High blood sugar, also called hyperglycemia, happens when there is not enough insulin in the body to help move glucose from the bloodstream into cells. This is particularly important in type 1 diabetes, where the body produces little to no insulin. Without sufficient insulin, glucose cannot move into cells and instead builds up in the bloodstream. This is why people with type 1 diabetes need insulin every day to help manage blood sugar levels. If left untreated, high blood sugar can lead to serious complications.
Highlights:
- Since high blood sugar can occur without symptoms, monitor regularly to catch it early.
- Learn how to manage high blood sugar levels.
- Illness, stress and missed insulin are common triggers of hyperglycemia.
- Learn when to check for ketones to prevent diabetic ketoacidosis.
- Regular monitoring helps you stay in range and avoid long-term damage.
What are the symptoms of high blood sugar?
Blood sugar readings of ≥11 mmol/L are considered high. Common symptoms include:
- Frequent urination (especially overnight)
- Excessive thirst
- Fatigue
- Blurred vision
- Headaches
Some people may not notice symptoms, even when blood sugar is high. This makes regular monitoring especially important.
What causes high blood sugar?
There are many reasons why your blood sugar may rise, including:
- Not taking enough insulin for the carbohydrates you eat
- Eating more than planned
- Reduced physical activity
- Illness or infection (especially if vomiting)
- Emotional stress
- Skipping insulin doses
- Problems with insulin administration, such as a broken insulin pump or insulin left out on a hot summer day for too long
Have you been noticing that your morning blood glucose readings have been high for no reason? This may be due to something called “the dawn phenomenon.” Click here to learn more about it.
How do you treat high blood sugar?
If your blood sugar is high, you can try the following steps:
- Take correction insulin
- Follow your prescribed correction dose.
- Do not take too much insulin because you can risk low blood sugar or Read more on treating hypoglycemia
- Stay hydrated
- High blood sugar can cause dehydration. Drink plenty of water to replace fluids lost through increased urination.
- Identify the cause
- Consider recent food intake, missed insulin, illness or stress.
- Look for patterns in your blood sugar to help guide adjustments.
- Check for ketones
- If your blood sugar is ≥14 mmol/L or if you are feeling unwell, it could be ketones.
- If ketones are present, avoid exercise.
- Seek medical attention if:
- Blood sugar remains high despite corrective treatment
- Ketones are present
- You are experiencing nausea, vomiting or difficulty breathing
Talk to your doctor, diabetes educator or another member of your healthcare team.
Recommended targets for most people with diabetes are:
- A1C: ≤7.0%
- Fasting blood glucose: 4.0-7.0 mmol/L
- 2 hours after eating: 5.0-10.0 mmol/L
Your targets may differ from the values above, so follow the target values set by your doctor or diabetes care team.
Why is it important to treat high blood sugar?
Over time, high blood sugar can lead to complications affecting the heart, eyes, nerves and kidneys.
Diabetic ketoacidosis (DKA) is a serious complication of prolonged high blood sugar. When there is not enough insulin, the body breaks down fat for energy instead of sugar, producing toxic chemicals called ketones. High ketone levels can be dangerous and may lead to coma or death if not treated.
Some key signs and symptoms of DKA include:
- High blood sugars (≥14 mmol/L)
- Thirst, dry mouth and tiredness (similar to symptoms of hyperglycemia)
- Rapid breathing or shortness of breath
- A “fruity” breath
- Nausea, vomiting, abdominal pain
- Weakness, confusion, loss of consciousness (coma)
Ketones can be detected using a blood ketone meter or urine ketone strips available for purchase at pharmacies. Monitoring blood ketones is recommended as it is more accurate than measuring urine ketones. Talk to your pharmacist for more information.
Early signs of DKA may sometimes be managed at home with the guidance of your healthcare team. However, if your blood sugar remains high, symptoms are worsening and ketones are above 3.0, go to the hospital.
How do you prevent high blood sugar?
You can reduce the risk of high blood sugar by:
- Taking insulin as prescribed
- Monitoring blood sugar regularly
- Matching insulin to your carbohydrate intake
- Staying active
- Managing stress and illness
- Checking insulin storage and expiration
Your 3-step action plan to balance blood sugars
- Check now: Check your blood glucose and look for possible causes of variations, such as missed insulin, food, illness, or stress.
- Correct today: Take insulin and hydrate. You’ll start lowering blood sugar levels.
- Protect yourself: Check for ketones if blood sugar is ≥14 mmol/L. You’ll reduce your risk of DKA.
Managing high blood sugar is an important part of living with type 1 diabetes. By monitoring regularly, recognizing patterns and acting early, you can stay in optimal blood sugar range and reduce the risk of serious complications.
