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High blood sugar after exercise?

June 26, 2015 by Scott Johnson

From Markus Berndt: It’s one of the first recommendations you get after being diagnosed with diabetes. “Get active, do more exercise, it’s good for you!” And since we’ve been a child we’ve heard that exercise is healthy. If we do it consistently we’re rewarded, literally, with an awesome beach body.

Adding exercise into our day is also good for our diabetes. We’re taught that exercise lowers blood sugar, right? But can the opposite also be true? Can you have high blood sugar after exercise?

Up close

We now know that physical activity usually lowers blood sugar because it reduces how much insulin is needed to move sugar into the cells.

While, in the past, most experts advised frequent training intervals at moderate intensity, but recent studies have shown that even short, intense workouts are very effective. For example, a 15-minute intense weight training lowered blood sugar even more than what’s seen in some endurance training.

So activity lowers blood sugar – but not always!

Personally, I experienced this very early on and was extremely irritated! I just learned that exercise lowers blood sugar, but an intense 45-minute run consistently resulted in higher blood sugars than when I started! What in the world?

At first, I was confused and felt like I didn’t understand the world anymore. Then it was more of a “would you look at this?” kind of thing. And finally, I was determined to figure out what was happening. I knew there had to be an explanation.

Why does exercise sometimes raise blood sugar?

Exercise can trigger the body to release stress hormones, like adrenaline which stimulates the liver to release glucose or cortisol which makes you more resistant to insulin. And strenuous activity, especially competitive sports, triggers increased stress hormones, in which case blood glucose usually increases (at least temporarily).

In general, we know that different exercises affect us differently. And we also know that we’re all very unique, and the same exercise affects different people differently. Our blood sugar response will also depend on our level of physical fitness and personal exertion. Generally speaking, 30-40 minutes of running brings different results than an hour of cycling, swimming or even boxing. The intensity of the activity is often as important as the duration.

Finally, even though it can be unsettling, we must be persistent! A high blood sugar is annoying, especially after exercise. Nevertheless, exercise and activity are very good weapons against your diabetes monster and they work in your favor in the medium to long term, even if you’re struggling against those BG boosting stress hormones in the short term.

Generally, the post-exercise blood sugar spike settles down and returns to normal after an hour or two, so check again after some time if you’re able to. And the exercise itself pays dividends for much longer than that, so the tradeoff is well worth it. However, if you notice that things aren’t moving in a good direction I recommend making an appointment with your diabetes care team to talk about it. There are many options available, and they’ll help find something that works well for you.

Good info, Markus! Thanks!


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  • amy

    that article was not very helpful. I am type 1 and try to be in ketosis most of the day. I do high intensity interval training everyday for about 40-60 minutes. I found that if I exercise in a fasting state my blood sugar goes up afterwards. However if I eat 5-6 hours before exercising then my blood sugars are fine. I believe this has to do with restoring glycogen to the muscles. Fat takes longer to breakdown into energy than sugar. so when I eat before I have readily available glucose in my muscles, and the liver does not need to respond by raising blood sugars until my body can supply the rest of the energy needed through fat/ketosis. This is just my theory … but I have done a lot or research on it. If I DO end up working out without eating first (i usually try to have a few blueberries or something 2-3 hours before in worst case) … then I take a couple units of fast acting insulin (humalog will take about 10 minutes to work) right before the work out. This has proven, for me at least, to reduce my afterwork out highs by about half.

  • Thanks for the feedback, Amy, and for sharing so much of your experience. Very interesting!

  • Bobby McDaniel Jr.

    Amy, just to be clear; in order to maintain good blood sugar during exercise I should eat several hours before ? I have high blood sugars when working out. Also, what should this meal consist of ? Carbs/fats/etc

  • Tuki

    Dear Readers,

    I find this article interesting and true, to keep my blood sugar spike in the morning at a minimum I go to the gym right after I wake up. This helps stabilize my sugar lever and keep it under 100 mg/dl. You have to understand your body needs more sugar when you work out (I am eating also a high fat low carb diet) and if you do not have enough sugar in your blood and still have some stored the body will release it and you will have more then your insulin level can handle then you will have a higher blood sugar when your workout ends. What I can recommend if you are not in ketosis, that you eat something before you go to the gym so your body wont release any glycogen stored, if you are living the keto lifestyle then your body should be fine with the ketones that you have and it should not produce any excess sugar. Take in consideration that every Type 1 is different. For ex. I still have days where I do not use any insuline and I still keep my blood sugars in the 80-90mg/dl range, but there are days where I need both types of insulin to keep my levels in control. Anyhow exercise is a must and a good investment in the long run even if it rises your blood sugar levels.

  • Araoli Murugayyan

    Dear Readers,

    My sugar level goes up after jogging. (45 min jogging)

    What should I do?

    Can I neglect that sugar reading after exercise?
    Can I stop jogging or reduced duration?
    Shall I eat something (carbo / sweet) before jogging?

    Please suggest friends.


    I’ve adopted an “intermittent fasting” protocol to address my T2D and my weight. So far, I’ve lost 45 lbs., and my fasting BG is about 105. But after I exercise, in my case, playing 2 hours of intense racquetball and some weight lifting, my BG spikes to 240+. After about an hour post-exercise, my numbers plummet to 90-ish. From what I’ve learned, since my last meal was, nearly, 24-hours ago, the glucagon has been converting body fat to glucose to feed my muscles, and during the hour AFTER exercise, that sugar gets converted to energy and for muscle regeneration.

    Finally, most doctors get their patients to “chase the numbers.” I believe it is much more important to understand WHY we have higher glucose numbers than to take something to make those numbers go down. Transient spikes in BG should not be that much cause for concern if the overall trend is getting the A1c to a normal range.

  • Excellent point!


    Thanks for your reply, Scott. I was diagnosed a T2D in 2003, when my A1c rose to 6.8, I was just 40 years old then. Since that point, I’ve been learning about how and why I got to where I am, and for my condition, the simple truth is I became insensitive to my body’s production of insulin. Thus, the only protocol for me was to reset my body’s insulin sensitivity, which I did through fasting.

    How did I arrive at this protocol?

    I kept reading stories of obese individuals who received bariatric surgeries, the actual type was irrelevant it seems, who after a few days, no longer needed their T2D medication–it appeared that they were cured. Time and time again, stories were told about how Mr. or Ms. X no longer needed any medication after their bariatric surgery.

    So then, the question for me was: Can I get that same result WITHOUT the surgery?

    The answer is yes, but it isn’t as easy you’d think. It takes a bit of time and a lot of willpower. For most, I’d say a couple of weeks of eating high-fat, low-carb, and no more than 400 calories per day for a total “reset.” Then after that, eating a modified Paleo/Atkins will continue to maintain your hard-earned gains. So far, I’ve kept my weight off for 2-years, and I still don’t need Metformin, or any other blood-sugar reducing medication.

    Finally, I keep reading about those who panic over the liver-dump of glucose during strenuous exercise as something to battle. Once educated, those whose blood sugar rise to levels that most medical practitioners would consider “unhealthy” should understand that the high blood sugar level indicates that our body is getting rid of the excess sugar that created our condition in the first place–too much sugar in our diet that ended up on our gut or backside.

    Therefore, trying to stop this from happening is like putting a “STOP” sign to weight loss, when in its place, we should be ensuring that we are hydrated enough with a bit of salt and potassium to replace what our body is getting rid of: Excess sugar.

    Be well

  • Fascinating stuff, I really appreciate you sharing! That reset sounds so important. I’ve read a lot of stuff over the past couple of years about our bodies fighting so hard to stay at that higher caloric level that they get accustomed to (stupid caveman genes! 🙂 )

  • Thermal deal

    you cannot cure yourself from Diabetes like you can with gastric bypass surgery. The reason you do not have to take metformin at this time is because you have your diabetic symptoms under control through diet and exercise. You still have diabetes and will relapse into dangerous symptoms if you come of your diet and exercise routine.

    When a patient gets gastric bypass surgery they are actually curing their diabetes disease. This is because after gastric bypass the small intestine starts producing Glut-1. Glut-1 is a molecule that helps control glucose in the body.

    But great job controlling your diabetes. You should have a long and healthy life the way you are taking on your disease.

  • Thermal deal

    start off by jogging less. Read your blood sugar levels at different intervals and slowly build up until your body adjusts your to your exercise levels.

    lower impact or less duration until your body adjust is always recommended. You do not want to spike your sugar up to levels where you are causing harm to your body.

  • Thermal deal

    depends if you are type 1 or type 2 . Both disease have similar names but are completely different diseases.


    Thank you! But wouldn’t the same physiology occur with serious fasting similar to the effect of “gastric bypass” that would result in diabetes reversal? Why would bypass surgery “cure” diabetes, but serious fasting not? All I know is it works for me, and has for the past year and a half.

    Thanks again,


  • Kathy Braun

    I too am experiencing high sugars after an intense work out on the elliptical. Should I eat before or not is the question. Thanks to all who can help.

  • Alex Soury

    You are controlling your T2D with diet and exercise. In order to cure it you need to regain your insulin sensitivity and your Paleo/Atkins diet is no helping, in fact its the cause.

    Fat, especially animal fat and saturated fat impair insulin from doing it’s job thus requiring more and more. Saturated fat can also kill the insulin producing beta cell of the pancreas.

    Switching to a low-fat whole-food plant based diet will restore your insulin sensitivity.


    Alex, the medical community disagrees with you. I know you believe what you say, in other words, you are genuine in what you believe, if you were to seek information outside your realm of sources, you might see something different.

    For example: Yale Medical School tried to debunk Atkins, and it failed miserably. In fact, JAMA and its British equivalent, both recognize that no insulin is needed to break down fat, so no insulin is produced, which is where T2D comes from–it is called “insulin resistant” diabetes is it not?

    Finally, no credible medical study exists for your “fat impairs insulin from doing its job” claim. If this is what you’ve been taught, I implore you to reconsider the source. Atkins, Fung, and Yale Medical School have found that a high fat diet, low in carbs, especially from simple sugars like potato, carrot, corn, rice, and wheat, and all grains for that matter turn into, promotes less internal inflammation, a reduction to blood sugar, and an increase in better health. This is not my opinion, this comes from those who know, and have studied this fact.

    As always, be well.

  • Joel

    I’m T2 for 5 years now, just diet and exercise to control. usually stay around a 5.5 A1C. I do notice that sometimes when I exercise hard ( mountain bike Spring, Summer, Fall, and Ski Winters ), Sometimes I notice my B.S. goes a little higher than I would expect after heavy exercise. I find it’s more related to what my weight has been doing. I’m 6 feet, when my weight is above 185, I notice the increase, when more around 175. I have to watch for moderate decreases ( mid 60s ). I kind of wrote it off to have a store of easy to use fat to convert to sugar. My diet is Pescetarian and has worked well for me. My Nemesis is the occasional Ice Cream binge.

    When I started this, I was 200lbs, before meal B.S. was 350, found out by accident. By the time I saw a doc ( wanted to research all I could first ), had B.S down to 200. A1C when Doc checked it was just under 10%, have now idea what it must have been when my B.S. was 350.

    The plus for me on all this is it motivates me to stay in better shape.


  • Gopi ranganatha

    My parents have type 2 dibatic. I had hba1c was 6.8% on last year December and on April this year 5.3% for hba1c. But the PBS always between 110 – 130mg and PBS is130mg in morning after breakfast, lunch is between 115-130mg and dinner 156mg. Am I really dibatic?????

    And I am taking medicine tenglyn 500 m (metaformine 500mg and teneligiptin 20mg)

    Today I checked my FBS is 115mg and I exercised morning after 5mins I checked blood sugar is high like 134mg. Is there any risk of future diabates?

    Should I stop this medicine or continues? Let me help.

  • High fat? Do you know that Dr. Adkins had severly clogged arteries when he was autopsied? Fat is the cause of diabetes. Switch to 80 percent cqrbs and 10 % each fat and protein. Doctor Dean Ornish has been reversing diabetes for the past thirty years by having his patients follow this. As a vegan I can attest that my diabetes was reversed after 14 years but stopping the consumption of animal products and processed foods. Eat whole natural foods: fruits and veggies, beans, nuts, avocados and grains.

  • I cannot believe anyone is recommending a high fat diet for a diabetic! Google whole foods plant lifestyle. You will find so many doctors recommending a LOW fat diet to reverse diabetes. Watch the documentary Forks over Knives and you will never eat another animal product. Here are some basic differences between animals and plants.
    Animal products contain NO fiber. You should have at least 40 grams a day. Only plants have fiber. Animals on contain macro-nutirents) fat, carbs, protein) but plants contain micro-nutrients as well. They contain everything to restore one to good health. The USDA is supporting factory farms. This is where they load the animals with drugs to get them fat and keep them from getting sick from standing in their own feces and urine for their entire lives. The lates documentary is What the Health. Google plant based lifestyle and you will find Drs. Neal Barnard, Mike Greger, Dean Ornish, John McDougall, joel Fuhrman, Caldwell Essylsten, T.Colin Campbell, Garth Davis, Mike Klaper, and so many others. All recommend High Carbs, Low Fat. I can attest that as of March 1, 2017 I switched from eating animals and processed foods to a plant based diet. I was 235 poundS BMI 36, had diabetes for 14 years, high blood pressure. On April 30 – 61 days later, I was no longer taking any medication, my weight was down to 202, my blood levels were normal as was my blood pressure. Eat high fat as you wish but you will only worsen your diabetes and be taking medication for the rest of your life. Doctors are not taught anything about nutrition during their schooling. They apparently forgot what the first doctor taught 2000 years ago: Let food be they medicine – Hippocrates. Finally, google American Diabetic Associateion/support and you will see who is funding them: the meat industry, the dairy industry. etc It is no wonder they do not recommend stop eating animal products.

  • Jeff Kershner

    I am not a doctor, but I recommend you try intermittent fasting and monitor how that affects your blood sugar. I am not diabetic, but I had a fatty liver and higher than normal A1c which meant I was going down the path to type 2. After doing intermittent fasting, and generally reducing crappy carbs and increasing my fats, my a1c is now 4.9 and my fatty liver is gone.

    As for your medication, I can’t answer. I prefer not to take any medication if possible but you have to do what you have to do.

  • Jeff Kershner

    Again.. I am no doctor, but if your A1C is consistently around 5.5, I would say your diabetes is gone. I know they say there is no cure for diabetes, but since a A1C is a 3 month average of blood sugar and 5.5 is a great number, I think you are good!

    This doesn’t mean you can eat pizza, cake and cookies like we did when we were younger, but just monitor and track your levels and you should be good.

  • Joel

    A1C is not the whole picture. If I am not careful, I can still get high spikes and all the damage that goes along with it. My doctor has told me that even though I have good control, I am still at risk for everything that goes along with type 2. So, no, it’s not gone. As you say, I still have to watch what I eat, though I sneak in some things I shouldn’t on occasion.


  • Jeff Kershner

    Yes exactly.. that is why they say you can’t cure diabetes, but with good control, you can manage it as if it is no longer an issue for you. Its like alcoholism. Someone can stop drinking and essentially they are not an alcoholic anymore…. This doesn’t mean they can drink again.

  • Kate Wren

    Thanks so much for this information. I just started exercising and after my workout my blood sugar really spiked. I was worried. Great information.

  • Dale

    Very good amplify!!! If we continue to hammer our body with bad stuff eventual you wear down the body’s ability to function. Yes Type 2 diabetes can be reversed and you body (which is constantly working to return to a state of “homeostasis”) will heal itself and begin functioning properly. Yes we can’t return to behavior that put us in this situation in the first place but we can live a normal life making good choices! What an novel idea! Just the way God intended…..normally making good choices results in good benefits. Encourage and keep hope alive!!!

  • Clint Harris

    Just eat fish and poultry. No steaks or red meat and you will just fine with the Atkins diet. Study has found a decrease in cholesterol after an Akins diet. When you die at 80, I’m sure they will find clogged arteries as well. Even on a Vegan diet.

  • Clint Harris

    Ok. You guys are getting ridiculous. I know many vegetarians that are type 2 diabetics. You can’t just eat veggies. Your body needs sufficient amount of proteins and you can not get that from just veggies.

  • Clint Harris

    That has got to be a good thing. Eventually, the body will lose it’s fat reserves and your liver will produce less Glucagon. The spike is temporary. It is the long term high BG that does the damage.


    I’m not a doctor, and I don’t even play one on television, but I was under the impression that the liver motivates the pancreas to produce glucagon. But your overall representation of what happens is spot on.

    The only other thing I’ve learned lately is that “glucotoxicity” is not as “toxic” as doctors think it is. I invite you to do a bit of research about why doctors think that high blood sugar is bad, and you’ll find out that when it comes to actually causing mortality, high blood sugar is not as responsible as we might have thought.

    Now, don’t get me wrong, I believe that there is a point that it starts causing problems like neuropathy, blindness, and other stressors on the body, but a constant 130-150 BG is not as bad as it was once thought to be. Again, check my facts out, but I believe that I’m right.

  • CW

    Of course you can get sufficient protein from a ‘plant strong’ diet.

  • Here’sJohn J

    Here is why the high-fat diet works, but first a couple of important points:

    1. The muscles and liver contain glycogen, a form of sugar for immediate use.
    2. When blood sugar gets low, the liver converts ITS OWN glycogen into glucose and releases it into the bloodstream; the glycogen in the individual skeletal muscles cannot share it with the rest of the body like the glycogen in the liver.

    When the liver and the muscles run out of glycogen, there are 3 ways the body creates blood sugar, or, glucose: 1- digestion of carbohydrates; 2- conversion of body fat; and 3- conversion of amino acids (protein, or, skeletal muscle).

    During periods of fasting, skeletal muscle tissue and body fat are used in roughly the same proportions. When carbs are eaten, the body ceases to produce glucagon, thus ceasing to convert fat/protein into glucose.

    The idea behind high intensity training is to use up the glycogen in the muscles and the liver, and force the body to produce blood sugar from the body’s fat stores. The newly converted blood sugar in jammed into the sugar-depleted muscles, and as long as you refrain from eating carbs the body will continue to convert fat/muscle into glucose.

    Eating carbs after exercise defeats this process because you replenish blood sugar from what you eat instead of what you already have stored around your ribs and other places. Instead, try eating a boiled egg and a couple of sausage links or pieces of bacon and drinking a quart of water immediately after exercise.

    Carb usage should be no more than 5% of daily caloric intake, with protein about 35% and fat about 60%

    It will take the body a couple of weeks to adjust to this diet, during which time mitochondria in the muscle cells will multiply like crazy in order to adapt to using fatty acids as a primary energy source, rather than sugar.

  • Here’sJohn J

    If you’re not Type-1 or hypoglycemic, you should be able to work out without eating prior.

    Your liver converts its stored glycogen into glucose and releases it to the rest of your body so it can be used by your hard-working muscles. Your glucose number should go down over time because your blood sugar is being transported into your muscles. If you eat carbs after a workout, your liver will stop converting glycogen into glucose because it won’t have to.

    You will know when you have completely depleted your muscles of glycogen (which is good, but really hard to do) because they will get all jelloey and shakey, and you might feel like you have to barf. But it could take a couple of hours of aerobic/anaerobic interval training to do that, much longer if you stay in the aerobic zone.

  • Disappointed

    I’ve been swimming 45 minutes per day since about 2 weeks – a rather intensive workout with hand paddles and restricted use of my legs. Today, I took a bit of raisin sugar (about 12 grams) and I went from around 144 to over 400 about an hour after the swim. I’m trying to be consistent during my workout so I can adjust accordingly but the random reaction is difficult to deal with. I usually try to start with a higher end BG so the lifeguards don’t have to call 911 and fish me out of the water.

  • Yeah, that’s a bummer! I’m sorry you had to deal with that. I play basketball regularly, and I feel that I have a good system in place to keep me where I want to be (combination of timing, a temporary basal rate on my insulin pump, and some carbohydrates between games), but even with tons of practice and repetition, there are days where things go their own way. It’s frustrating for sure. But what’s that old saying? Fall down 7 times, get up 8? Feels more like 70 times, but maybe I’m stubborn. Keep at it, and keep trying. I have no doubt you can figure it out!

  • Dan

    I went from a 13.5 a1c to a 6.3 a1c in under 3 months on a high fat diet and no longer require insulin. My blood sugars become more stable by the day. I spent hours and hours researching the vegan doctors you mentioned when I first got sick, and respectfully, none of those doctors would recomend eating animal products regardless of any nutritional science because they believe it is morally wrong. I eat a lot of plants, I think eating nutrient dense food is very important. I eat hight fat, moderare protein, low carb(low G.I. in particular), high fiber and all the nutrient dense whole foods i can. If the option is mcdonalds vs whole nutrient dense foods then of course the second option is better. But what you said about high fat and diabetes is just not true.

  • Paul

    I look at it the same way. I am a diabetic and i”ll always be a diabetic. Through diet and exercise my A1c is now 5.1…six months ago i was at 9.4. While i fully intend to maintain my current lifestyle, i know that i will always crave things that i shouldn’t have and that my numbers can get out of whack very easily. So i think that just like an alcoholic and any kind of addict, one has to just take it day by day and meal by meal. Its all about choices…

  • Carol Sloan

    Paul! How did you do that? Specifically!

  • Bob Burleson

    Hello! I’m new to this forum and will ask a question I am sure has been asked before, but I have not researched. I take met’ and glipizide plus long acting Lantus insulin, and Novolog fast acting. What I am suspecting is that even with a low carb diet if I take to much of the Novolog along with eating, I am gaining weight and my FBS raises to 250+ by the AM.
    1. Does insulin cause weight gain and higher FBS readings?
    2. My a1c was 10.4 the first of this year- now is 9.1, but I am stalling out and have the holidays coming up. Will eating in moderation help with the festivities of the season?

  • Obrdl

    Amen someone smart, can’t stand when drs and nurses say once a diabetic always a diabetic, that’s a LIE,long as you don’t go back to your bad eating!!!!

  • chunk2k3

    Diabetes is a metabolic syndrome cause by Insulin Resistance, that of which is caused by a long term elevation of Blood Glucose levels.

    Fat is the only macronutrient that does not raise blood glucose levels. A disproportionate ratio of Fats, Carbohydrates, and Protein are the cause Diabetes. It is also worth pointing out that since every human on this planet is different, a blanket statement cannot apply to all of them.

    It is almost guaranteed, that even a Vegan eating a whole food diet will at some point develop diabetes; if the ratio of macronutrients are skewed to Carbohydrates and Proteins (no matter the form factor).

    We should challenge the dogma that Fat is harmful and Grains are great, not subscribe to it without asking why. Asking why would lead you to one of the many studies debunking the lipid hypothesis.

    As a side not, acute inflammation of the arterial walls is what causes lipid build up. The leading cause of this inflammation is insulin.

  • chunk2k3

    Insulin is a hormone that tells the body to store fat and glucose. When insulin is constantly in the body it sends a mixed signal that you should store everything. Weight gain is typical from what I have read.

    Higher Blood Glucose levels are normal in the morning. This is called the Dawn Effect. It is a natural occurrence as your body ramps up for the day. You release hormones before you wake up to transition from a sleeping/fasted state to an awake state.

  • David Ham

    Carol… I went from 10.4 to 5.3 in about 90 days… low carb/high fat and regular walking

  • imskylark

    Been there, done that. My diabetes got worse and I gained weight and it just wasn’t stopping. I added saturated fat and my weight gain stopped. Lowered my carbs and I actually took off the weight and my blood sugar is in normal range. My complete blood work is awesome and my doctor says to continue what I am doing. Go Butter!

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