Balancing Blood Glucose (Sugar)

Checking blood glucose levels is the best way to tell how well your child is balancing her insulin, food, and exercise. To make sure your child’s blood glucose level is not too high or too low, your diabetes team will help find a blood glucose target range. For example, a target range for a toddler might be 6 to 12 mmol/L. If your child’s blood glucose level is 8 mmol/L, it is considered normal because it falls inside the range. If it falls above12 mmol/L or below 6 mmol/L, you may need to adjust your child’s insulin or food intake.

Setting the blood glucose target range (type 1)

The blood sugar targets change as your child grows and develops. Target ranges are set by your child’s ability and your own ability to understand diabetes, interpret signs and feelings of low blood sugar levels, and act on them. They are worked out with the diabetes team. Everyone on the team should have the same goals.

Blood glucose target ranges (type 1 diabetes)


Characteristic / ability

Acceptable target range (before meals)

Infants,  toddlers, and preschoolers

  • cannot sense or tell you the signs and symptoms of low blood sugar reaction
  • eating is not predictable

6 to 12 mmol/L
(110 to 220 mg/dL)

School-age children and some young adolescents

  • eating is more predictable (meal plan)
  • can sense and tell you symptoms of low blood sugar reaction
  • somewhat lacking in judgment
  • depends on others to adjust treatment and plan ahead

4 to 10 mmol/L
(70 to 180 mg/dL)

Most adolescents and young adults

  • able to follow a meal plan and eat predictably
  • can recognize and treat low blood sugar reactions
  • understands the concept of balance
  • able to plan ahead

4 to 8 mmol/L
(70 to 145 mg/dL)


For those on insulin pumps, the range may be:

  • before meals: 4 to 7 mmol/L (70 to 125 mg/dL)
  • after meals: below 6 to 9 mmol/L (120 to 160 mg/dL)

When to check blood glucose

For children and teens who get 2 to 4 insulin injections daily, checking blood glucose levels before each meal and before the bedtime snack – 4 times a day – tells you how the insulin is working. One result cannot tell the whole story. Each check gives a unique and important piece of information. For example, here is what each reading tells you:

How to Take a Blood Glucose Test
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  • The pre-breakfast reading tells you how well the dinner or bedtime intermediate-acting insulin worked during the night.
  • The pre-lunch reading tells you how well the rapid-acting and intermediate-acting insulin taken at breakfast is working.
  • Pre-supper readings tell you how well the rapid-acting insulin taken at lunch or the intermediate-acting insulin taken at breakfast is working.
  • The pre-bedtime reading provides information about the rapid-acting insulin taken at supper.

Checking blood sugar before meals has always been encouraged. These readings provide the most useful information for evaluating the effectiveness of insulin doses. It is expected that after-meal blood sugar levels will be higher; this is known as post-prandial hyperglycemia. Nonetheless, recent information suggests that blood sugar levels taken 2 hours after meals may be useful for those on pumps or multiple daily injections with pre-meal rapid-acting insulin and long-acting insulin at night.

Blood Sampler and Lancets
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Glucose testing 4 times a day is ideal but may be a challenge. For example, a lunchtime check for young children in daycare or school ​may be difficult, and staff support will be needed. You will need to negotiate this with the staff at your child’s school. While older school-age children may find lunchtime tests inconvenient, they should be encouraged to do them. 

Once in a while, a check in the middle of the night helps detect those at risk for late-night lows.

Sometimes the blood sugar may be routinely outside the target range (too low or too high). In this case, at least 4 daily checks are needed to determine the correct insulin dose adjustment.

When to do extra blood glucose checks

Glucose Meters
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There are many brands of glucose meters available.

Sometimes blood sugar should be checked apart from the routine. Here are some situations where you should do extra testing:

  • before, during, and after a lot of exercise such as dancing or soccer practice
  • at times of stress
  • if symptoms of low blood sugar are present
  • every 4 hours during an illness
  • at other times prescribed by the diabetes team, or when trying to problem-solve or gather information about the impact of a certain food or activity

Children and teens using insulin pumps need to have more frequent testing to get the most out of their pumps.

It has been said that managing diabetes is a little like performing a complicated juggling act. Sometimes the ball drops. No matter how hard you try, it’s impossible to keep the blood sugar in target range all of the time. Sometimes it will be high, other times low.  Often there is no way of explaining the results. Extremes can result in the following:

  • Hypoglycemia, or low blood sugar, resulting in feeling hungry, shaky, or irritable. This is often referred to as an insulin reaction.
  • Hyperglycemia, or high blood sugar, resulting in urinating and drinking a lot and feeling tired.
  • Diabetic ketoacidosis (DKA)​. This is a life-threatening situation that results from a severe shortage of insulin.

Marcia Frank, RN, MHSc, CDE

Denis Daneman, MB, BCh, FRCPC