How Does Blood Sugar Impact my Energy Levels?

blood sugar and energy levels

Blood sugar is highly correlated with energy levels. It is largely responsible for the feeling of sleepiness that we experience after big meals (like Thanksgiving dinner). It is also behind the energy slump that we may face in the afternoon.  Many of us can intuitively feel changes in energy when we have not eaten for an extended period and our blood sugar drops.

Individuals with either type 1 or type 2 diabetes are especially susceptible to changes in energy levels, as they have a significantly higher rate of fatigue than healthy individuals. These episodes of fatigue coincide with glucose excursions. Fatigue is so commonly associated with type 2 diabetes that it is referred to as “diabetes fatigue.”  Let us take a dive into the science to show how blood sugar is correlated with energy levels and how we can sustain our energy throughout the day. 

How does high blood sugar impact my energy?

blood sugar and energy levels

High blood sugar is associated with fatigue.  This fact may sound counterintuitive since processed foods, like candy, spike our blood sugar and we associate this “blood sugar rush” with hyperactivity. However, too much sugar can put us into a hyperglycemic state. Hyperglycemia is when our blood sugar rises over 7.8 mmol/l (140 mg/dl). This sudden increase in sugar could be due to consuming a high volume of refined carbohydrates, a lack of insulin, or insulin not working effectively. The result is an accumulation of glucose in the bloodstream without sufficiently functioning insulin to pull it out of circulation.  Research has shown that dramatic increases in blood sugar (300 mg/dL) induce a significant decrease in energy levels and deteriorated mood state (as well as diminished working memory, attention, and processing speed with increased anxiety). 

How does low blood sugar impact my energy? 

blood sugar and energy

Low blood sugar can occur for a variety of reasons. Glucose levels can drop overnight, we can experience low blood sugar as a result of extended high-intensity exercise, or through a process called reactive hypoglycemia.  Reactive hypoglycemia occurs as a result of consuming high-carbohydrate foods. These foods cause a dramatic increase in blood sugar, which prompts a large release of insulin. This insulin overcorrects and causes a fast blood sugar crash, leaving us feeling fatigued and tired shortly after eating. The good news is, we can reduce the likelihood of experiencing reactive hypoglycemia. When we control our blood sugar we diminish the post-meal spikes and subsequent reactive hypoglycemia. In this way, we can help to maintain stable energy levels and avoid the hypoglycemia that zaps our energy.

Low blood sugar can also occur overnight. Low overnight glucose levels (42 to 59 mg/dL) are associated with lower energy levels. Nighttime hypoglycemia can occur when a person with diabetes exercises close to bedtime or when alcohol is consumed in the evening.  

Low blood sugar can also be caused by performing high-intensity exercise (>60% VO2 max) for durations exceeding 90 minutes without refueling. When we perform high-intensity exercise, such as repeated sprints, intervals, or sustained all-out efforts we utilize carbohydrates as the primary energy source. If we continue to exercise at this intensity we can burn through the glucose that is circulating in our bloodstream as well as our stored glucose (aka glycogen) that is stashed in our liver and muscles. After we utilize all of our glucose and glycogen, muscle cells won’t be able to produce energy (ATP) rapidly enough to maintain exercise intensity, and we “bonk.” Not only will this depletion of blood sugar hinder athletic performance, but it will also cause us to feel fatigued and lack energy.

What about dramatic changes in blood sugar?

sugar level feel good zone

So far, we have learned that high glucose causes fatigue and low glucose causes fatigue.  Guess what, these swings also zap our energy. When we have large swings in blood sugar it increases the amount of oxidative stress. Oxidative stress is associated with chronic fatigue. This is just another way in which glucose dysregulation is associated with decreased energy levels, fatigue, and decreased alertness. 

How can we improve energy levels with blood sugar management?

exercise for blood sugar management

When we talk about blood sugar and energy we are not referring to the spike in energy that would normally be associated with an energy drink. Most energy drinks contain caffeine or another stimulant that boosts the adrenal system, which can lead to jitters and a delayed energy crash. Instead, when we control our blood sugar, we prolong our baseline energy levels by reducing the occurrence of energy drops. In this way, we can help to sustain our energy levels throughout the day.

Ways in which we can manage our blood sugar (and thus energy levels) include exercise, proper nutrition, tools like GOOD IDEA, and meal sequencing.  Exercise can help to improve our insulin sensitivity and more effectively transport glucose out of the bloodstream and into the cells to be used as fuel.  


Practicing healthy nutritional choices is likely the most effective way that we can control our blood sugar. By choosing foods that do not spike our blood sugar we can reduce the extreme highs and lows that zap our energy. Start by swapping out highly-processed foods and sugary drinks for high-protein and low-sugar options. Individuals who choose to use a continuous glucose monitor (cgm) can test specific foods and monitor the glucose response to identify foods that do not cause a blood sugar spike. In this way, we can make more informed food choices to appropriately control blood sugar. 

Another way in which we can work to control blood sugar is by using a functional beverage like GOOD IDEA.  GOOD IDEA, a beverage backed by science, has been shown to reduce post-meal blood sugar by at least 20%. This can become a great option to help regulate blood sugar when we are around unfamiliar foods or out with friends/family. 

Lastly, meal sequencing is a strategy in which we can eat our food in a certain order to activate the appropriate hormones and peptides to effectively reduce post-meal blood sugar. When we consume fiber with protein and/or fat first and save our carbohydrates until the end of the meal, we can minimize the post-prandial glucose spikes and stabilize energy levels for longer.



 Author: Dr. Colleen Gulick