Content Map Terms

Diabetes-Related High and Low Blood Sugar Levels

British Columbia Specific Information

​Diabetes is a condition where your body is not able to regulate levels of glucose (sugar) in your blood. This results in too much or too little sugar in your blood. There are 3 types of diabetes: type 1, type 2 and gestational diabetes.

Type 1 diabetes occurs when your pancreas stops producing insulin. If you have type 1 diabetes, you will need to use an insulin injector to make sure your body gets enough insulin. For more information about type 1 diabetes, visit the Diabetes Canada Living with Type 1 Diabetes web page.

Type 2 diabetes occurs when your body does not respond properly to the insulin it produces. Treatment includes medication and lifestyle changes to your diet and exercise routine. To learn more about how healthy eating can help you manage your blood sugar, see our Healthy Eating Diabetes and Hypoglycemia web page. For more information about diabetes, visit the Diabetes Canada Living with Type 2 Diabetes web page.

Gestational diabetes may occur during pregnancy if your level of blood glucose becomes too high. This may cause problems for you and your baby. Controlling blood sugar levels with treatment and a healthy lifestyle will minimize the risks. For information about diabetic screening when pregnant, visit BC Women’s Hospital Diabetes and Pregnancy web page.

For further information on the prevention, management and diagnosis of diabetes, speak to your health care provider. You may also call 8-1-1 to speak to a registered dietitian, registered nurse or pharmacist. Our dietitians are available Monday to Friday 9:00 a.m. to 5:00 p.m. Our nurses are available anytime, every day of the year. Our pharmacists are available every night from 5:00 p.m. to 9:00 a.m. You can also Email a HealthLinkBC Dietitian.

Topic Overview

Diabetes-related blood sugar levels

When you have diabetes, you may have high blood sugar levels (hyperglycemia) or low blood sugar levels (hypoglycemia) from time to time. A cold, the flu, or other sudden illness can cause high blood sugar levels. You will learn to recognize the symptoms and distinguish between high and low blood sugar levels. Insulin and some types of diabetes medicines can cause low blood sugar levels.

Learn how to recognize and manage high and low blood sugar levels to help you avoid levels that can lead to medical emergencies, such as diabetic ketoacidosis or dehydration from high blood sugar levels or loss of consciousness from severe low blood sugar levels. Most high or low blood sugar problems can be managed at home by following your doctor's instructions.

You can help avoid blood sugar problems by following your doctor's instructions on the use of insulin or diabetes medicines, diet, and exercise. Home blood sugar testing will help you determine whether your blood sugar is within your target range. If you have had very low blood sugar, you may be tempted to let your sugar level run high so that you do not have another low blood sugar problem. But it is most important that you keep your blood sugar in your target range. You can do this by following your treatment plan and checking your blood sugar regularly.

Sometimes a pregnant woman can get diabetes during her pregnancy. This is called gestational diabetes. Blood sugar levels are checked regularly during the pregnancy to keep levels within a target range.

Children who have diabetes need their parents' help to keep their blood sugar levels in a target range and to exercise safely. Be sure that children learn the symptoms of both high and low blood sugar so they can tell others when they need help. There are many support groups and diabetes education centres to help parents and children understand about blood sugar, exercise, diet, and medicines.

Teens especially may have a hard time keeping their blood sugar levels in control because their bodies are growing and developing. Also, they want to be with their friends and eat foods that may affect their blood sugar. Having diabetes during the teenage years is not easy. But your teen is at an excellent age to understand the disease and its treatment and to take over some of the responsibilities of his or her care.

If your blood sugar level reads too high or too low but you are feeling well, you may want to recheck your sugar level or recalibrate your blood glucose meter. The problem may be with either your blood sample or the machine.

High blood sugar (hyperglycemia)

High blood sugar occurs when the sugar (glucose) level in your blood rises above your target range. Eating too many calories, missing medicines (insulin or pills), or having an infection or illness, injury, surgery, or emotional stress can cause your blood sugar to rise.

High blood sugar usually develops slowly over a period of hours to days. But missing a dose of insulin can cause a rapid rise in blood sugar levels. Blood sugar levels just above your target range may make you feel tired and thirsty. If your blood sugar level stays higher than your target range for weeks, your body will adjust to that level, and you may not have as many symptoms of high blood sugar.

Unless you don't monitor your blood sugar regularly or you don't notice the symptoms of high blood sugar, you usually will have time to treat high blood sugar so that you can prevent high blood sugar emergencies. Three things can help you prevent high blood sugar problems:

  • Test your blood sugar often, especially if you are sick or are not following your normal routine. You can see when your blood sugar is above your target range, even if you don't have symptoms of high blood sugar such as increased thirst, increased urination, and fatigue. Then you can treat it early, preventing an emergency.
  • Call your doctor if you have frequent high blood sugar levels or if your blood sugar level is consistently staying above your target range. Your medicine may need to be adjusted or changed.
  • Drink extra water or non-caffeinated, non-sugared drinks so you will not be dehydrated. If your blood sugar continues to rise, your kidneys will increase the amount of urine produced, and you can become dehydrated.

Complications of high blood sugar can cause serious problems, including coma and death. Over time, high blood sugar can damage your eyes, heart, kidneys, blood vessels, and nerves.

Low blood sugar (hypoglycemia)

Low blood sugar occurs when the sugar (glucose) level in your blood drops below what your body needs. Not eating enough food or skipping meals, taking too much medicine (insulin or pills), exercising more than usual, or taking certain medicines that lower blood sugar can cause your blood sugar to drop rapidly. Do not drink alcohol if you have problems recognizing the early signs of low blood sugar.

People who lose weight or develop kidney problems may not need as much insulin or other medicines as they did before they lost the weight or developed kidney problems. Their blood sugar may drop too low. Be sure to check your blood sugar often when your body goes through changes.

When your blood sugar level drops below 4.0 millimoles per litre (mmol/L), you will usually have symptoms of low blood sugar. This can develop quickly, in 10 to 15 minutes.

    • If your blood sugar level drops just slightly below your target range (mild low blood sugar), you may feel tired, anxious, weak, shaky, or sweaty, and you may have a rapid heart rate. If you eat something that contains sugar, these symptoms may last only a short time. If you have diabetes, you may not always notice symptoms of mild low blood sugar. This is called hypoglycemia unawareness. If your blood sugar is well controlled and does not change much during the day, you may have an increased risk for hypoglycemic unawareness.
    • If your blood sugar level continues to drop, your behaviour may change. Symptoms of moderate low blood sugar may start. You may become too weak or confused to eat something to raise your blood sugar level.
    • If your blood sugar level drops very low, you may lose consciousness or have a seizure. If you have symptoms of severe low blood sugar, you need medical care immediately.

You may have symptoms of low blood sugar if your blood sugar drops from a high level to a lower level. For example, if your blood sugar level has been higher than 17.0 mmol/L for a week or so and the level drops suddenly to 5.0 mmol/L, you may have symptoms of low blood sugar even though your blood sugar is in the target range. But if you have had diabetes for many years, you may not have symptoms of low blood sugar until your blood sugar level is very low.

If your doctor thinks you have low blood sugar levels but you are not having symptoms, he or she may ask you to check your blood sugar more often. Your doctor may ask you to check your blood sugar in the middle of the night or to do a 3-day test using a continuous glucose monitor.

Check your symptoms to decide if and when you should see a doctor.

Check Your Symptoms

Do you have diabetes?
Yes
Diabetes
No
Diabetes
How old are you?
Less than 3 years
Less than 3 years
3 years or older
3 years or older
Are you male or female?
Male
Male
Female
Female

The medical assessment of symptoms is based on the body parts you have.

  • If you are transgender or non-binary, choose the sex that matches the body parts (such as ovaries, testes, prostate, breasts, penis, or vagina) you now have in the area where you are having symptoms.
  • If your symptoms aren’t related to those organs, you can choose the gender you identify with.
  • If you have some organs of both sexes, you may need to go through this triage tool twice (once as "male" and once as "female"). This will make sure that the tool asks the right questions for you.
Did you pass out completely (lose consciousness)?
Yes
Lost consciousness
No
Lost consciousness
If you are answering for someone else: Is the person unconscious now?
(If you are answering this question for yourself, say no.)
Yes
Unconscious now
No
Unconscious now
Are you back to your normal level of alertness?
After passing out, it's normal to feel a little confused, weak, or light-headed when you first wake up or come to. But unless something else is wrong, these symptoms should pass pretty quickly and you should soon feel about as awake and alert as you normally do.
Yes
Has returned to normal after loss of consciousness
No
Has returned to normal after loss of consciousness
Did the loss of consciousness occur during the past 24 hours?
Yes
Loss of consciousness in past 24 hours
No
Loss of consciousness in past 24 hours
Have you had a seizure?
Yes
Seizure
No
Seizure
Is your blood sugar low?
Symptoms of low blood sugar may be mild at first but can quickly get worse.
Yes
Low blood sugar
No
Low blood sugar
Do you have a plan for dealing with low blood sugar?
If you haven't used your plan or don't have one, take steps to get your blood sugar back up.
Yes
Has plan for managing low blood sugar
No
Has plan for managing low blood sugar
Are your symptoms:
It may take up to 30 minutes after you eat a quick-sugar food before you can tell how it is affecting your blood sugar.
Getting worse?
Symptoms are getting worse
Staying the same (not worse or better)?
Symptoms are the same
Getting better?
Symptoms are getting better
Are you concerned that you are having episodes of low blood sugar more often than in the past?
Yes
Increased episodes of low blood sugar
No
Increased episodes of low blood sugar
Do you think you may be dehydrated?
Yes
May be dehydrated
No
May be dehydrated
Are the symptoms severe, moderate, or mild?
The symptoms in an adult or older child are different than the symptoms in a baby or toddler.
Severe
Severe dehydration
Moderate
Moderate dehydration
Mild
Mild dehydration
Are you having trouble drinking enough to replace the fluids you've lost?
Little sips of fluid usually are not enough. You need to be able to take in and keep down plenty of fluids.
Yes
Unable to maintain fluid intake
No
Able to maintain fluid intake
Has there been a decrease in how alert or aware you are or how well you can think and respond?
Yes
Decreased level of consciousness
No
Decreased level of consciousness
Do you have symptoms of a serious illness?
The symptoms in an adult or older child are different than the symptoms in a baby or toddler.
Yes
Symptoms of serious illness
No
Symptoms of serious illness
Is your blood sugar high?
Yes
High blood sugar
No
High blood sugar
If you are an adult, is your blood sugar >34 mmol/L? If you are younger than 18, is your blood sugar >14 mmol/L?
Be sure to double-check a high blood sugar. If it's not higher than the number given for your age group but you're worried about it anyway, answer yes.
Yes
Blood sugar over 34 mmol/L
No
Blood sugar over 34 mmol/L
Do you have symptoms of diabetic ketoacidosis?
Yes
Symptoms of diabetic ketoacidosis
No
Symptoms of diabetic ketoacidosis
Does your urine contain a moderate to large amount of ketones?
Ketones are a sign that your blood sugar is getting out of control. There is a urine test for ketones that you can do at home.
Yes
Moderate to large amount of ketones in urine
No, or you haven't tested your urine
Less than moderate amount of ketones in urine (or has not tested urine)
Are there any symptoms of infection?
Yes
Symptoms of infection
No
Symptoms of infection
Do you have a plan for dealing with high blood sugar?
Yes
Has plan for managing blood sugar
No
Has plan for managing blood sugar
Is the plan helping get your blood sugar under control?
Yes
Plan is helping get blood sugar under control
No
Plan is helping get blood sugar under control
Are you concerned that you are having episodes of high blood sugar more often than in the past?
Yes
Increased episodes of high blood sugar
No
Increased episodes of high blood sugar
Have you been sick with anything worse than a cold for more than 2 days?
Yes
Sick for more than 2 days
No
Sick for more than 2 days
Are you concerned about how to keep your blood sugar in the target range?
Yes
Concerns about managing blood sugar
No
Concerns about managing blood sugar

Many things can affect how your body responds to a symptom and what kind of care you may need. These include:

  • Your age. Babies and older adults tend to get sicker quicker.
  • Your overall health. If you have a condition such as diabetes, HIV, cancer, or heart disease, you may need to pay closer attention to certain symptoms and seek care sooner.
  • Medicines you take. Certain medicines, such as blood thinners (anticoagulants), medicines that suppress the immune system like steroids or chemotherapy, or natural health products can cause symptoms or make them worse.
  • Recent health events, such as surgery or injury. These kinds of events can cause symptoms afterwards or make them more serious.
  • Your health habits and lifestyle, such as eating and exercise habits, smoking, alcohol or drug use, sexual history, and travel.

Try Home Treatment

You have answered all the questions. Based on your answers, you may be able to take care of this problem at home.

  • Try home treatment to relieve the symptoms.
  • Call your doctor if symptoms get worse or you have any concerns (for example, if symptoms are not getting better as you would expect). You may need care sooner.
HomeTreatment
RelatedInformation

Symptoms of serious illness may include:

  • A severe headache.
  • A stiff neck.
  • Mental changes, such as feeling confused or much less alert.
  • Extreme fatigue (to the point where it's hard for you to function).
  • Shaking chills.

Symptoms of serious illness in a baby may include the following:

  • The baby is limp and floppy like a rag doll.
  • The baby doesn't respond at all to being held, touched, or talked to.
  • The baby is hard to wake up.

You can get dehydrated when you lose a lot of fluids because of problems like vomiting or fever.

Symptoms of dehydration can range from mild to severe. For example:

  • You may feel tired and edgy (mild dehydration), or you may feel weak, not alert, and not able to think clearly (severe dehydration).
  • You may pass less urine than usual (mild dehydration), or you may not be passing urine at all (severe dehydration).

Severe dehydration means:

  • Your mouth and eyes may be extremely dry.
  • You may pass little or no urine for 12 or more hours.
  • You may not feel alert or be able to think clearly.
  • You may be too weak or dizzy to stand.
  • You may pass out.

Moderate dehydration means:

  • You may be a lot more thirsty than usual.
  • Your mouth and eyes may be drier than usual.
  • You may pass little or no urine for 8 or more hours.
  • You may feel dizzy when you stand or sit up.

Mild dehydration means:

  • You may be more thirsty than usual.
  • You may pass less urine than usual.

Severe dehydration means:

  • The baby may be very sleepy and hard to wake up.
  • The baby may have a very dry mouth and very dry eyes (no tears).
  • The baby may have no wet diapers in 12 or more hours.

Moderate dehydration means:

  • The baby may have no wet diapers in 6 hours.
  • The baby may have a dry mouth and dry eyes (fewer tears than usual).

Mild dehydration means:

  • The baby may pass a little less urine than usual.

Early symptoms of low blood sugar may include:

  • Sweating.
  • Feeling nervous, shaky, and weak.
  • Extreme hunger and slight nausea.
  • Dizziness and headache.
  • Blurred vision.
  • Confusion.

If blood sugar continues to drop, you may start to have more severe symptoms.

You can test for ketones at home using special tablets or test strips. Ketones are substances made by the body when it burns fat instead of sugar. They are a sign that your blood sugar is out of control.

To do the urine test:

  • Collect a urine sample in a clean container.
  • Follow the directions on the test.
  • If either the test strip or the urine changes colour when the tablet is dropped into the sample, the urine sample contains ketones.
  • Test results may range from negative to 4+, from small to large, or from low to high. (For tests that read from negative to 4+, more than 1+ means that you have a moderate to large amount of ketones in your urine.)

Some home blood sugar meters can also measure blood ketones. You use the same finger-prick method that you use to measure blood sugar.

Symptoms of infection may include:

  • Increased pain, swelling, warmth, or redness in or around the area.
  • Red streaks leading from the area.
  • Pus draining from the area.
  • A fever.

Symptoms of diabetic ketoacidosis may include:

  • Flushed, hot, dry skin.
  • Blurred vision.
  • Drowsiness or difficulty waking up.
  • Fast, deep breathing.
  • Fruity breath odour.
  • Belly pain, loss of appetite, and vomiting.
  • Confusion.

Here is what you can do to treat low blood sugar. If at any point during these steps you think you are getting worse, seek care immediately.

  • Eat some quick-sugar food, such as 3 to 4 glucose tablets, 1 tablespoon (15 mL) of sugar, 1 tablespoon (15 mL) of honey, 2/3 cup (150 mL) of fruit juice or regular (not diet) soda pop, or hard candy (such as 6 Life Savers).
  • Wait about 15 minutes. Then check your blood sugar.
    • If your blood sugar is above 4.0 millimoles per litre (mmol/L) and your symptoms have improved, you can go back to your regular schedule of meals and snacks.
    • If your blood sugar is still low, eat another quick-sugar food, wait 15 minutes, and check your blood sugar again. If your blood sugar is still below 4.0 millimoles per litre (mmol/L), you may need medical care soon.

Seek Care Today

Based on your answers, you may need care soon. The problem probably will not get better without medical care.

  • Call your doctor today to discuss the symptoms and arrange for care.
  • If you cannot reach your doctor or you don't have one, seek care today.
  • If it is evening, watch the symptoms and seek care in the morning.
  • If the symptoms get worse, seek care sooner.
HomeTreatment
RelatedInformation

Call 9-1-1 Now

Based on your answers, you need emergency care.

Call 9-1-1 or other emergency services now.

Sometimes people don't want to call 9-1-1. They may think that their symptoms aren't serious or that they can just get someone else to drive them. But based on your answers, the safest and quickest way for you to get the care you need is to call 9-1-1 for medical transport to the hospital.

Seek Care Now

Based on your answers, you may need care right away. The problem is likely to get worse without medical care.

  • Call your doctor now to discuss the symptoms and arrange for care.
  • If you cannot reach your doctor or you don't have one, seek care in the next hour.
  • You do not need to call an ambulance unless:
    • You cannot travel safely either by driving yourself or by having someone else drive you.
    • You are in an area where heavy traffic or other problems may slow you down.

Make an Appointment

Based on your answers, the problem may not improve without medical care.

  • Make an appointment to see your doctor in the next 1 to 2 weeks.
  • If appropriate, try home treatment while you are waiting for the appointment.
  • If symptoms get worse or you have any concerns, call your doctor. You may need care sooner.
HomeTreatment
RelatedInformation

Home Treatment

Manage your blood sugar level

When you have diabetes, whether it is type 1 diabetes, type 2 diabetes, or gestational diabetes, one of the most important skills you will learn is how to manage your blood sugar level.

Following your doctor's instructions on the use of insulin or diabetes medicines, diet, and exercise will help you avoid blood sugar problems. You will learn to recognize the symptoms and distinguish between high and low blood sugar levels. It may be hard for a parent of a young child to distinguish the difference between high and low blood sugar symptoms in a child.

When you have learned to recognize high or low blood sugar levels, you can take the appropriate steps to bring your blood sugar level back to your target blood sugar levels.

People who keep their blood sugar levels under control with diet, exercise, or oral diabetes medicines are less likely to have problems with high or low blood sugar levels. Do not drink alcohol if you have problems recognizing the early signs of low blood sugar.

Learn how to deal with high blood sugar levels

Be sure to know the steps for dealing with high blood sugar and how fast your insulin medicine will work to bring your blood sugar down. Some insulins work very fast while regular insulin takes a little longer to bring the sugar level down. Knowing how fast your insulin works will keep you from using too much too quickly.

Learn how to deal with low blood sugar levels

Because you have diabetes and can have low blood sugar levels, you need to keep some glucose or sucrose tablets or solution or quick-sugar food with you at all times. These can quickly raise your blood sugar level. Be sure to check your blood sugar level 15 minutes after eating a quick-sugar (carbohydrate) food to make sure your level is getting back to your target range. If you continue to have low blood sugar, take another 15 grams of carbohydrate. When your blood sugar gets to 4.0 mmol/L or higher, you can eat your normal meals and snacks. Eat a small snack if your next meal or snack is more than one hour away.

Quick sugar foods to help raise blood sugar footnote 1

Food

Amount (15 g of carbohydrate)

Glucose tablets (preferred choice)

3 tablets

Table sugar

1 tablespoon (15 mL) dissolved in water

Fruit juice or regular soda pop

2/3 cup (150 mL)

Honey (do not give to children younger than 1 year old)

1 tablespoon (15 mL)

Candy like Life Savers

6 pieces

It is important to know that sugar foods like a candy bar or ice cream do not help raise low blood sugar levels quickly, because these foods also have fat and protein. So the body can't use the sugar (carbohydrate) in these foods quickly to raise the blood sugar level.

You can get low blood sugar from using too much insulin or from other medicines you take.

Parents need to help their child learn to treat a low blood sugar level.

Pregnant women who have gestational diabetes also need to know how to deal with a low blood sugar level.

Since low blood sugar levels can quickly become a medical emergency, be sure to wear medical identification, such as a medical alert bracelet, to let people know you have diabetes so they can get help for you.

If you have severe symptoms of low blood sugar, someone else may need to give you a shot of glucagon. If this occurs, be sure to call your doctor immediately to let him or her know this has happened.

Symptoms to watch for during home treatment

Call your doctor if any of the following occur during home treatment:

Prevention

Take steps to control your blood sugar level

Although high blood sugar (hyperglycemia) and low blood sugar (hypoglycemia) have very different symptoms and treatments, they are both caused by blood sugar and insulin imbalances. The steps you take to control your blood sugar level will help prevent both high and low blood sugar levels.

Be sure to have identification that says you have diabetes, such as a medical alert bracelet, with you at all times. This will help other people take steps to care for you if you are not able tell them about your medical condition.

You can take steps to prevent high and low blood sugar emergencies.

  • Follow your treatment plan.
  • Monitor your blood sugar levels regularly to detect early changes before an emergency develops. Treat your symptoms of high or low blood sugar quickly to prevent more problems.
  • Control your stress to prevent your blood sugar level from increasing slowly over several days.
  • Limit how much alcohol you drink. Do not drink alcohol if you have problems recognizing the early signs of low blood sugar.
  • Take precautions when you are driving and do not drive if your blood sugar is low.

Monitoring and controlling blood sugar levels

Use home blood sugar tests to determine whether your blood sugar is in your target range. Work with your doctor to set your individual treatment goals. If you can consistently maintain this level of control, you will have very few blood sugar level emergencies.

Parents can help their child learn how to prevent low blood sugar levels and high blood sugar levels.

Control stress

No matter how skilled you are at monitoring and controlling your blood sugar levels, you are still at risk for high or low blood sugar levels that are brought on by stressful situations. Stress can affect your body's blood sugar levels in two ways:

  • It can increase hormones that give you energy. This may cause your blood sugar to go up.
  • It can cause you to change the way you take care of yourself, a problem for all people with diabetes.

Stress can be both mental and physical. Some examples of stress include an illness, a bad day at work, and a tough problem at home. When you are under stress, your blood sugar levels change. For more information, see the topic Stress Management.

Blood sugar levels and exercise

You can keep your blood sugar levels under control when you exercise, so that you do not become too hungry or make your blood sugar level drop. There are two ways to keep your blood sugar levels under control:

  1. At the meal before your planned exercise, you can take less insulin, OR
  2. Before you exercise, eat some carbohydrate.

Keep a quick-sugar food with you during exercise in case your blood sugar level drops low.

Vaccinations

Your doctor may recommend that you get vaccinations, such as a flu vaccine or pneumococcal vaccine, to prevent you from those illnesses.

Other places to get help

Diabetes Canada has a lot of information on diabetes and can link you to support groups. For more information, call 1-800-BANTING (1-800-226-8464) or see the organization's website: www.diabetes.ca.

Preparing For Your Appointment

Questions to prepare for doctor appointment

You can help your doctor treat your condition by being prepared to answer the following questions:

  • What steps did you take to correct your high or low blood sugar level? Did they help?
  • Have you had signs of another illness?
  • Have you made any recent changes in your diet, exercise, or medicines?
  • What other prescription and non-prescription medicines do you take?
  • Have you recently had increased emotional or physical stress?
  • Have you noticed situations that trigger or may cause your high or low blood sugar problem?
  • Have you noticed any patterns, such as time of day, when your high or low blood sugar problem occurs?
  • Have you used a high blood sugar card ? If so, be sure to bring it when you see your doctor.
  • Do you have other health risks?

Be sure to take your daily blood sugar (glucose) monitoring logbook to your appointment. If you have specific records of your high and low blood sugar problems, be sure to take those records.

Parents will also need to keep records of their child's high or low blood sugar problems to share with their child's doctor.

References

Citations

  1. Diabetes Canada Clinical Practice Guidelines Expert Committee, et al. (2018). Targets for glycemic control. Canadian Journal of Diabetes, 42(Suppl 1): S42–S46. DOI: 10.1016/j.jcjd.2017.10.030. Accessed October 15, 2018.

Credits

Adaptation Date: 1/19/2023

Adapted By: HealthLink BC

Adaptation Reviewed By: HealthLink BC