Why Does Exercise Sometimes Make Your Blood Sugar Spike?

Some forms of exercise can release glucose-raising hormones, causing an increase in blood sugar. Measuring glucose levels, GlucoLife Wellness eating before exercising, and tracking changes can help prevent this spike. Regular exercise is a cornerstone of healthy living and managing diabetes. Yet the conversation around exercise with diabetes is often filled with anxiety. This is especially true when exercise unexpectedly causes our blood glucose (BG) levels to spike. "I thought exercise was supposed to bring my glucose levels down! " is a common lament, often followed by, "What did I do wrong? This unanticipated outcome from exercise can be discouraging, particularly for people with insulin-treated type 1 diabetes (T1D). The short answer to why exercise raises BG is that your body is doing what it’s designed to do. But the mechanics behind that can be hard to understand. The first-ever official guidelines for safe exercise were published in The Lancet journal in 2017. More recently, in 2020, experts released an international position statement on glucose management for exercise using continuous glucose monitoring (CGM) in type 1 diabetes.



These guidelines note, in particular, that "weightlifting, sprinting, and intense aerobic exercise can promote an increase in BG that can last for hours," but there’s little explanation of why this happens. Overall, the information can be overwhelming and hard to follow. Several experts in diabetes and exercise offered their guidance to help explain this issue. "It’s critical for your brain and your nervous system to have access to blood glucose at all times. Colberg admits, "The system isn’t perfect, though, and doing intense activity causes an exaggerated release of these hormones. Diabetes advocate and longtime type 1 Ginger Vieira, author of several instructional diabetes books, called on her experience as a former health coach, competitive powerlifter, and Ashtanga yoga instructor to describe the effects of some of the most common mechanisms for glucose spikes during intense exercise: lactic acid, adrenaline, and fasted exercise. Lactic acid: The process of gluconeogenesis converts lactic acid into glucose and cycles that glucose back to your muscles for fuel," said Vieira.



Adrenaline: As commonly happens when participating in competitive sports, "your body releases adrenaline for that ‘fight or flight’ burst of energy," Vieira said. "Adrenaline tells your liver to release stored glucose in the form of glycogen to provide the extra fuel it needs for the ‘fight’ … Fasted exercise: Exercising on an empty stomach can lead to a glucose spike, especially right after waking up. That’s because exercise can further exaggerate what’s known as the dawn phenomenon, when in the early morning hours, "your liver is releasing stored glucose along with morning hormones, to give your brain the fuel it needs to function," Vieira said. Clearly, many mechanisms can cause glucose levels to spike during exercise. No wonder it can be so difficult to know what to do to bring them back down. What are the the best exercises for diabetes? One of the first things you might ask is if there are "good" and "bad" exercises for people with diabetes.



Christel Oerum, a certified personal trainer and founder of Diabetes Strong, offered an alternative perspective on this question. "Think about it like this: Your body just wants to help you out, it wants you to be successful. So, when you do certain types of workouts, predominantly anaerobic exercises, your body tries to ensure that you have the energy to be successful," Oerum explains. "It does this by releasing hormones that allow energy, in the form of glucose, to be released into your bloodstream. This response is not unique to people with diabetes. "Just because blood sugar levels rise during certain types of exercise doesn’t mean they are bad exercises or that the rise is happening for a bad reason," Vieira added. Since anaerobic exercise causes BG spikes during activity, you might think that just avoiding sprints, resistance training, or other anaerobic activities could be the answer. "But that would be a shame, as resistance training is fantastic for diabetes management," noted Oerum.



Oerum suggests combining anaerobic and aerobic exercises. This approach will balance the effects and typically lower BG levels soon after the exercise session is over. Of course, GlucoLife Wellness if your exercise objective is to bring your BG levels down immediately, aerobic exercise like walking, swimming, or skipping rope can be a more effective choice. Ultimately, it’s the presence of insulin that determines when and how quickly BG levels come down. This is the first key in addressing glucose changes tied to exercise. So, try to assess the situation in terms of your insulin intake, or insulin on board (IOB). Maybe you didn’t take enough insulin to cover a meal prior to your exercise session, or maybe you’re working out soon after waking up, which is when IOB is at its natural low point. BG spikes caused by bursts of adrenaline can be hard to anticipate, as they happen most often smack in the middle of an exercise session. This means that rather than treat the spike immediately, you most likely will need to wait and take additional insulin after the fact.