Why glucose is the go-to

Jessica Oosthuizen explains why pure glucose is the preferred treatment for hypoglycaemia (low blood glucose).

“To fix a low blood glucose reading you need time, not more food.”

Hypoglycaemia remains a worry for many people living with diabetes and parents with children who have diabetes. It’s also one of the major limiting factors towards achieving good glycaemic control.

In diabetes management, when you are aiming for a blood glucose target of between 4 – 10mmol/L, it’s almost impossible to prevent hypoglycaemia all the time.

Hypoglycaemia can happen at any time of the day. Though, it may be more likely to occur before meal times, at the peak of insulin if the dose is incorrect, and during or after exercise.

Type 1 diabetes patients frequent hypoglycaemia the most. Followed by people with Type 2 diabetes managed by insulin and then people with Type 2 diabetes managed by sulfonylureas (antidiabetic drugs).

What is hypoglycaemia?

Hypoglycaemia means low blood glucose levels. It can be defined by:

  • A low blood glucose reading below 3,5 mmol/L. In children under six, this reading is below 4 mmol/L  because children may not be able to recognise symptoms or communicate with you.
  • Adrenergic and autonomic symptoms. These are symptoms caused by the body attempting to raise the blood glucose level. They include trembling, palpitations, sweating, dizziness, anxiety, hunger, nausea and tingling. These symptoms tend to start happening at a reading of between 2,8 and 4mmol/L.
  • Neuroglycopenic symptoms. These symptoms originate in the brain as a result of a deficiency of glucose in the central nervous system. These include difficulty concentrating, confusion, weakness, drowsiness, blurred vison, difficulty speaking, headache and dizziness. These symptoms are likely to occur at a reading below 2,8mmol/L.


Hypoglycaemia can be classified as mild, moderate or severe.

In mild hypoglycaemia, self-treatment is possible and blood glucose can easily be rectified to normal values.

With moderate hypoglycaemia, your body will react with warning signs, involving autonomic symptoms. You will be able to self-treat to bring blood glucose levels up.

When having a severe hypoglycaemic episode, you will require assistance from another person to give you something to eat or drink, or a glucagon injection.

In severe cases, you may lose consciousness and have seizures. Glucagon is a naturally occurring substance, produced by the pancreas, which supports the production of glucose to correct the hypoglycaemic state. This response may be slightly defective in Type 1 diabetes.

What causes hypoglycaemia?

Low blood glucose is caused by an imbalance between the factors that raise and decrease blood glucose levels. Those causing an increase in blood glucose include food and counter-regulatory hormones (glucagon, adrenaline and cortisol) and those causing a decrease include insulin or oral medication and physical activity.

With new technologies, such as flash glucose monitoring systems and continuous glucose monitors (CGMs), we get a clearer picture of what the blood glucose levels are doing over a 24-hour period.

This is compared to the traditional self-blood glucose monitoring (SBGM) system whereby with a prick of the finger you get your blood glucose reading of that given moment. In the case of SBGM, if you test your blood glucose and see that your levels are low, you have no idea where they may be going from there.

With CGMs and flash glucose monitoring systems, we can see in the form of an arrow which way the glucose is trending. And, with some of the newer CGMs, the rate at which it is trending up or down.

Common reasons for a low blood glucose reading:

  • Delayed or skipped meal.
  • Eating too little carbohydrates at a meal.
  • Overestimated the carbohydrates eaten, if using carb counting.
  • If you have exercised or been physically active.
  • Taken too much insulin in relation to what your body needs.
  • New injection site, therefore, avoiding lumpy tissue where insulin absorption is unpredictable.
  • Consuming alcohol.

How to treat hypoglycaemia?

This will depend on various factors, such as the rate at which the blood glucose is decreasing by, how much active or unused insulin is on-board, and when you last ate something carbohydrate-based.

Active insulin is the time that insulin remains working in your body, it refers to a bolus injection and this is usually 3-4 hours.

Having pure glucose is the preferred treatment for hypoglycaemia. However, any carbohydrates that contains glucose will raise blood glucose levels.

It is important to test blood glucose first, treat with the correct amount of rapid-acting carbohydrates, wait 15 minutes and then retest your blood glucose. If you are still not feeling better and your blood glucose has not risen, then you should repeat with the same amount of glucose. 0,3g of glucose/kg will increase the blood glucose reading by approximately 2 mmol/L.

Studies have shown that 15g of glucose is required to get an increase in blood glucose of approximately 2,1mmol/L within 20 minutes.

Examples of 15g of carbohydrate for the treatment of mild to moderate hypoglycaemia:

  • 15g of glucose in the form of glucose or dextrose tablets.
  • 15ml (3 teaspoons) of sugar.
  • 150ml of regular soft drinks.
  • 15ml (1 tablespoon) of honey.

Danger of over-treating hypoglycaemia

Over-treating hypoglycaemia should be avoided as much as possible because this can lead to rebound hyperglycaemia (high blood glucose) and weight gain.

To fix a low blood glucose reading you need time, not more food. It is important to note that the liver is also responsible for glucose output and rebound hyperglycaemia.

Glucose has a quicker effect on the blood glucose compared to other types of carbohydrates. You should avoid food and drinks containing fat, such as chocolates, biscuits or milk. The fat in these food items will delay digestion in the stomach and the glucose will therefore take longer to reach the bloodstream.

Fructose (the fruit sugar naturally found in fruits) is absorbed more slowly from the intestine and is not as effective as glucose in raising blood glucose levels.

Why can’t hypoglycaemia be treated with ‘real food’?

Treating hypoglycaemia with ‘real food’, for example, a banana will completely depend on the situation at hand. With the use of CGMs, we may be able to use ‘real food’ more frequently to treat a lower blood glucose reading before reaching the hypoglycaemic range.

With SBGM, we are limited because we only have that one reading for that specific time and no other information to tell us where we are going. Because of this, eating something like a banana (without any active insulin), may cause an undesirable rise in blood glucose.

Diabetes is an extremely unpredictable disease and it may be impossible to prevent all future hypoglycaemic episodes. It is important to evaluate your current diabetes management plan with your endocrinologist, diabetes nurse educator and registered dietitian to reduce and prevent large fluctuations in blood glucose readings.


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  2. Yale JF, Paty B, Senior PA. 2018 Clinical Practice Guidelines: Hypoglycemia. Can J Diabetes 2018; 42: 104 – 108.
  3. Barnard K, Thomas S, Royale P, Noyes K, Waugh N. Fear of Hypoglycemia in parents of young children with type 1 diabetes. BMC Pediatrics 2010, 10:50.
  4. Hanas, R., Type 1 Diabetes in children, adolescents and young adults. 6th Class Publishing: Bridgwater, 2015.


Jessica Oosthuizen is a registered dietitian and works in private practice at the Wits Donald Gordan Medical Centre. Being a Type 1 diabetic herself, since the age of 13, Jessica has a special interest in the nutritional management of children and adults with diabetes. She also has a key interest in weight management and eating disorders.