that sits just underneath your skin (usually on the upper arm) to measure sugar levels. The sensor is connected to your smartphone with an app so when you hold your phone over the sensor, it reads and records your sugar levels. You can also get CGMs that connect to insulin pumps and provide blood sugar readings all day and night.
Recommended blood sugar targets*
Blood sugar targets are different for each person and depend on many things. Keeping your blood sugar in your target range helps prevent diabetes complications. Your target may not be the same as the examples in this chart. Ask your health-care provider what your own targets should be.
A1C** | Fasting blood sugar, blood sugar before meals | Blood sugar two hours after eating | |
|---|---|---|---|
Target for most people with diabetes | 7.0% or less | 4.0 to 7.0 mmol/L | 5.0 to 10.0 mmol/L (5.0 to 8.0 mmol/L if A1C targets not met) |
| * This information is based on the Diabetes Canada 2021 update to Chapter 9 of the Clinical Practice Guidelines for the Prevention and Management of Diabetes in Canada and is a guide. **A1C is a measure of your average blood sugar control for the last 2-3 months. It tells you if your blood sugar has been high over time, not just on one day. A1C helps you and your health-care team see how well your diabetes plan is working. NOTE: Fasting blood sugar and blood sugar before meals are different but we group them together here as they share the same blood sugar target range. | |||
What is time in range?
Time in range shows how often your blood sugar is where it should be for you. It’s the percentage of your day your blood sugar stays in your target range. The more time in that range, the better the blood sugar control. For many people, the recommended time in range is to be between 4.0-10.0 mml/L for 70% or more of the day.
Target | Blood sugar | |
|---|---|---|
Time in Range (TIR) | 70% or more | 4.0 – 10.0 mmol/L |
Time Below Range (TBR)* | <4% | 3.9 mmol/L or below |
Time Above Range (TAR) | <25% | >10.0 mmol/L |
| *Time below range means you are having low blood sugar or hypoglycemia NOTE: Individual targets may vary, especially for older adults, children, or those who experience hypoglycemia more often. Talk to your health-care provider about what your targets should be. | ||
Managing your blood sugar when you’re ill
When you are sick, blood sugar can change often and be hard to predict. You want to try to keep your blood sugar in range and not let it go too high or too low.
Check your blood sugar more often, such as every 2–4 hours.
Keep taking your diabetes medications. If you can’t eat or drink, talk to your healthcare provider about your medications.
If using cold or cough medicine, ask your pharmacist for help. Choose sugar‑free cold and cough products when possible.
Stay hydrated by drinking plenty of water or other sugar‑free drinks. Avoid coffee, tea, energy drinks and pop that contains caffeine.
If you are sick and can’t eat, it is VERY IMPORTANT that you:
Drink fluids that contain sugar to provide carbohydrates.
Aim for about 15 grams of carbohydrate from drinks every hour if you’re not eating.
Call your doctor or go to the emergency room if you vomit or have diarrhea two or more times in 4 hours.
If you use insulin, keep taking it when you are sick. Check with your health‑care team about dose or medication changes.