What you need to know about blood sugar and the brain

Diabetes, particularly when not properly managed, can damage many of the body’s organs – the heart, the kidneys, the skin, and the liver, to name a few. But did you know that out-of-control blood sugar can also impact the brain?

It’s true, and what happens to the brain when blood sugar spikes or drops can be frightening because it can change the way you think, feel, problem solve and understand the world around you.

Diabetes and the Brain

Your brain runs on blood sugar. If this comes as a surprise to you, here’s the explanation. The brain is the body’s command center. It’s made up of countless nerve cells that need to be energized to keep your body functioning properly. Even when you’re sleeping, the brain is still working, so suffice it to say that the cells inside your brain have a lot on their plate and are always working overtime.

In fact, your brain is the most energy-demanding organ in your body. How demanding? Get this. Your brain uses half of all the sugar energy in your body to make sure you function properly. Because the brain is so dependent on blood sugar, diabetes can throw your command center out of whack with its high and low blood sugar episodes.

Just as uncontrolled blood sugar can lead to nerve damage in the feet and eyes, it can also damage the nerves in the brain, as well as the blood vessels that feed both oxygen and glucose to the brain. When this happens, a person can experience brain fog.

What is Brain Fog?

Brain fog isn’t really a single condition. It’s used to describe the many impairments that can result when the brain is negatively impacted by too much or too little blood sugar. Brain fog can mean:

– A decreased ability to concentrate

– Problems remembering even recent events

– Irritability and mood swings

– Feelings of anxiety or depression

– General confusion

– Issues with learning

– Mental fuzziness

Hyperglycemia and Brain Fog

You might think that because the brain uses so much sugar to energize its cells, the more, the merrier. Wouldn’t the brain work even better when blood sugar is high and there’s theoretically more food for thought? This just isn’t true. High blood sugar over time can damage the blood vessels that carry oxygen-rich blood to the brain. Without this enriched blood, some brain cells can die off, a condition known as “brain atrophy” and quickly cause a person to have difficulty thinking and remembering clearly. Eventually, this can lead to vascular dementia and even Alzheimer’s Disease. The frightening part of hyperglycemia and the brain is that the symptoms of high blood sugar don’t often present themselves immediately. So, the brain is often being negatively affected long before a person with diabetes realizes there’s a problem.

Hypoglycemia and Brain Fog

According to the Centers for Disease Control and Prevention, hypoglycemia occurs when blood sugar levels drop below 70 mg/dL. If left untreated, hypoglycemia can be very dangerous because the brain does not get enough blood sugar to feed itself and gradually begins to shut down. However, unlike hyperglycemia, when a low comes on the signs are usually immediately apparent and include dizziness, shakiness, irritability/mood swings, confusion, even difficulty walking or talking.

It's unclear if low blood-sugar causes long-term effects on the brain, but some studies indicate that substantial and frequent dips in blood sugar may be connected to problems with depression, memory loss, and attention span.

Signs of Brain Fog

We’ve already touched on some of them in general, but what follows is a more specific list of signs. Remember, brain fog is not a single condition but rather a term used to describe many issues related to the brain and inconsistencies in blood sugar. Not everyone will experience the same symptoms, nor will everyone experience them with the same severity. But if you have diabetes and feel any of the following, it could be a signal that a blood sugar high or low is causing you to have brain fog:

– Unusually intense fatigue

– Problems finding the right words

– Inability to follow a conversation

– Unable to concentrate on the job at hand

– Feeling as if you’re moving in slow motion

– Trouble processing information

– Mood swings

– Feeling disconnected from those around you

– Dizziness/equilibrium issues

Can You Prevent Brain Fog?

Yes! The best way to prevent diabetes-related brain fog is by keeping your blood sugar levels within the target range dictated by your physician. For most people this is between 80 and 130 mg/dL before meals and less than 180 mg/dL two hours after a meal. Your individual target range, however, may vary depending on your specific condition and diabetes management program.

Regardless, by keeping blood sugar within your target range, you minimize the risk of highs and lows impacting brain function. So:

  1. Test your blood sugar daily using a glucose meter and test strips, or a doctor-prescribed continuous glucose monitoring (CGM) device.
  1. Adhere to your doctor-prescribed diabetes medication and treatment plan, including any insulin injections by syringe or pen.
  1. Do your best to keep blood sugar in check by eating a diabetes-healthy diet that’s low in saturated fats and sugars, but high in fiber and nutrients.
  1. Get in about 150 minutes of physical activity each week in accordance with the recommendations of the American Diabetes Association (ADA).
  1. Make sure you get adequate sleep, at least 6-8 hours per night. Poor sleeping patterns can exacerbate any issues you experience with concentration and clarity.

Treating Brain Fog

If you do experience diabetes-related brain fog, it’s time to see your physician. It very well may be all you need is a simple adjustment to your medication and treatment program. You might even be able to remedy the problem with some dietary and lifestyle changes.

But remember it is important to treat and solve the blood sugar highs and lows that lead to brain fog because left untreated things will get worse. Plus, high and lows also contribute to other diabetes-related complications, including cardiovascular disease, kidney damage, neuropathy, increased risk of infection and more.

So, if you experience any of the symptoms of brain fog, please see your physician right away.


We hope you found this post informative and insightful. At Diabetic Warehouse, we’re committed to helping those with diabetes control blood sugar and avoid diabetes-related complications with a complete selection of testing and treatment supplies at prices up to 65% less than those found at most pharmacies and suppliers.

Diabetic Warehouse is a trusted supplier of diabetes care products and accessories. For more information and to explore a complete range of products, including glucose meters and test strips, insulin syringes, pen needles, continuous glucose monitoring systems, and more, visit