Blood Glucose Levels

When blood glucose levels are too high over long periods, damage to the heart, blood vessels, eyes, and kidneys can result. Damage to the heart and blood vessels can lead to heart attack and stroke.

Skipping meals, eating too much or too little, exercising too much or too little, illness, and emotional stress can cause blood sugar levels to become too high or too low. It is important to learn how to detect the signs of low blood glucose and high blood glucose and know what to do in each case. Talk with a qualified health care provider, dietician, or nurse educator about how to handle each of these situations.

Signs of low blood glucose levels (also called low blood sugar or hypoglycemia) include confusion, irritability, and tiredness. If the blood glucose level is below 70 mg/dL, try one of the following suggestions:

  • Drink one cup of milk.
  • Drink ½ cup of fruit juice or soft drink (not diet).
  • Take 2-3 glucose tablets.
  • Eat 1 or 2 tablespoons of sugar or honey.

Check glucose levels again after about 15 minutes. If levels are still below 70 mg/dL, repeat one of the suggestions above.

Signs of high blood glucose levels (also called high blood sugar or hyperglycemia) include the following:

  • Blurred vision
  • Excessive thirst
  • Fatigue
  • Frequent urination

If the blood glucose level is less than 240 mg/dL, exercise may help bring it down. If the blood glucose is over 240 mg/dL, check the urine for ketones. If the urine has ketones, do not exercise. Be sure to talk to a health care provider in advance about how to handle this situation.

A good way to prevent blood glucose levels from going out of balance is to follow a diabetes care plan as closely as possible. Talk with a health care provider about preparing for special situations such as holiday parties, vacation travel, or illnesses.

With the approval of a qualified health care provider, people with diabetes may be able to drink alcohol in moderation. Moderation is defined as one drink per day for women and two drinks per day for men. One drink is equivalent to 5-ounces of wine, 12-ounces of beer, or 1½-ounces of 80 proof spirits. Changes in medication require checking for warnings against drinking alcohol.

In patients who have diabetes, maintaining a healthy weight through a good diet and regular exercise can help prevent or stop the advancement of other diseases. Talk to a qualified health care provider about how often to have blood pressure and cholesterol tested.

Publication Review By: the Editorial Staff at

Published: 01 Mar 2007

Last Modified: 23 Jul 2013