The Connection Between Blood Sugar and Mood

The Connection Between Blood Sugar and Mood



“Since our brain primarily runs on glucose, having high or low blood sugar can significantly impact our mood. Low blood sugar can cause anxiety, confusion, and irritability. High blood sugar can induce feelings of fatigue, anger, or sadness. Managing our blood sugar can go a long way towards helping to reduce those “hangry” feelings and improve our mood.”


blood sugar and mood

Did you ever notice how you can get irritable or “hangry” when you are hungry?  Do you feel jittery and anxious after a late-night candy binge?  You can thank your blood sugar and brain for these mood changes. The brain is the most energy-demanding organ in the body.  It is composed of a network of nerve cells (neurons) that are constantly working.  Just as our muscles need energy to exercise, our brain also relies on a constant supply of fuel in order to sustain a high level of function. Since the primary source of fuel for the brain is glucose, changes in blood sugar concentrations significantly impact cognitive performance and mood. This need is especially evident in high-stress environments or work situations where there is high cognitive demand.

Glucose and the brain

The brain’s primary fuel source is glucose through the generation of adenosine triphosphate (ATP) (ketones can also be used to power cognitive functions under certain metabolic conditions).  However, the brain lacks the ability to store glucose.  Thus, when glucose is not available in circulation the brain is unable to use it for fuel.  This is problematic for individuals that are not metabolically flexible. They rely on a continuous supply of exogenous glucose to fuel physical activity, leaving minimal glucose left to power the brain.  For these individuals, when the level of circulating blood glucose falls, the rate of cerebral glucose metabolism will decline as well.  This can result in changes in mood as well as cognitive performance.

How does blood sugar change throughout the day?

Your morning run, an afternoon snack, stress, or medications can all alter blood glucose concentration.  Blood sugar rises after a meal. A higher carbohydrate meal will induce larger spikes in blood sugar than a lower carbohydrate meal or a meal that contains protein. Exercise, particularly high-intensity exercise (>60% VO2max), will utilize the glucose in the bloodstream as fuel for muscles, effectively decreasing the amount in circulation.  Stress can also increase blood sugar via the release of two hormones (cortisol and epinephrine).  Some medications can also have a powerful impact on blood glucose.

How does low blood sugar impact our mood?

low blood sugar and mood

Hypoglycemia (blood sugar less than approximately 70 mg/dL) can increase feelings of anxiety and confusion. This can make it challenging to stay on task and focus.  Low blood glucose leads to a loss of mental focus and feelings of weakness, like the mental fatigue we experience the hour before our lunch break.  Signs of low blood glucose are dizziness, shakiness, headache, and irritability.  Clearly, none of these symptoms are desirable but many of us frequently experience them (remember the last time you were “hangry”?). 

How does this happen?

When your blood sugar drops, your body tries to restore your blood sugar to its normal levels. It increases the release of epinephrine, a hormone commonly called adrenaline, that signals the liver to make more glucose.  This adrenaline also increases your heart rate, can cause sweaty palms, and makes you feel cranky or anxious.  If the adrenaline does not cause your blood sugar to rise enough, your body goes to plan B and releases cortisol (a stress hormone).  The combination of adrenaline and cortisol can cause the symptoms of anxiety, the “hangry” feeling we get before meals, and sugar cravings.  

How does high blood sugar impact our mood?

blood sugar and mood

Hyperglycemia (high blood sugar) for non-diabetic individuals occurs when blood glucose levels rise to more than 180 mg/dL one to two hours after a meal or 125 mg/dL when fasted. This is a very large spike for a non-diabetic and can be caused by a high sugar intake, some medications (steroids and diuretics), major illness, injury, or chronic diseases. In the short term, hyperglycemia can induce feelings of fatigue, anger, or sadness. A study that examined the effects of acute hyperglycemia on cognitive function in individuals with type 2 diabetes found that cognitive function was impaired and mood state deteriorated during acute hyperglycemia.  Chronically high blood sugar is problematic as well. Persistently high blood sugar (due to poorly managed diabetes) may also worsen depressive feelings or increase anger.

When hyperglycemia occurs, the sudden rise in blood sugar triggers the body’s release of insulin. Insulin release is a healthy response that initiates rapid glucose uptake by tissues, which either stores the glucose as glycogen or uses it for energy production. An overproduction of insulin, however, causes a rapid decrease in blood sugar below normal levels (reactive hypoglycemia).  This reactive hypoglycemia can impact mood by making it difficult for us to concentrate, anxious, and irritated.

How low is too low?

Blood sugar is incredibly individualized. Most people feel symptoms of low blood sugar when their blood glucose drops below 70 mg/dL.  For non-diabetics, low blood sugar can be caused by some medications, drinking too much alcohol, or eating lots of sugary foods. For individuals with diabetes, taking too much insulin, skipping meals, eating less than normal, or exercising more than normal can all decrease blood sugar. When it comes to improving our mood, reducing dramatic spikes and drops in blood sugar is most important.

How can we maintain stable blood sugar?

Exercise, food choice, food timing, stress, sleep, and hormone levels are just a few of the factors that impact our blood sugar. While living a stress-free life with healthy food and time to exercise and sleep sounds wonderful, it simply isn’t realistic for many of us. Luckily, we do not have to be perfect in each of these categories in order to have blood sugar levels that stay within a healthy range. While we all try to minimize stress, it is likely the variable that is least within our control. So, focusing on food is usually a good place to start since it requires less time commitment, is easily modified, and has the potential to cause the greatest spikes in blood sugar and, thus, harm our health. Start by swapping simple carbohydrates (processed foods and candy) for foods higher in protein. Simple carbohydrates cause a dramatic spike, then dive in blood sugar. By minimizing the intake of these foods we can stabilize our blood sugar, reduce cravings, and improve our mood. Protein, on the other hand, does not cause dramatic increases in blood sugar, it helps us to feel full for a longer period of time, and won’t induce a blood sugar “crash” that has you feeling irritable and moody.

good idea reduces post meal blood sugar

If you are in an environment where the food choice is out of your control or you are about to eat a meal higher in carbohydrates, drink 1/3 of a can of GOOD IDEA before your meal and finish it with your meal.  This has been shown in multiple studies to reduce post-meal blood sugar by at least 20%. This can help to ward off the mood alternations that accompany extreme glucose spikes and dips.

Another simple change that can be made to help improve blood sugar management is eating your food in a specific order. While this may seem odd, the order in which your body receives food dictates how it responds. Consuming vegetables first (like a starter salad), protein and fat second, and starches/sweets last can help to reduce blood sugar spikes. For most people, the largest adjustment is saving bread and sweets to last. We know it is hard to pass up on those pre-meal breadsticks but your blood sugar (and mood) will thank you later.

When we swap simple carbohydrates for protein-rich food, use GOOD IDEA with a meal, or eat our food in a specific order we help to avoid the fatigue that accompanies high blood sugar and the irritability that happens with low blood sugar. As an added bonus, managing our blood sugar helps to improve our metabolic health, which should make us feel proud and boost our mood even further.


Author: Dr. Colleen Gulick