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Topic 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, 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.

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 normal. 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 normal 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 70 milligrams per deciliter (mg/dL), 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 (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 normal 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.