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Home > Health Library > Diabetes-Related High and Low 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 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:
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 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 70 milligrams per deciliter (mg/dL), you will usually have symptoms of low blood sugar. This can develop quickly, in 10 to 15 minutes.
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.
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Many things can affect how your body responds to a symptom and what kind of care you may need. These include:
You have answered all the questions. Based on your answers, you may be able to take care of this problem at home.
Symptoms of serious illness may include:
Symptoms of serious illness in a baby may include the following:
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:
Severe dehydration means:
Moderate dehydration means:
Mild dehydration means:
Early symptoms of low blood sugar may include:
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:
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:
Symptoms of diabetic ketoacidosis may include:
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.
Based on your answers, you may need care soon. The problem probably will not get better without medical care.
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.
Based on your answers, you may need care right away. The problem is likely to get worse without medical care.
Based on your answers, the problem may not improve without medical care.
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.
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.
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)
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.
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.
Call your doctor if any of the following occur during home treatment:
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.
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.
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:
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.
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:
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.
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.
You can help your doctor treat your condition by being prepared to answer the following questions:
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.
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: June 26, 2019
Author: Healthwise StaffMedical Review: William H. Blahd, Jr., MD, FACEP - Emergency MedicineKathleen Romito, MD - Family MedicineAdam Husney, MD - Family Medicine
Current as of: June 26, 2019
Author: Healthwise Staff
Medical Review:William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Kathleen Romito, MD - Family Medicine & Adam Husney, MD - Family Medicine
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