What Happens If Sugar Is Given During an Episode of Hyperglycemia

First-aid manuals say to give sugar to any person with diabetes exhibiting signs of confusion. But you wouldn't know without blood testing whether they were having an episode of low blood sugar (hypoglycemia) or high blood sugar (hyperglycemia), as the symptoms are quite similar. Giving sugar will help the person with low blood sugar get through their crisis. But what happens if you give someone with high blood sugar more sugar?

Ma checking blood sugar with a small device
Mark Hatfield / Getty Images

The answer is that in the short term, nothing happens for the person with hyperglycemia—the sugar will not make the condition worse. However, that doesn't mean high blood sugar isn't a problem. Learning why this is the case starts with understanding how your body gets energy and the difference between what is happening during episodes of low blood sugar and high blood sugar.

Alternative Fuels: Running on Sugar or on Fat

The body basically runs on two different fuels: fat and sugar. The premium fuel is sugar—it burns cleaner and much more efficiently. Every carbohydrate and protein you eat is eventually broken down into sugar for your cells to use as fuel.

However, your body is a versatile engine. It can also use fat as a fuel. It's not clean burning—kind of like the difference between high octane racing gas and coal—but it gets the job done in a pinch.

Not all cells in your body are capable of using alternative fuel. Some of the cells are high-performance, and only the premium fuel will do. The brain is just such an elite machine. Brain cells cannot burn fat for energy.

When the bloodstream runs low on sugar, the body tries to save it for the brain. When the blood sugar gets too low, the brain starts to sputter—and the victim becomes dizzy, confused, and weak. Nothing will work other than sugar, the premium, high-octane racing fuel for the body.

High blood sugar (hyperglycemia) is a different mechanical problem entirely and has a different cause and requires different treatment. Sugar builds up in the bloodstream because there isn't enough insulin in there to use it. For most cells other than the brain, insulin is the fuel pump. It moves sugar from the bloodstream into the cells by binding with the sugar. Without insulin, sugar can't get into most types of cells.

When the insulin production facility—the pancreas—breaks down, there's not enough insulin to use sugar. The body switches to the backup plan, which is to burn fat instead. All except for the brain, which is still happily running on sugar (of which there is now plenty because the rest of the body isn't using it).

High Blood Sugar and the Brain

People with high blood sugar can get confused, weak, and dizzy—just like people experiencing low blood sugar—but for a completely different reason. It's not the lack of fuel for the brain; it's the pollution that comes from burning fat. When the rest of the body is burning fat, byproducts known as ketones are released into the bloodstream. Ketones are very acidic and the brain is finicky; it can't work in an environment with too much acid and begins to malfunction. It's a dangerous condition known as diabetic ketoacidosis (DKA).

Note that diabetic ketoacidosis differs from nutritional ketosis, which is the aim of the ketogenic or "keto" diet. In the keto diet, levels of ketones are much lower than in DKA.

It takes an excessive amount of ketones in the blood to affect the brain, so high blood sugar levels don't often affect the brain for days—sometimes weeks. In that time, the actual sugar levels can go up or down. It's the lack of insulin and the burning of fat rather than the presence of extra sugar that causes the problem.

So, giving sugar to people with high blood sugar isn't going to help—they already have too much. But it's not going to hurt, either.

Giving Sugar Saves Those With Low Blood Sugar

On the other hand, giving sugar to someone with low blood sugar could save a life. In most cases when a person known to have diabetes becomes confused, weak, or dizzy, the cause is low blood sugar and the person will get better after eating sugar. Their blood glucose level will rise and their brain will again have fuel to function.

The most important thing is to recognize when giving sugar doesn't help. In that case, you'll need to get the patient to a doctor as soon as possible or call 911.

2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Schönfeld P, Reiser G. Why does brain metabolism not favor burning of fatty acids to provide energy? Reflections on disadvantages of the use of free fatty acids as fuel for brainJ Cereb Blood Flow Metab. 2013;33(10):1493–1499. doi:10.1038/jcbfm.2013.128

  2. American Diabetes Association. Diabetic Ketoacidosis.

Additional Reading

By Rod Brouhard, EMT-P
Rod Brouhard is an emergency medical technician paramedic (EMT-P), journalist, educator, and advocate for emergency medical service providers and patients.