Hyperglycemia: Complications & Consequences

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson we'll be exploring what happens to the body during hyperglycemia. Here, you'll find out how hyperglycemia relates to diabetes and its consequences for different organ systems, such as the kidney, liver and brain.

What Is Hyperglycemia?

Although sugar has gotten a bad rap lately, it's actually completely necessary for our bodies. Sugar isn't just in soda - fruits, vegetables, rice, and other grains are all made of carbohydrates, which are long chains of individual sugars. Sugars are needed for our body to make energy to do all our daily functions, from running a race to simply breathing while you sleep. In fact, your brain only runs on a specific sugar called glucose. It can't use fat or protein for energy like the rest of your body, so you need to keep a healthy amount of glucose in your diet through carbohydrate-rich foods, like fruits.

However, as we know, too much of a good thing can actually be bad. The body always wants to be in balance, or homeostasis. Too much or too little of a nutrient can wreak havoc on our organ systems, and sugar is no different. If you have too little sugar in your body, your brain won't be able to do its job and you can even pass out. But too much sugar creates a condition called hyperglycemia, where the amount of glucose in your blood, or blood glucose level, is too high. Hyperglycemia might seem like a mouthful, so let's break it down. The prefix 'hyper' means high and 'glycemia' refers to blood glucose, so hyperglycemia is a high blood glucose level.

The most common cause of hyperglycemia is diabetes. Diabetic patients either don't make enough of a molecule called insulin, or no longer respond to it. Insulin causes cells to take up glucose from the blood, lowering blood glucose levels. So without insulin, glucose stays in the blood, leading to hyperglycemia.

When the body does not respond to insulin, hyperglycemia results

Consequences and Symptoms

So what happens if you develop hyperglycemia? How could you diagnose a patient with hyperglycemia? One of the first signs is increased thirst, with frequent urination. Your patient will feel like they just can't get enough water. They also would complain of having to urinate often because the body is trying to get rid of the excess glucose through the kidney.

This leads to another interesting symptom. Urine from a person with hyperglycemia will smell, and actually taste, sweet. In the 1600s, long before blood or urine testing for glucose was available, doctors actually tasted patients' urine to diagnose hyperglycemia! That isn't recommended now for medical professionals, since other diagnostics are available to test blood glucose levels.


Unfortunately, the consequences of untreated hyperglycemia aren't limited to just sweet urine. Let's look at how untreated hyperglycemia can affect the body.

Diabetic Neuropathy

A diabetic patient comes to you, complaining of tingling in their hands and feet. What's going on with this patient?

Nerves connect our brains with our bodies. During diabetes, hyperglycemia causes blood vessels to become leaky. This might not seem like a big deal, but our blood has lots of proteins and other molecules that need to be tightly controlled. If the blood vessels leak, these molecules seep into surrounding tissue, including our nerves. The molecules that leak out of the blood cause damage to the nerves, preventing them from sending signals to our extremities, which results in tingling in the hands and feet. This condition is called diabetic neuropathy, referring to the death of nerve tissue.

However, consequences can get more severe. Damage to the nerves prevents the brain from talking to the body and can cause major problems like organ dysfunction and even paralysis, if left untreated.

Diabetic Retinopathy

Imagine looking at two children playing in the park. Now, take a look at what this scene looks like for a patient with diabetic retinopathy.

Point of view of a patient with diabetic retinopathy
diabetic retinopathy

During diabetic retinopathy, blood vessels grow out of control in the retina. Your retina is the tissue in the back of the eye, filled with nerves needed to interpret visual stimuli, allowing us to see. When excess blood vessels grow into the retina, the retina can't do its job, and blindness can occur. Patients might experience tunnel vision, black spots in their vision, blurry vision, or even total blindness depending on how far the disease progresses.

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