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Low Blood Sugar (Hypoglycemia) in Diabetes

What is hypoglycemia?

Hypoglycemia means low blood sugar. A blood sugar lower than 70 milligrams per deciliter (mg/dL), or 3.9 millimoles per liter (mmol/L), that is not treated can be very dangerous. Sometimes hypoglycemia is called an insulin reaction or insulin shock.

How does it occur?

Hypoglycemia is usually a side effect of diabetes treatment. It can also result from other conditions, diseases, medicines, hormone or enzyme deficiencies, or tumors.

If you have diabetes and you have too much insulin or other diabetes medicine in your blood, your blood sugar level will become too low. Some other things that can cause an abnormally low blood sugar levels when you have diabetes are:

  • exercising more than usual
  • skipping or delaying meals or snacks
  • having a meal or snack that is too small
  • not taking medicines at the right time
  • drinking too much alcohol
  • diarrhea or vomiting


If you are using insulin, you may have low blood sugar because:

  • You have accidentally used the wrong type of insulin.
  • Your insulin is no longer good because it has expired or was not stored properly.
  • You have an insulin pump that is not working properly.

What are the symptoms?

Low blood sugar can make you feel:

  • hungry
  • nervous
  • sweaty
  • shaky
  • lightheaded
  • dizzy
  • confused

For some people, a blood sugar below 90 mg/dL (5 mmol/L) can make them feel like this. For others, it takes a lower blood sugar (70 mg/dL or below) to cause these symptoms.



You should know the difference between the symptoms of low blood sugar (hypoglycemia) and high blood sugar (hyperglycemia). High blood sugar doesn't always cause symptoms, but when it does the symptoms may include blurry vision, extreme thirst, and a lot of urination.

How is it treated?

If you often have symptoms of hypoglycemia, you should see your healthcare provider. Your provider can help you determine the cause. Your provider will also give you guidelines for treating low blood sugar when you are having symptoms.

When you see your provider, be sure to take your notebook or glucose meter with all of the results of your recent blood sugar checks. This helps your provider know whether you are on the right medicines and are taking the right dose at the right time of day. Without this record, it is harder for your provider to help you figure out the cause of your symptoms.

Here are some examples of guidelines your provider may give you:

  • If you have diabetes and you think your blood sugar may be too low, check it with your home meter before treatment, if possible.
  • Always carry some form of sugar you can eat as soon as you have any symptoms of hypoglycemia. The following amounts and types of foods will bring your blood sugar level up:
    • 2 to 5 glucose tablets
    • 1/2 cup (4 oz) fruit juice
    • 1/2 cup (4 oz) regular (not diet) soda (about half a can)
    • 6 to 8 ounces of skim milk
    • 1/4 to 1/3 cup of raisins
    • 5 to 7 pieces of hard candy like Lifesavers
    • a tube of glucose in gel form (such as InstaGel or MonGel)
    • 1 tablespoon of molasses, corn syrup, or honey
  • If you still have symptoms 10 to 15 minutes after eating or drinking one of the foods listed above, you may need to eat or drink another portion.
  • If you are about to eat a meal, eat the fruit or drink the juice first and then eat the rest of your meal.
  • After 15 minutes, check your blood sugar again. If it is still lower than 70 milligrams per deciliter (mg/dL), take another serving of one of the foods on the list. Repeat these steps until your sugar is above 70 or until you feel better. You may need to eat a snack or meal soon after you feel better to keep your blood sugar from getting too low again.

The diabetes medicines Precose (acarbose) and Glyset (miglitol) keep your body from absorbing some types of sugar. If you have low blood sugar and you are taking these medicines, you must use glucose tablets or gel, or honey or fruit, to raise your blood sugar.

If you have diabetes, you need to know how to recognize and treat low blood sugar right away to bring it back up to a healthy range. Low blood sugar is a very serious condition and if you don't take action right away you could pass out, have a seizure, or even die. You should not go to bed until you have raised your sugar back into your normal range.

If your symptoms get worse despite treatment, call your healthcare provider or have a family member or friend call 911. Emergency treatment may include a shot of glucose or a medicine called glucagon to raise your blood sugar. You may need to go to the hospital to be treated with intravenous (IV) glucose. Being at the hospital will also allow your healthcare provider to watch your reaction to treatment, determine why you had severe hypoglycemia, and, if necessary, change your medicine dosages.

If you tend to have episodes of low blood sugar, talk with your healthcare provider about whether you should have a medicine called glucagon on hand. It can be given as a shot by a family member when you are having low blood sugar but are not alert enough to safely take some food or give yourself the shot. It makes your blood sugar rise quickly. Your family members should also know how to use your glucose meter to check your blood sugar when you are not able to. However, if you are unconscious, they should call 911 to get help on the way before trying to check your sugar and treat your low blood sugar.

How long will the effects last?

The effects of low blood sugar will continue and may even get worse until treatment brings your blood sugar level back to normal. It may take several minutes for the symptoms to go away after you start treatment. This may be a temporary problem while you and your healthcare provider are adjusting your medicine. If you are always prone to having low blood sugar, you may need to take special care for the rest of your life to keep your blood sugar at the proper level.

How can I take care of myself?

  • Keep your blood sugar in the normal range. Check your blood sugar level regularly according to your healthcare provider's recommendation and whenever you have any of the symptoms of hypoglycemia. Know when to check your blood sugar and when to call for help. Ask your healthcare provider for guidelines to help you know when to call for help.
  • Carry sugar or hard candy to eat so if your blood sugar gets too low you can treat it right away.
  • Be careful not to drive when your blood sugar is low. Driving with a low blood sugar is very dangerous, both for you and for others. The effect of a low blood sugar on your judgment, reflexes, and ability to react are similar to those of a person driving under the influence of alcohol. It's a good idea to check your sugar before you get in the driver's seat, especially on long trips. Always keep a quick source of sugar with you. Pull over to the side of the road right away if you begin to feel symptoms of low blood sugar and take your emergency sugar. Do not try to treat low blood sugar while you are driving.
  • If you are taking insulin, discuss with your healthcare provider whether you should carry the medicine glucagon with you at all times. A family member or friend can be taught how to give you a shot of glucagon if you become unconscious or unable to swallow liquids or food safely. After they give you the shot, they should call 911. The glucagon should raise your blood sugar enough for you to become conscious in a few minutes. Then, when you are awake enough, you can eat or drink something sweet, such as orange juice. If you have an episode of unconsciousness from hypoglycemia, you need to see your provider to determine why you developed hypoglycemia.
  • Call your healthcare provider if:
    • You are less than 65 years old and you notice that your blood sugar has been below 50 two or more times in 1 week.
    • You are 65 years old or older and you notice that your blood sugar has been below 70 two or more times in 1 week.
    This could be a sign that you and your provider need to change your diabetes treatment plan.

How can I prevent insulin-reaction hypoglycemia?

  • Check your blood sugar regularly.
  • Know what causes low blood sugar.
  • Eat at regular mealtimes. Do not delay or skip meals and do not eat partial meals.
  • Take all medicines exactly as prescribed.
  • Check your blood sugar more often when you are exercising more or eating less, or when you are sick, according to your healthcare provider's recommendations.
  • Keep your follow-up appointments with your provider.

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