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Diabetes-Related High and Low Blood Sugar Levels

British Columbia Specific Information

If you have diabetes and you are sick, your risk of having unpredictable blood glucose levels goes up. During these times, it is a good idea to

  • Check your blood glucose levels more often than usual (for example, every 2 to 4 hours).
  • Drink plenty of sugar-free fluids or water.
  • Check for ketones by performing a urine ketone test or blood ketone test.
  • Develop a sick-day plan with your diabetes health-care team. This should include information on:
    • Which diabetes medications you should continue and which ones you should temporarily stop
    • Guidelines for insulin adjustment if you are on insulin
    • Advice on when to contact your health-care provider or go to the emergency room.

For more information see, Diabetes Canada: Stay Safe When You Have Diabetes and Are Sick or at Risk of Dehydration

For non-emergency information or advice, call 8-1-1 to speak with a registered nurse any time of the day, every day of the year.

Overview

When you have diabetes, you may have high blood sugar levels (hyperglycemia) or low blood sugar levels (hypoglycemia) from time to time. A cold, influenza (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. Then you can help 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. You just need to follow 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 see if your blood sugar is within your target range. If you've had very low blood sugar, you may be tempted to let your sugar level run high so that you don't have another low blood sugar problem. But it's so important to keep your blood sugar in your target range. To do this, follow your treatment plan and check your blood sugar regularly.

Sometimes a woman can get diabetes during 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. Then 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. That's 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 teen years isn't easy. But it's an excellent age to understand the disease and its treatment. Your teen can take over some of the duties of their care.

If your blood sugar level reads too high or too low but you feel fine, 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. Your blood sugar can rise when you eat too many calories or miss taking your medicines (insulin or pills). It can also rise when you have an infection or illness, an injury, or surgery. Even emotional stress can cause your blood sugar to rise.

High blood sugar usually happens slowly over a period of hours to days. But missing a dose of insulin can cause a quick rise in blood sugar levels. Blood sugar levels just above your target range may make you feel tired and thirsty. If your blood sugar stays higher than your target range for weeks, your body will adjust to that level. 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 likely 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. This is even more important if you are sick or aren't following your normal routine. You can see when your blood sugar is above your target range. This is true even if you don't have symptoms such as increased thirst, increased urination, and fatigue. Then you can treat it early and prevent an emergency.
  • Call your doctor if you often have high blood sugar levels. And call if your blood sugar level consistently stays above your target range. Your medicine may need to be adjusted or changed.
  • Drink extra water or non-caffeinated, non-sugared drinks so you won't be dehydrated. If your blood sugar keeps rising, your kidneys will increase the amount of urine produced. That can make you 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. Your blood sugar can drop quickly if you don't eat enough food or you skip meals. It can also happen if you take too much medicine (insulin or pills), exercise more than usual, or take certain medicines that lower blood sugar. Do not drink alcohol if you have problems noticing 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 had 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 mmol/L, you will usually have symptoms of low blood sugar. This can happen 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 fast 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. Your risk of this is higher if your blood sugar is well controlled and doesn't change much during the day.
  • If your blood sugar level keeps dropping, your behaviour may change. You may feel more grouchy. You may become too weak or confused to eat something with sugar to raise your blood sugar level. Anytime your blood sugar drops below 4.0 mmol/L, you should act whether you have symptoms or not.
  • If your blood sugar level drops very low (usually below 2.8 mmol/L), you may lose consciousness. Or you may have a seizure. If you have symptoms of severe low blood sugar, you need medical care right away.

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. This could happen even if your blood sugar is in the target range. But if you've 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 aren't having symptoms, your doctor may ask you to check your blood sugar more often. You may need to check your blood sugar in the middle of the night. Or you may need to do a 3-day test using a continuous glucose monitor.

Health Tools

Health Tools help you make wise health decisions or take action to improve your health.

Actionsets are designed to help people take an active role in managing a health condition.

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. Or they might be concerned about the cost. 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

Self-Care

Manage blood sugar levels

One of the most important skills to learn is how to manage your blood sugar level. This is true whether you have type 1 diabetes, type 2 diabetes, or gestational diabetes.

Follow your doctor's instructions on the use of insulin or diabetes medicines, diet, and exercise. They will help you avoid blood sugar problems. You'll learn to recognize the symptoms and know if they're from high or low blood sugar levels. Then you can take the right steps to bring your blood sugar back to your target 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 noticing the early signs of low blood sugar.

Treat high blood sugar

If you have symptoms of high blood sugar, check your blood sugar. Your goal is to get your level back to your target range.

Here are ways you can treat high blood sugar.

  • If you missed a dose of your diabetes medicine, take it now. Take only the amount of medicine that you have been prescribed. Do not take more or less medicine.
  • Give yourself insulin if your doctor has prescribed it for high blood sugar.
  • Test for ketones, if your doctor told you to do so. If the results of the ketone test show a moderate to large amount of ketones, call the doctor for advice.
  • Wait 30 minutes after you take the extra insulin or the missed medicine. Check your blood sugar again.

If your symptoms or blood sugar levels are getting worse or have not improved after taking these steps, seek medical care right away.

Treat low blood sugar

You can treat low blood sugar by eating or drinking something that has 15 grams of carbohydrate. These should be quick-sugar foods. Check your blood sugar level again 15 minutes after having a quick-sugar food to make sure your level is getting back to your target range.

Children usually need less than 15 grams of carbohydrate. Check with your doctor or diabetes educator for the amount that is right for your child.

Here are examples of quick-sugar foods that have 15 grams of carbohydrate:

  • 3 to 4 glucose tablets.
  • 1 tablespoon (15 mL) of table sugar
  • 1 tablespoon (15 mL) honey
  • 2/3 cup (150 mL) of fruit juice or regular (not diet) soda.
  • Hard candy (such as 6 Life Savers)

If you have problems with severe low blood sugar, someone else may have to give you glucagon. This is a hormone that raises blood sugar levels quickly.

When to call for help during self-care

Call a doctor if any of the following occur during self-care at home:

  • Symptoms of low blood sugar, such as sweating, shakiness, extreme hunger, nausea, or dizziness.
  • Symptoms of high blood sugar, such as increased thirst, increased urination, fatigue, or light-headedness.
  • Symptoms occur more often or are more severe.

Learn more

Preparing For Your Appointment

You can help your doctor diagnose and treat your condition by being prepared for your appointment.

Credits

Current as of: March 1, 2023

Author: Healthwise Staff
Medical Review:
William H. Blahd Jr. MD, FACEP - Emergency Medicine
Kathleen Romito MD - Family Medicine
Adam Husney MD - Family Medicine