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Assigning A Value To Blood Glucose Numbers

When it comes to diabetes, you’re constantly told to monitor your blood glucose closely. But what exactly are you supposed to be monitoring—and why?

Good diabetes management involves knowing target values, which are the numbers where the blood glucose level is said to be normal.

  • Fasting or preprandial (pre-meal) blood glucose: between 4.0 and 7.0 mmol/L
  • Postprandial blood glucose (two hours after a meal): between 5.0 and 10.0 mmol/L

Anything below these values is considered to be hypoglycemia; the reverse is hyperglycemia. Both involve health risks.

Note that the amount of glucose per litre of blood is expressed in millimoles per litre (mmol/L). (It’s important not to confuse these numbers with values measured in milligrams per decilitre [mg/dL], which are mostly used in the United States.)

As for A1C levels (a.k.a. HbA1c, or glycated hemoglobin—average blood glucose levels for the last two to three months), which are obtained from a blood test, they should be 7% or less. A value greater than this points to risks of long-term complications.

Your own target values

Based on factors such as your age, your health (including the presence or absence of cardiovascular disease), or how long you’ve had diabetes, for example, your physician can set target values specifically for you that are slightly different from those listed above. Similarly, target values will differ if you’re pregnant.

Keeping a (more or less private) diary

Blood sugar levels vary daily depending on food intake and physical activities, but also on factors such as stress—whether psychological or physical (injury or illness)—alcohol intake, and so on.

As a result, it is strongly recommended that you keep a diary (paper or electronic) that includes not only the results of your tests, but also your meals, snacks and physical activities, in addition to measurements such as your weight or blood pressure. Also consider writing down what’s going on in your life and what you’re worried about. That can also help you understand your blood sugar fluctuations.

Being diligent

When should you test your blood glucose? Often enough to be able to determine how different elements affect it, and regularly enough to see if this influence is constant.

If you are insulin-dependent, you should do this when you wake up (while you’re fasting), before meals, before each injection and before going to sleep. Of course, your health care provider can help you determine how often you should be testing your blood glucose.

If you have a cold or are feeling stressed, for example, you should be testing your blood glucose a bit more often: these stressors can affect it to some degree.

Going for a healthy lifestyle

Ideally, you would not only avoid major deviations (hypoglycemia and hyperglycemia can both cause damage) but also learn to identify and predict the effects of various factors on your blood glucose levels.

With all this information in hand, you’ll be better able to adapt certain elements of your lifestyle and, with the help of a health care professional, adjust your medication.

Careful monitoring of your blood glucose will also help you spot anomalies early and avoid any problems that they may cause. Knowing your target values is of course fundamental, but so is knowing what to do when you stray from them. Talk to your health care professional about this.


Beyond all the numbers, keep in mind that the whole point of this approach is to get to know yourself better and maintain a good quality of life for a long time.

American Diabetes Association, “Checking Your Blood Glucose”: Accessed February 8, 2017.
Canadian Diabetes Association, “Managing your blood glucose”: Accessed February 8, 2017.
Canadian Diabetes Association, “Managing your blood sugar”: Accessed February 8, 2017.
Diabetes Canada, “Targets for Glycemic Control”: Accessed February 17, 2017.
Diabetes Québec, “Self-Monitoring of Blood Glucose”: Accessed February 8, 2017.
Diabetes Québec, “Target blood glucose levels”: Accessed February 8, 2017.
Fédération Française des Diabétiques, “L’HbA1c ou hémoglobine glyquée”: Accessed January 27, 2017.
Roche Diagnostics Belgium, “Contrôler soi-même sa glycémie : simple comme bonjour!”: Accessed February 10, 2017.
WebMD, “Blood Glucose”: Accessed February 8, 2017.
Sé, “Comment interpréter les données du glucomètre”: Accessed February 8, 2017.

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