Our Health Library information does not replace the advice of a doctor. Please be advised that this information is made available to assist our patients to learn more about their health. Our providers may not see and/or treat all topics found herein.
Diabetes-Related High and Low Blood Sugar Levels
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 centers 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 noncaffeinated, 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.
- 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 (usually below 40 mg/dL), your behavior may change, and you may feel more irritable. You may become too weak or confused to eat something with sugar to raise your blood sugar level. Anytime your blood sugar drops below 50 mg/dL, you should act whether you have symptoms or not.
- If your blood sugar level drops very low (usually below 20 mg/dL), 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 300 mg/dL for a week or so and the level drops suddenly to 100 mg/dL, 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.
Health Tools help you make wise health decisions or take action to improve your health.
Check Your Symptoms
The medical assessment of symptoms is based on the body parts you have.
- If you are transgender or nonbinary, 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.
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, herbal remedies, or supplements 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.
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:
- Feeling nervous, shaky, and weak.
- Extreme hunger and slight nausea.
- Dizziness and headache.
- Blurred vision.
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 color 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 odor.
- Belly pain, loss of appetite, and vomiting.
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 of sugar, 1 tablespoon of honey, ½ to ¾ cup (4 to 6 ounces) 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 70 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 70, 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.
Call 911 Now
Based on your answers, you need emergency care.
Call 911 or other emergency services now.
Sometimes people don't want to call 911. 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 911 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.
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 type of food with you at all times that can quickly raise your blood sugar level. These should be quick-sugar foods (about 15 grams of carbohydrate). Be sure to check your blood sugar level again 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 70 mg/dL or higher, you can eat your normal meals and snacks. Eat a small snack if your next meal or snack is more than a few hours away.
1 tablespoon (3 teaspoons)
Fruit juice or regular soda pop
½–¾ cup (4–6 ounces)
1 cup (8 ounces)
1 tablespoon (3 teaspoons)
Candy like Life Savers
Hard candy (like Jolly Rancher)
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.
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:
- Symptoms of high blood sugar develop.
- Symptoms of low blood sugar develop.
- Symptoms become more severe or frequent.
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 below 70 milligrams per deciliter (mg/dL).
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.
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 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:
- At the meal before your planned exercise, you can take less insulin, OR
- Before you exercise, eat some carbohydrate.
Keep a quick-sugar food with you during exercise in case your blood sugar level drops low.
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
The American Diabetes Association has a lot of information on diabetes and can link you to support groups. For more information, call 1-800-DIABETES (1-800-342-2383) or see the organization's website: www.diabetes.org/home.
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 nonprescription 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?
Parents will also need to keep records of their child's high or low blood sugar problems to share with their child's doctor.
- Warshaw H, Kulkarni K (2011). The Complete Guide to Carb Counting, 3rd ed. Alexandria, VA: American Diabetes Association.
- American Diabetes Association (2013). Carbs: Fast! Diabetes Forecast. http://www.diabetesforecast.org/diabetes-101/carbs-fast.html. Accessed April 21, 2016.
- American Diabetes Association (2015). Hypoglycemia (low blood glucose). American Diabetes Association. http://www.diabetes.org/living-with-diabetes/treatment-and-care/blood-glucose-control/hypoglycemia-low-blood.html. Accessed April 21, 2016.
Current as of: February 26, 2020
Author: Healthwise Staff
William H. Blahd Jr. MD, FACEP - Emergency Medicine
Kathleen Romito MD - Family Medicine
Adam Husney MD - Family Medicine
Current as of: February 26, 2020
To learn more about Healthwise, visit Healthwise.org.
© 1995-2021 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.