If your blood sugar is too high and you don't have enough insulin in your system, you are at risk for diabetic ketoacidosis (DKA); this is no different during exercise. In fact, you will be putting more of a demand on energy requirements, which may exacerbate this condition.

If your blood sugar is high, but there is not enough insulin to allow it to be taken out of the bloodstream, your body won't be able to use it for energy and fat will be broken down to fuel your exercise. Ketones are a byproduct of the body using fat for fuel. Although ketones are a natural byproduct of fat consumption, too many ketones can cause a chemical imbalance that overwhelms the body: diabetic ketoacidosis (DKA). You can test for ketones using a simple urine test, which can be purchased from your local drugstore (i.e. CVS, Walgreens, RiteAid, etc.) for anywhere from $6-$15 for 50 tests. DKA is a life-threatening condition; do not start exercise if your blood sugar levels are 250 or higher and you test positive for ketones or if your blood sugar levels are 300 or higher even without the presence of ketones.¹ Take a rapid-acting insulin to lower your blood sugar levels.

If your blood sugar is high but you have insulin in your system and you're merely high because you miscalculated an insulin dosage, then extended aerobic exercise will most likely lower your blood sugars. Therefore, in this case, you should be able to safely exercise; many find that exercising alone will reduce their blood sugars. You can also consider taking a small dose of rapid-acting insulin (0.5 -2 units), waiting 10-15 minutes and then beginning your exercise. The main danger here is overestimating your insulin needs, which could result in a low later.¹

However, do not, under any circumstances, begin exercise when you have ketones in your system. If you have ketones from an infection, being ill, or from having high blood sugars for an extended period of time, do not exercise until you get your blood sugar under control.¹

If my blood sugar is within a normal range, which for a diabetic the target is between approximately 80-120, and I do not have high levels of insulin circulating in my system, I will likely start my workout without consuming any additional carbohydrate. If I will be exercising for a prolonged period of time (more than an hour), I will likely need to consume carbohydrate during the workout. Remember, no matter how short or long the exercise, ALWAYS have a supply of fast-acting glucose source with you.

If my blood sugar is within a normal range, but I have moderate to high levels of insulin circulating in my system, I will most likely consume some carbohydrate to cover it….typically a food with a low glycemic index, but with a lot of carbs (a medium glycemic load food). I will take into consideration how much 10 grams of carbohydrates will bump my blood glucose up. For me it’s 40 points (you can help establish this number for yourself in our Management Tools area). This may or may not be an adequate amount to satisfy the entire workout. I don’t want my blood sugar to get too high so if it is a prolonged workout, I’ll be sure to have extra carbohydrates available and test to see how the duration and intensity is affecting it. During the workout, I will eat something with a high glycemic index for quick energy and blood glucose recovery. Always, always, always have some sort of glucose source available during your workout.

If my blood sugar is 100 or less, I will consider eating some carbs before I head out the door. If it is significantly low, I will not leave until I have eaten carbs and pulled my blood sugar back in to a safe range. However, if you're closer to the 100 end of the spectrum and are on a temporary basal rate on your pump or have low levels of circulating insulin for other reasons, you may not need to eat anything. But watch this carefully. Testing and experience will help you determine what works best for you.

Most diabetic athletes eat something before longer workouts, but may not need to eat anything before weight training, sprints, or other harder, shorter workouts. ¹

How They Work: The first thing to know is that carbohydrates are, hands down, the most important fuel source for any type of exercise. Carbohydrate is stored primarily in the muscle in the form of muscle glycogen, which is the body's number one source of fuel during moderate and intense aerobic exercise. When your body needs fuel, it will break down this muscle glycogen to be released into the bloodstream as glucose. Your muscles will primarily rely on muscle glycogen for fuel during exercise, as long as it's available. The longer and harder you exercise, the more these muscle glycogen stores become depleted; your liver can also store glycogen (although a much more limited amount) and release a minimal amount of glucose into your bloodstream during exercise. However, once you've depleted both of these stores of energy, you're going to get fatigued and you’re going to get low!

This is why even non-diabetic athletes need to replenish their carbohydrate supplies during prolonged exercise. When you ingest carbohydrate, it is broken down and released as glucose in your blood, thereby continuing to fuel your activity. Carbohydrates are rapidly metabolized and can begin to show up as glucose in your bloodstream within 5 minutes.

Though insulin is necessary to utilize these carbohydrates as glucose, it is extremely important to understand that your insulin efficiency is enhanced with exercise and you may not need any additional insulin as you’re consuming these extra carbohydrates during exercise. And we will continue to repeat this…always, always, always have some type of fast-acting carbohydrate on hand.

Glucose Monitoring: The type and amount of carbohydrate you consume should depend on how long you plan to exercise, how intensely you plan to exercise, and your blood sugar and insulin levels before and during the workout. Glucose monitoring is essential for insulin-dependent diabetics, so it is important to test your blood sugar during the workout, especially if it lasts longer than an hour. Figuring out what works for you in terms of carbohydrate consumption will take a lot of trial and error and monitoring your glucose levels will help you establish patterns and make necessary changes in your routine. Your body's reaction will also vary among different types of exercises, so even if you have a pretty solid grasp on how to handle let's say, a 5 mile run, for example, if you start a new routine that involves boxing, you will need to do more testing and trial and error. The moral of the story is: Test, Test, Test!

Use Carbs to Treat Hypoglycemia: If you are suffering from hypoglycemia (you’re getting low) during exercise, consuming a carbohydrate with a high GI (see Daily Management) will raise your blood sugar the fastest. Go for glucose tablets or gels, sports gels like Gu or Hammer Gel, Clif Shot Bloks, regular soda, candy, sports drinks such as Gatorade or Powerade, cookies, etc. An advantage to taking glucose tablets, gels, or liquids is that they are already in their simplest form and your body does not have to go through any additional "work" to convert them to the form it needs - glucose. Other simple sugars like the fructose found in fruit, have to go through an additional measure to be converted to glucose, and therefore don't act quite as rapidly. Another advantage to glucose tablets, gels, and liquids is that they come in precisely measured amounts, allowing you to more easily predict their effect. However, when you need to boost your blood sugar you need to do it immediately, and you might not always have the perfect solution on board. Use any carbohydrate you can find, preferably one with a high GI.

An interesting fact to note is that foods with higher fat content have a slower rate of digestion and absorption than foods with a lower fat content. Therefore, eating a doughnut would not boost your blood sugar as quickly as drinking a regular soda, for example. However, a doughnut is technically considered a high glycemic index food; this is just an illustration to show that the doughnut will not boost your blood sugar as quickly as the soda. It’s still going to boost it quickly.

High GI Foods: glucose tablets, gels, or liquids, sports gels like Gu, regular soda, candy, sports drinks, cookies, sugary cereals

Medium GI Foods: orange juice, bananas, grapes, oatmeal, rice, pasta, yams, corn, baked beans

Low GI Foods: high-fiber sources like apples, cherries, dried beans and legumes, dates, figs, peaches, plums, whole milk, yogurt

Sometimes you might just need that quick boost; however, if you're low and likely to continue dropping, you may need to take in something with some additional staying power that includes some fat and/or protein to go along with your carbohydrate. PowerBars, Clif Bars or peanut butter and crackers, for example, contain fat and protein in addition to carbohydrate; this can help prevent your blood sugar from falling as much later during long workouts.

If your exercise will last an hour or less, and you start with normal blood sugar and moderately low insulin levels, you should not need to take in any additional carbohydrate, as long as your muscle and liver glycogen stores are not depleted (i.e. you recently performed a long-lasting and/or high intensity activity such as a marathon). However, if you are running on depleted glycogen stores or your insulin levels are high, you will probably need to supplement with carbohydrates even for activities lasting an hour or less.

For prolonged activities (lasting an hour or more), you will likely need to take in some additional carbohydrate both before and during the exercise.

Replenishing glycogen stores after exercise: When you finish any exercise, particularly long and/or intense ones, your glycogen stores will be depleted and they won't replenish themselves. You need to do it! Your body replenishes its glycogen stores most rapidly during the first 30-120 minutes after exercise, so it is critical that you consume carbohydrate during this time. This will do two things for you:

1) Reduce your risk for lows following your workout.
2) Ensure that your glycogen stores are replenished for your next workout, thereby reducing your risk for low blood sugar during your next workout.

In general, you want to have glycogen stores available.

Remember that you are at risk for post-exercise lows for up to 24-48 hours after your exercise, depending on your workout’s length and intensity. Consuming an appropriate amount of carbohydrate after your workout will reduce this risk and you will most likely need minimal insulin during this period. During this time, you need to understand how your insulin efficiency (carbs to insulin ratio) can drastically change. See the Daily Management section.

**Tip: If you are trying to lose (or maintain) weight and don't want to consume the extra calories necessary to prevent lows, minimize insulin levels to the best of your ability during all activities.

How It Works: Fat is metabolized much more slowly than carbohydrate and is not available to your body as a fuel source until approximately 5-6 hours after you consume it. It can be found stored in your muscles and circulating in your blood and can be used to provide energy for some low intensity, longer duration exercises, but is hardly used at all in high intensity anaerobic or aerobic exercise. When you are resting after exercise, however, fat is largely used to fuel the energy for your recovery. ¹

Use Fat to Prevent Hypoglycemia: Fat can be used to prevent later onset lows after exercise. Eating a high fat bedtime snack like soy milk, yogurt, or ice cream can help stabilize your blood sugar overnight on days you've been particularly active. ¹

Recommended Intake: Typical recommendations for fat intake are 20-35% of your total daily calories. Diabetic exercisers can consume slightly more than this in an effort to prevent late onset lows. If you do this, however, opt for "better" fats (those that do not increase LDL cholesterols and increase your risk for heart attack or stroke) such as olive oil, nuts, peanut butter, fish, flaxseed, or dark chocolate or lower fat version of dairy or other foods (i.e. ice cream, yogurt, cheese). Avoid saturated fats (solid at room temperature; i.e. cheese, meat, margarine), trans fatty acids, and interesterified fats (a new substitute used for trans fats). These can all raise LDL cholesterol levels and increase your risk for heart attack and stroke.²

How It Works: Protein is never a primary energy source, but it is crucial in muscle repair, recovery, and growth (more on that below). It takes about 3-4 hours for the body to metabolize protein, so it is metabolized more quickly than fat, but slower than carbohydrate.¹

Use Protein to Prevent Hypoglycemia: Because protein is not a primary energy source, it is not necessary to consume it before or during exercise. However, supplementing your carbohydrate intake with protein (in a ratio of 4:1) after exercise can help keep your blood sugar more stable and prevent late onset lows. Like fat, protein may also be beneficial as part of your bedtime snack to reduce the risk of nighttime lows after a day of extended activity.¹

Most importantly, running low on carbohydrate stores will induce the dangerous state of hypoglycemia, but it will also affect your ability to exercise and perform your activity to the best of your ability. As carbohydrates are the main source of fuel for all types of exercise, running low on carbs means sluggishness, tiredness, extreme fatigue, and may lead to that feeling commonly referred to as "hitting the wall." Appropriate carbohydrate intake benefits the performance of all athletes, diabetic or not.

Because carbohydrate supplies are so intimately linked to both getting low and to performance, most of the recommendations for carb intake are listed in the above section "Preventing Lows." However, techniques such as carbohydrate-loading can also be beneficial to diabetics' performance and are discussed here.

Carbohydrate Loading for Diabetics: Carbohydrate loading, also known as carbo-loading, before a lengthy event (anything lasting longer than one hour) can benefit all athletes if done correctly because it allows you to begin the event with fully compensated, sometimes super-compensated glycogen stores. Remember, glycogen is your body's main source of fuel during exercise, so having full glycogen supplies for a long event is like having a full tank of gas for a long drive - you're going to make it a lot further before you run out.

Traditionally, carbo-loading has consisted of 3-7 days of increased carbohydrate uptake, or 3.6-4.5 grams of carbohydrate per pound body weight. This is coupled with tapering the frequency, intensity, and duration of exercise during this time period, so that you don't burn through the glycogen supplies you are storing up.¹

As a diabetic, for your carbo-loading to be effective, you must have sufficient insulin in your system to allow your muscles to take up the glucose. Sufficient insulin levels are necessary to prevent hyperglycemia (high blood sugars) and to allow maximum glucose uptake and ensure proper glycogen storage in the muscle.¹

Also, go for carbohydrates that are higher in fiber and with low GI to prevent excessive increases in blood sugar levels and still achieve the effect of carbo-loading.¹

Managing all of this can be tricky - if you can't keep your blood sugar under control during carbo-loading, stop and try again next time. Out of control blood sugars are counterproductive and their risks will outweigh the potential benefits of carbo-loading.

Fat is not nearly as useful to your body during exercise as carbohydrates. A technique called fat-loading (eating high fat foods prior to your activity) can be harmful to your performance. Use fat in moderation as a tool to control your blood sugar levels, but not as a primary source of energy for exercise.¹

Protein, though not a key energy source, is important to exercisers for other reasons. It allows your body to repair the muscles after exercise and promotes the synthesis of important hormones, enzymes, and other tissues. Consuming an adequate amount of protein is essential if you wish to see any improvement in muscle endurance, strength, or size.

If you exercise regularly, you should consume at least 0.5 – 0.8 grams of protein per pound of your body weight.¹ To calculate this, simply take your body weight (in pounds) and multiply it by 0.5. Then multiply your body weight (in pounds) by 0.8. Write these two numbers down. Your daily consumption of protein (if you exercise regularly) should be between those two numbers (in grams). So, for example, if you weigh 180 pounds and you exercise regularly, your daily protein intake should be between 90 and 144 grams of protein. Here are the general protein contents of some common foods:

• 8 oz. piece of meat: 50+ grams of protein
• 8 oz. container of yogurt: 11 grams of protein
• 1 oz. cheese: 7 grams of protein
• 1 cup of milk: 8 grams of protein
• 1 cup of dry beans: 16 grams of protein

Eating protein before or after your activity will not boost your performance; however, eat protein after exercise to aid in muscle recovery, help build muscle, and to help your body more effectively replenish its supplies of muscle and liver glycogen.