Hypoglycemia (Low Blood Sugar)

A blood sugar level lower than about 3.3 mmol/L (60 mg/dL) is called hypoglycemia. The feelings associated with hypoglycemia are called an “insulin reaction.”

The earliest symptoms of low blood sugar can be like the feelings many people experience when they’ve gone without food for a long time: they may feel hungry, tired and irritable, and may even have a headache. These early warning signs tell us that the body needs sugar quickly. As the blood sugar continues to drop, other signs and symptoms may develop—shakiness, pale skin, cold sweat, dilated pupils, and pounding heart. These happen because the body is trying to boost the blood sugar from within. Certain hormones, including glucagons, adrenaline, cortisol, and growth hormone, stimulate our liver and muscles to convert stored sugar into glucose, which enters the bloodstream.

In someone without diabetes​, the body turns off the insulin supply whenever blood sugar is at a normal level. But in people with diabetes, the injected insulin continues to work. As fast as the glucose enters the bloodstream, the insulin pushes it into the cells, so the level of sugar in the blood remains low until the person takes extra sugar by mouth.

Most people with type 1 diabetes have low blood sugar reactions from time to time – an average of about two mild ones per week. Indeed, mild reactions that are easily recognized and treated, without too much interruption in activities, should be expected. They can be seen as the price paid for good glucose control. Note that some people have symptoms of hypoglycemia even when their blood sugar level is higher than 3.3 mmol/L (60 mg/dL).

Common signs and symptoms of a mild insulin reaction

  • shakiness: “butterflies,” feeling nervous for no reason
  • cold, clammy sweatiness, unlike sweat from playing hard
  • dilated pupils, “funny-looking” eyes
  • mood change: irritable, grouchy, impatient; temper tantrums in younger children
  • hunger, and sometimes nausea due to the hunger
  • lack of energy: tired, weak, floppy
  • lack of concentration
  • blurred vision
  • pounding heart
  • change in skin colour: pale, most noticeable in the face and around the mouth
  • disturbed sleep: restlessness, crying out, sleepwalking, or nightmares

Usually insulin reactions happen suddenly, over a period of minutes rather than hours. While they may occur at any time of the day or night, they happen most often when insulin is working at its peak.

Low blood sugar symptoms vary from child to child. Each child tends to develop his own set of symptoms. After 1 or 2 episodes, you and your child will learn to recognize an insulin reaction quickly.  It is helpful if you explain your child’s specific symptoms to teachers, coaches, school bus drivers, and other caregivers. Even young children can be taught to tell an adult about these symptoms. They could use a specific phrase such as “I feel funny” or “I need sugar.”

Hypoglycemia may be most difficult to detect in infants or toddlers, who can’t describe their feelings. A sudden change in behaviour, with irritability, crying, pale face and “floppiness” may be the tip-off that blood sugar is too low.

How to treat a mild insulin reaction

All insulin reactions must be treated right away. Always have a source of fast-acting sugar available, such as juice, dextrose tablets, or even table sugar.

If possible, check the blood sugar level to confirm hypoglycemia. A blood glucose level lower than 4 mmol/l (about 72 mg/dl) in older children and teens or below 6 mmol/L (110 mg/dL) in toddlers or preschoolers, along with symptoms of low blood sugar should be treated. (If you are unable to check the blood sugar before treating the reaction, check it as soon as possible afterward. Note the response to treatment.)

Give a source of quick-acting sugar. About 10 to 15 grams of carbohydrates is all it takes to treat an insulin reaction. Examples include:

  • four ounces (125 mL) of unsweetened juice or regular soft drink
  • two to three dextrose tablets – these are not appropriate for infants or toddlers
  • eight ounces (250 mL) of milk
  • two teaspoons (10 mL) of sugar
  • prepackaged glucose gels may also be available from your pharmacy or diabetes supply shop. Read the label ahead of time to determine the amount you should give to treat a low blood sugar reaction. An amount that will supply 10 to 15 grams of carbohydrate is generally recommended.

For infants or toddlers, some parents keep a tube of cake frosting handy for treating mild hypoglycemia.

If a mild reaction occurs just before a meal or snack, start the meal or snack immediately, beginning with some simple carbohydrates.

  • Wait for the sugar to take effect. This is the hardest part. People who experience hypoglycemia feel extremely hungry and scared. They are often tempted to continue to eat and drink until the symptoms go away. This may result in a high blood sugar level later in the day. If symptoms last, recheck the blood sugar in 10 to 15 minutes. If it is still low, the child should have an extra 10 to 15 grams of carbohydrate. If vigorous exercise is anticipated prior to the next meal or snack, or if the reaction occurs during the night, the simple carbohydrate should be followed with a complex carbohydrate (one from the starch category).
  • Try to figure out the cause of the insulin reaction. If there is no apparent reason, consider reducing the appropriate insulin by 10% to 20% the next day.
  • Note the blood sugar levels, time, response, and possible cause of the reaction in your record book.

Note: If in doubt, treat. When you can’t check the blood sugar level to confirm an insulin reaction, give sugar to be safe.

False low blood sugar reactions

Sometimes children feel anxious, nervous or tired and think it’s due to low blood sugar when it isn’t. There are many reasons for this. A quick blood sugar check is the best way to find out whether or not the blood sugar is low. Sometimes low blood sugar symptoms occur when the blood sugar drops quickly from a high to a normal level. Feeling nervous or upset for other reasons, such as exams, can also be confused with hypoglycemia. And occasionally the symptoms of high blood sugar are mistaken for a low sugar reaction. Once the blood glucose has been checked and it is clear that the result is over 6 mmol/L, reassure the child and encourage her to resume activity. However, if in doubt, treat the symptoms.

Why do insulin reactions occur?

Understanding the reasons for hypoglycemia is key to preventing it. The causes are usually related to the three major factors affecting blood sugar balance: insulin, food and activity.

Too much insulin

Children can get too much insulin if:

  • the wrong amount is given
  • the dose is mistakenly given at the wrong time, such as giving the pre-breakfast dose at suppertime
  • the dose isn’t reduced when blood sugar readings are consistently less than the target level.

Not enough food

This can happen easily enough—for example, when children get caught up in their activities and forget to eat, when toddlers sleep through snack time, or when teens sleep through breakfast or skip a meal.

Too much unplanned activity

This is the most frequent cause of hypoglycemia, because children aren’t used to planning ahead before they jump into an active game like tag or football. That’s why the blood glucose target range is wider in younger children than in adults; it allows for such spontaneity. Children should be able to enjoy any sport or activity with planning.

How many insulin reactions are too many?

It is not unusual to have one or two mild reactions per week that can be easily treated with juice. However, these mild reactions can interrupt the school day or other activities, and make it difficult for your child to focus for the following half hour or so. Prevent them as best you can, and respond to them quickly. If your child often has lows, this needs to be addressed with a change to the regimen. For example, if the teacher notices that your child is cranky every day at 11:30 a.m. and low blood sugar is confirmed, it’s time to re-examine the meal plan or insulin dose and make a change.

What are the long-term effects of a severe low?

The greatest long-term effect is the fear that the child will have another severe insulin reaction. This is a very real fear for many parents, siblings, and children with diabetes. It can make people reluctant to keep trying to maintain good blood sugar control. This psychological setback is the only real long-term impact, because the body works very hard to protect the brain during events like this. Mildly delayed intellectual development has been noted in some babies who had repeated episodes of severe hypoglycemia in the first three to five years of life.

Reducing the risk of hypoglycemia

Low blood sugar reactions are not always preventable, but there are things you can do to keep them to a minimum.

  • Eat meals and snacks on time. A delay of half an hour or more can result in hypoglycemia. This is most important for youngsters on Humulin N or Novolin NPH.
  • Make sure that the proper insulin dose is prepared and given. Children require close supervision with this task.
  • Plan for extra activity with extra food or an insulin reduction. Set up a good communication system with teachers, coaches, and other leaders so you’ll know when extra activity is planned.
  • Set up realistic blood sugar targets with your health care team. For example, it may be inappropriate and even dangerous to aim for “normal” blood sugar levels in very young children.
  • Remember to lower the insulin dose if the sugar level is lower than the target at the same time of day 2 days in a row, or 3 times in a week.
  • Always have some form of quick-acting sugar close by—and make sure everyone knows where it is.
  • Always have a glucagon kit at home. Review its use regularly. Take it with you on vacation. Replace it when it reaches its expiry date, and practice preparing it before you throw it out.
  • Encourage your child to wear medical-alert identification, and to carry a wallet card if older.

Marcia Frank, RN, MHSc, CDE

Denis Daneman, MB, BCh, FRCPC