Running With Type 1 Diabetes: What You Need to Know


Regular exercise has health benefits for those with type 1 diabetes, including increased cardiovascular fitness, greater muscle strength, and improved insulin sensitivity. While physical activity is very important in managing type 1 diabetes, understanding exactly how it impacts blood sugars can be difficult and worrisome, particularly for those who are newly diagnosed.


Typically, exercise can help to lower blood sugars by increasing insulin sensitivity and burning glucose. For some people, running can cause hypoglycemia (low blood sugar) during, after, or later in the day or overnight after exercise. But sometimes, certain people with type 1 diabetes can experience the opposite, their blood sugar goes up. This shouldn’t discourage you from running, because once you understand how your body responds to running you’ll be able to manage your blood sugar better.

The type of exercise, duration, frequency, and how trained a person is can also affect your blood sugar. Amanda Kirpitch MA, RDN, CDE, CDN is a nutrition and diabetes expert in New Jersey and weighed in on the topic. She says, “Running can encompass everything from a sprint to a marathon to high-intensity interval training workouts potentially utilizing both aerobic and anaerobic fueling systems. Understanding that these variances are normal and when to expect them can reduce some of the frustration and allow for more targeted insulin and nutrition strategies.”

This variability should be taken into consideration when recommending the type and duration of exercise for a given individual. Additionally, how you manage your blood sugar while running or doing exercise is highly individualized. Your pre-exercise blood sugar level, timing of your last meal, and the amount of insulin you have on board can also affect your blood sugar. Unfortunately, there is no perfect universal science, but once you’ve figured out your own individual trends, you’ll be able to run safely without fearing big glucose excursions (highs and lows). Below you’ll find some general tips for what you need to know.

What Do I Need to Know Before My Run?

You want to know what your blood sugar is, how much insulin you have on board, and what types of foods work best for your pre-run. Kirpitch recommends, “Target glucose pre-exercise is recommended to be around 126-180 milligrams per deciliter (mg/dL). If blood glucose is below target, consuming 10-20 grams of carbohydrates is recommended, more if there is active insulin from a previous meal bolus. If blood glucose is less than 90 mg/dL, then the carbohydrate intake should be higher around 30-40 grams. For runs that are longer than 60 minutes, recommended carbohydrate intakes range from 1-4 grams per kilogram (g/kg) body weight one to four hours before the run. Choosing quick digesting carbohydrates and small amounts of protein and fat closer to the start time may minimize gastrointestinal stress. While, having more substantial meals including fat, protein, and higher fiber carbohydrates three to four hours pre-run is suggested.”

Sometimes blood sugars can be too high pre-exercise. If blood sugars are too high, hyperglycemia can occur because there is not enough insulin to allow muscles to use sugar as fuel. The American Diabetes Association recommends that if your blood glucose is high before starting exercise (250 mg/dL or more), you should check your blood or urine for ketones. If you test positive for ketones, avoid vigorous activity.

Pre-Run Snacks and Meals

If your blood sugar is less than 90 mg/dL, it’s probably best to consume a snack rich in carbohydrate and protein that you do not take insulin for. This will help prevent your blood sugar from dropping during your run.

An example of an easy to digest carbohydrate- and protein-rich snack can be a low-fat Greek yogurt with 3/4 cup of berries, or two slices of toast with a tablespoon of peanut butter.

The amount of carbohydrates you need to consume will depend on your blood sugar pre-run, the duration and intensity of your exercise, and how you respond to exercise. Kirpitch suggests, “Standard recommendation would be about 15 grams of carbohydrate for blood sugar that is less than 126 mg/dL and more carbohydrate for blood sugar that is less than 90 mg/dL.” Pairing this snack with protein will help to delay hypoglycemia. For most people, this snack should not be taken with insulin, while other people may need to take a small amount of insulin.

Insulin Adjustments

Insulin adjustments are dependent on what type of insulin therapy you are on and how you respond to exercise. Some children are very sensitive to exercise and if wearing an insulin pump they need to suspend their basal or long-acting insulin during long bouts of physical activity.

Other people may prevent low blood sugar by eating some more carbohydrate pre-run and keeping their insulin as is. On the other hand, some people need to reduce their basal insulin by a certain percentage during exercise sessions to prevent low blood sugar.

How you adjust your insulin will really depend on your body’s sensitivity to exercise. It’s best to keep a log, track your blood sugar levels, and work with your medical team to create an individualized insulin plan for diabetes.

Kirpitch says, “Reductions in bolus insulin throughout the day as well as overnight basal insulin are important considerations given the increased risk for hypoglycemia that is present for several hours following the activity as well as overnight. Determining how to do this appropriately requires an evaluation of post-run and continued glucose levels throughout the day as well as bedtime blood glucose. Working with your diabetes healthcare team will help to establish appropriate dose adjustments based on the patterns you see with activity as well as frequency of hypoglycemia.”

In a study published in Diabetologia, McAuley and colleagues report on the impact of a 50% reduction of basal insulin delivery before, during, and after moderate-intensity aerobic exercise, but keep in mind this is not necessary for everyone.

Blood Sugar Monitoring

The American Diabetes Standards of Care says, “People with type 1 diabetes should be taught how to use self-monitoring blood glucose and/or continuous glucose monitoring data, food intake, exercise, or pharmacologic therapy to achieve specific goals.” The more frequently you test your sugar the better you will understand how your body responds to exercise.

Frequent blood sugar tests (before, during—about 30-45 minutes in, and after) or investing in a continuous glucose monitor (CGM) can help you to understand how your body responds to exercise so that you can adjust your insulin and carbohydrate intake. Kirpitch says, “Blood glucose should be monitored throughout any activity particularly if someone is trying a new routine or growing their training to more extended runs. If not wearing a continuous glucose monitor, it is good practice to check glucose at 30-minute intervals to assess patterns and adjust management routine.”

While every person with diabetes is different, most people with type 1 diabetes benefit from “maintaining glucose between 100-200 mg/dL during activity,” says Kirpitch. If you are monitoring your blood sugar or wearing a continuous glucose monitor and your bloods sugar drops below 100 mg/dL, “It’s important to introduce some carbohydrate to elevate the blood glucose and avoid having to discontinue the run due to hypoglycemia,” she recommends.

Continuous Glucose Monitor

A continuous glucose monitor (CGM) measures interstitial glucose (which correlates well with plasma glucose). There are two types of CGM devices. Most CGM devices are real-time CGM, which continuously report glucose levels and include alarms for when blood sugar goes above or below target ranges. The other type of device is intermittently scanning CGM (isCGM), which is approved for adult use only. This device does not have alarms and does not communicate continuously. It is said to be less expensive than other CGMs.

A CGM can be helpful during exercise sessions because it helps you to understand how your blood sugar is trending during your exercise session and assist you in making insulin and carbohydrate adjustments.

Carry Glucose Tablets or Another Form of Fast-Acting Carbohydrates

In the event that your blood sugar drops during your run and you experience hypoglycemia, (blood sugar less than 70 mg/dL with symptoms such as dizziness, shaking, sweating, etc.), it is extremely important to be able to treat it right away. Carrying fast-acting carbohydrates in the form of sports drinks, gels, glucose tablets, or jellybeans will bring your blood sugar up quickly and safely. Carry your own fuel can also help to keep your blood sugar stable during a run.

Kirpitch says, “Ideally, with proper fueling, the risk for hypoglycemia can be mitigated, but carrying options for treatment as well as fueling is essential. Fueling can begin 30 minutes into the run and consist of 30-60 grams of carbohydrate per hour for runs lasting one to two hours and 60-90 grams/hour if distances greater than two hours.” This type of fueling during runs is made for very long distance.

If you are going for a shorter run—less than 30 minutes, for example—you are less likely to need to refuel during a run. But carrying fast-acting carbohydrates is always recommended, having it ensures you are prepared in the instance you have low blood sugar.

Can My Blood Sugar Drop After My Run?

Engaging in very long exercise sessions can result in reducing blood sugars, hours or even days after exercising. To combat this, one strategy you may implement is to reduce post-exercise basal or bolus insulin.

Kirpitch says, “Aerobic exercise (like running) most commonly will lower glucose. Reducing basal rates on an insulin pump may be utilized to help mitigate hypoglycemia, however it should be noted that reducing basal rates one to two hours pre-exercise alone has not been consistently effective in reducing hypoglycemia during exercise and can sometimes result in hyperglycemia post activity. The increase in insulin sensitivity can be sustained for 24-48 hours with the highest risk of hypoglycemia overnight following the exercise. Exercising in the afternoon further increases the risk for nocturnal hypoglycemia. Reducing bolus insulin for food around activity and utilizing carbohydrate-containing snacks as needed can help to balance out the amount of circulating insulin and risk for hypoglycemia.”

Timing of Exercise

Insulin levels are typically lower in the early morning hours (pre-breakfast) and glucose-raising hormones can be higher. If you are prone to low blood sugar, running in the morning may be a better option.

“Morning runs may be preferred as they contain the least amount of factors impacting glycemic control given there is no active insulin or nutritional intake after a long period of rest. The decreased insulin sensitivity many people experience in the morning may also put them at lower risk for hypoglycemia but some experience hyperglycemia that is exacerbated by morning activity and find that difficult to manage as well. There doesn’t seem to be a universal optimal time to exercise across populations and often people with diabetes will find a time that works best for them,” says Kirpitch.

She goes on to recommend that, “in an effort to offer the flexibility in timing activity to fit one’s schedule, it is best to check often and learn the patterns and best techniques for the period of time you can fit in activity. People who only limit their window of opportunity for exercise to what might be the best from the perspective of glycemic control, often find it to be limiting and unreasonable.”

Automated Insulin Delivery Systems

Emerging evidence suggests that automated insulin delivery systems may lower the risk of exercise related hypoglycemia. This type of system consists or three components, an insulin pump, a continuous glucose sensor, and an algorithm that determines insulin delivery. Such a system can be advantageous because insulin delivery can not only be suspended, but also increased or decreased based on sensor glucose values.

Can My Blood Sugar Rise During a Run?

Typically, hyperglycemia occurs during short bouts (less than 30 minutes) of high-intensity workouts such as interval training. These types of exercises can cause the body to release hormones such as adrenaline, which is released as part of a stress response and raises blood sugar by increasing the production of glucose by the liver.

Sometimes, it is recommended to do these types of exercise before running so that blood sugar levels are less likely to drop. But it’s also not entirely out of the ordinary for blood sugar to rise, particularly during longer runs when runners are ingesting carbohydrates to fuel their run.

To combat potentially high blood sugars, some experienced long-distance runners, “Find it helpful to utilize increased basal rates or a small bolus of insulin to counteract the rising glucose levels that can occur during a run,” says Kirpitch. This is highly individualized and is typically utilized when a person with diabetes has more experience with blood sugar management and longer runs.

High blood sugar can affect exercise performance and can be dangerous if levels are too high. Kirpitch says, “Runners and other athletes often note a decrease in performance and increase in fatigue as glucose rises above 200 mg/dL, however it is not usually recommended to utilize corrective insulin until the blood glucose is running 250-270 mg/dL and higher. If blood glucose rises to greater than 270 mg/dL and ketones are present, activity should be ceased to prevent ketoacidosis. At this point, a corrective insulin dose should be administered, and adequate hydration should be encouraged.”

But, whether or not you bolus for high blood sugar or increase your basal rate during your run will really depend on your level of experience and comfort in managing your blood sugars.

Other Reasons for High Blood Sugar During or After Exercise

Fear of hypoglycemia is normal. Experiencing a low blood sugar can be scary and the need to prevent it overwhelming. Sometimes people with diabetes aim to prevent low blood sugar during or after exercise by overcompensating with excessive amounts of carbohydrates or reducing insulin too much. These strategies can result in high glucose levels during or after exercise.

To prevent this from happening, it’s important to get support. Work through your fear with endocrinologist or medical team and come up with a devised plan to prevent hypoglycemia. The more education you have the better equipped you’ll be. It’s easier said than done, but you can do it. Remember that type 1 diabetes doesn’t discriminate. In fact, some professional athletes have type 1 diabetes, so if they can do it, you can too.


For some people with type 1 diabetes, certain types of exercise are contraindicated. If you have retinopathy, peripheral neuropathy, autonomic neuropathy, or diabetic kidney disease, you should discuss exercise with your healthcare provider before beginning a running program.

A Word From Get Meds Info

If you have type 1 diabetes, exercise is important. If running is your exercise of choice, you can learn how to maximize performance and prevent low and high blood sugar by adopting some strategies. While there is no universal recommendation, as everyone with diabetes is so different, figuring out your patterns will be the key to success. Some other things to consider include supplementing with carbohydrates prior to exercise with or without bolus insulin, reducing pre-exercise long-acting insulin (a task that is easier for those people on insulin pumps), reducing pre-meal bolus if exercise occurs with two to three hours of a meal, reducing post-exercise basal/bolus insulin to reduce the risk of night time or delayed post-exercise hypoglycemia, and using a continuous glucose monitor to provide frequent blood sugar readings and guide insulin reduction and ingestion of additional carbohydrates.

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