Regular exercise can help with weight management, lower insulin resistance, and improve cardiovascular health. However, if you monitor your blood sugar continuously (CGM), you might see blood sugar spikes after working out. Because you are trying to improve your health, this can be frustrating because it seems ineffective. It’s important to keep in mind that blood sugar spikes after exercise typically do not result in weight gain because the blood sugar that is released into the bloodstream during exercise is typically used by the muscles or converted to glycogen.

Cortisol and adrenaline are stress hormones that are released along with an increase in exercise intensity. These hormones raise blood sugar levels. This reaction makes sure that the body’s cells have enough energy. Insulin moves blood sugar from the blood to muscle cells as cortisol raises blood sugar levels to satisfy the increased demand for energy.

If you exercise at a low to moderate intensity and are not insulin resistant, blood sugar will enter muscle cells roughly at the same rate that it is produced. The intensity of your exercise will determine the amount of cortisol and adrenaline released and the rate at which blood sugar enters the muscle cells. Exercise-related blood glucose elevations can be caused by strenuous activity, an inability to produce insulin or insulin resistance.

You can learn more about the causes of blood sugar spikes after exercise in the sections below.

Why is My Blood Sugar High After Exercise？

Your body is functioning as it was intended to, to put it succinctly. But it can be challenging to comprehend how that works. There are a number of reasons for this, to put it briefly.

Adrenaline Acts

Using your muscles helps burn blood sugar and improves the way insulin works. Because of this, blood glucose levels typically decrease while exercising. But you might see blood glucose go up after exercise, too. You release stress hormones (like adrenaline) after engaging in certain exercises like heavy weightlifting, sprints, and competitive sports. By encouraging your liver to release blood sugar, adrenaline increases blood glucose levels.

The food you consume before or during exercise may also cause your blood sugar to increase. Eat too many carbs before exercising, and your sweat session may not be enough to keep your blood glucose within your goal range.

Aerobic Metabolism

Blood sugar can completely break down into carbon dioxide and water in the presence of oxygen, producing a net of 36 ATP. blood sugar, pyruvic acid, and fatty acids can all be broken down by aerobic metabolism. The most effective way to make energy is through aerobic metabolism. 95% of the ATP required by muscle cells is produced by aerobic metabolism, whether at rest or during moderate exercise.⁴

Skeletal muscle preferentially burns fatty acids using aerobic metabolism while at rest and during low-intensity exercise. Fatty acid metabolism requires oxygen. Skeletal muscle switches to using blood sugar for energy as exercise intensity increases because glycolysis is a quicker process that doesn’t require oxygen.

Glucose Metabolism

Your blood sugar rises when you eat a carbohydrate-rich meal. A healthy pancreas produces more insulin as a result. Insulin opens transporters in cell membranes, allowing blood sugar to enter body cells to be used for energy. Muscle and liver cells store extra blood sugar as glycogen.

The need for blood sugar rises during physical activity. Glycogen is converted to blood sugar by the enzyme glycogen phosphorylase. Muscle glycogen supplies muscles with energy, while liver glycogen provides energy to other body organs, especially the brain and spinal cord.

At rest, insulin shuttles blood sugar into cells, especially muscle, and liver, where it is stored as glycogen. Blood sugar becomes available for muscle and other body cells when glycogen is broken down to release it in response to rising energy demands.

Lactic Acid

The process of gluconeogenesis converts lactic acid into blood sugar and cycles that blood sugar back to your muscles for fuel,” said Vieira. “This is how your body fuels your muscles when you’re exerting too much effort for your body to circulate oxygen and blood sugar to your cells as it would during general aerobic [cardio] exercise.”

How to Control Blood Sugar Spikes After Exercise

In the end, when and how quickly BG levels fall depends on the presence of insulin.

So, try to assess the situation in terms of your insulin intake, or insulin on board (Perhaps you didn’t take enough insulin to cover a meal before your workout, or perhaps you’re exercising right after waking up when IOB is naturally at its lowest 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. As a result, you will probably need to wait and administer additional insulin after the spike has passed rather than treat it right away. Additionally, more insulin is required when the increase is due to fast exercise. There will be a small amount of extra insulin required, but not enough to cause a hypoglycemic episode during or after exercise.

Unfortunately, there are no hard and fast rules for making these insulin-dosing adjustments. Every circumstance and every person will require a unique response. Choosing the best course of action for you should be discussed with your medical team.

You can also experiment with your own ideal “starting glucose level” before kicking off exercise. The 2017 guidelines give the general recommendations of “at-target” levels of 126 to 180 mg/dL, and consuming 10 to 20 grams of fast-acting glucose before getting started. You’ll need to keep an eye on your own experience to figure out what works best for you. You will hopefully notice a mental shift away from being frustrated and disappointed towards appreciating what you can do in response once you understand why BG levels spike during exercise and accept that this is not necessarily a bad thing.

There is no one-size-fits-all advice, but you can gradually develop a workout routine that incorporates modest doses of insulin and glucose that keeps your blood sugar levels under control.

Summary

All diabetics should engage in regular physical activity. Most forms of aerobic/cardiovascular exercise will lower your blood sugar levels, while activities such as high-intensity training and weight lifting will raise them. Controlling blood sugar levels with any form of exercise is doable once you have an understanding of your unique patterns (regular blood sugar checks and keeping an exercise journal will help with this).

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