High blood sugar: What it is, and what to do

High blood sugar (or hyperglycemia) occurs when a student’s blood sugar is higher than the target range. Target ranges are specific to each student, based on Diabetes Canada’s Clinical Practice Guidelines. The student’s target range can be found in their diabetes care plan.

High blood sugar is usually caused by:

  • extra food, without extra insulin,
  • not enough insulin,
  • decreased physical activity,
  • an issue with their insulin pump, or
  • stress or excitement.

Sometimes the cause of high blood sugar isn't obvious. Remember that high blood sugar is treated with insulin. Never suggest a student use physical activity to try to lower blood sugar.

All students with type 1 diabetes have high blood sugar from time to time. Students with high blood sugar may have difficulty concentrating in class, but usually, it is not an immediate cause for concern at school.

However, when a student with diabetes has very high blood sugar (as defined in the student's care plan) and is feeling unwell, immediate action is required.

High blood sugar can occur when there is not enough insulin—and when this happens, the body produces chemicals called ketones. When a person with diabetes has very high blood sugar over a period of time, they have to check for ketones (which is done either by using a urine strip or with a drop of blood and a ketone meter/strips).


Ketones can make a person with diabetes feel sick and can lead to serious illness. They also cause fruity-smelling breath, which is an obvious sign that the student is unwell. A student’s diabetes care plan will include details on whether and/or how to check for ketones at school.

Symptoms of high blood sugarSymptoms that need immediate action
  • Extreme thirst
  • Frequent urination
  • Headache
  • Hunger
  • Abdominal pain
  • Blurry vision
  • Warm, flushed skin
  • Irritability
  • Rapid, deep breathing
  • Vomiting
  • Fruity breath

What to do when a student has high blood sugar

Step 1: Check blood sugar to confirm blood sugar is higher than the target range. Even students who are independent may need help with this task if they are unwell.

Step 2: Depends on whether the student is feeling well or unwell. See appropriate responses for each scenario below.

If the student is unwell

Contact parents immediately if a student is unwell, has severe abdominal pain or nausea, or symptoms of very high blood sugar such as rapid, deep breathing, vomiting and/or fruity breath.

If the student is well

If the student is well, follow instructions for high blood sugar in their care plan. Allow unlimited trips to the washroom, and encourage them to drink plenty of wate


If you see these symptoms in a child without type 1 diabetes, speak to their parents/caregivers and suggest they see a doctor. It may be a sign that they have undiagnosed diabetes.

REMEMBER: Although high blood sugar is usually not cause for concern, very high blood sugar with ketones or vomiting is an emergency. Call parents/caregivers to pick up a student immediately if they are unwell or have symptoms of very high blood sugar. If the student is feeling well, follow instructions in their diabetes care plan and allow them to drink plenty of water and use the washroom as needed.

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