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Lows and highs of blood sugar

Recognizing the signs of high and low blood glucose (sugar) is crucial to your health. Managing and controlling your blood sugar level is the best way to stay safe and prevent or delay diabetes related complications

Signs & symptoms of low blood sugar

Keeping blood glucose (sugar) levels in a healthy range can be challenging.

When the amount of sugar in your blood has dropped below your target range (less than 4 mmol/L), it is called low blood sugar (hypoglycemia).

If your blood sugar has dropped, you may feel:

  • shaky, light-headed, nauseated
  • nervous, irritable, anxious
  • confused, unable to concentrate
  • hungry
  • an increase in heart rate
  • sweaty, headachy
  • weak, drowsy
  • numbness or tingling on your tongue or lips

Symptoms of very low blood sugar (less than 2.8 mmol/L) are more severe and can make you:

  • confused and disoriented
  • lose consciousness
  • have a seizure

Make sure you always wear your MedicAlert® identification and talk to your doctor or diabetes educator about prevention and emergency treatment for severe low blood sugar.


Low blood sugar may be caused by:

  • more physical activity than usual
  • not eating on time
  • eating less than you should have
  • taking too much medication
  • drinking alcohol


If you're experiencing the signs of a low blood sugar level, check your blood sugar immediately. Low blood sugar can happen quickly, so it's important to treat it right away. You may need help from another person if your blood sugar is extremely low.

If you don’t have your meter with you, treat the symptoms anyway. It's better to be safe!

First, eat or drink a fast-acting carbohydrate (15 grams)

Good options include:

  • 15 grams of glucose in the form of glucose tablets
  • 15 millilitres (one tablespoon) or three packets of sugar dissolved in water
  • 150 millilitres (⅔ cup) of juice or regular soft drink
  • Six LifeSavers® (one = 2.5 grams of carbohydrate)
  • 15 millilitres (one tablespoon) of honey (do not use for children less than one year old)

Next, wait 15 minutes & re-check your level

If your blood sugar is still low, repeat these steps until your blood sugar is above 4 mmol/L.

If your blood sugar is above 4 mmol/L and your next meal is within an hour, no further action is needed.

If blood sugar is above 4 mmol/L and your next meal is over one hour away—or you will be physically active—eat a snack, such as half of a sandwich or some cheese and crackers (something with 15 grams of carbohydrate and a protein source).

If you need to drive, wait 40 minutes after treating a low blood sugar before getting behind the wheel.

To avoid low blood sugar again, think about why your blood sugar went low and make the necessary changes.

More about managing low blood sugar

If you take insulin or pills that can drop your blood sugar, you need to take steps to prevent or treat low blood sugar, especially when driving.

Signs & symptoms of high blood sugar

High blood sugar (hyperglycemia) occurs when your blood sugar is at or above 11 mmol/L. If you have high blood sugar, you may: 

  • be tired
  • feel thirsty
  • urinate more often than usual, especially during the night


High blood sugar can result when food, activity and medications are not balanced. High blood sugar may happen when you are sick or under stress.


Follow the treatment recommended by your doctor, diabetes educator or other member of your health-care team. If this happens often, you may need to call or see your doctor to:

  • adjust your meal plan
  • adjust your physical activity
  • adjust your medication and/or insulin

More about managing high blood sugar