What time of day do you exercise? Ugh!

Hi! I’m curious…When do you exercise? When, how long and what exercise brings you the biggest blood sugar benefit? Especially all of you people with “routines” in place, is exercise always predictable for you?

I used to have a pretty good idea and pattern carved out but lately my numbers keep surprising me by creeping up when I’m exercising. The adrenaline from some things (like skiing) have always dealt me a spike but lately even a simple walk isn’t doing what it used to. I’m even leaving yoga higher than when I go in. Thanks for sharing your insights!!
Sharing an article with some Exercise 101’s below…strong text

Does It Matter When You Exercise?
How the time of day you exercise affects blood glucose
Link to full article at bottom of page

You’ve probably heard that exercise aids diabetes management. It’s true: Moderate aerobic exercise—the kind recommended 30 minutes a day, five days a week—can help you lower your blood glucose.

And exercise has benefits beyond blood glucose control, says Michael Fowler, MD, assistant professor of medicine and director of diabetes outreach at Vanderbilt University Medical Center. “[Regular exercise is] highly, highly, highly beneficial in folks with type 2 diabetes,” Fowler says. It lowers risks of cardiovascular events in people with type 2 diabetes. The cardiovascular protection is less well proven in people with type 1 diabetes. “But we know that exercise, for everybody, makes our bodies more sensitive to insulin,” he says. That includes any insulin the body makes or that a person injects. Greater sensitivity to insulin helps the body use it effectively to lower blood glucose levels.

You may wonder when to fit workouts in and whether the time of day you exercise makes a difference in blood glucose levels. Let’s take a closer look.

Around the Clock

Whenever you can move your body—a 20-minute walk in the morning or playing catch at night—it’s good for you and your diabetes, says Sheri Colberg-Ochs, PhD, a fellow with the American College of Sports Medicine. “The best time is when it fits in your schedule,” she says.

Avoiding Lows

Of course, during and after exercise with diabetes, some people face the risk of blood glucose going too low. That’s more likely to happen if you use insulin and sulfonylureas, which can put you at greater risk for lows overall.

One thing that may help you manage blood glucose during and after exercise is to set a regular time for it. A consistent exercise routine, says Fowler, can help you learn more about how exercise affects you. “What we typically recommend is that somebody does exercise at the same time—that way things are more predictable. If it’s going to cause low blood sugar, they learn how to predict it or adjust to accommodate [that].”

So let’s rock around the clock to see what you might expect with regard to your blood glucose and exercise, keeping in mind, as always, that your response may vary—from other people’s and from day to day.


Some people like to rise and shine. And this can be a good time to exercise to combat what—for some—are the day’s highest blood glucose levels. During sleep, the body typically maintains blood glucose levels by making hormones that tell your liver to release glucose. The body with diabetes often needs help from insulin or other diabetes medications to make sure the liver doesn’t produce too much glucose, which can result in high blood glucose overnight and on awakening in the morning. Plus, the dawn phenomenon—thought to be the result of a normal surge of hormones that the body produces to kick-start the day—may also raise blood glucose levels.

Non-Insulin Users: Teresa Anderson, 45, of Myersville, Maryland, fits fitness into her schedule by working out first thing in the morning. “It’s what I can stick with. That is the key,” says Anderson, who has type 2 diabetes.

Insulin and Sulfonylurea Users: Talk to your doctor about what to eat before and after morning exercise and how to adjust insulin dosing and food to avoid lows.

Before Meals

Working out before a meal can be a great way to fit in some exercise. And while you may not see as much of a drop in blood glucose as at other times of day, it’ll still do your body good.

Non-Insulin Users: If you don’t take insulin, you probably need no extra preparation when exercising before a meal, says Colberg-Ochs. “The main effect of working out pre-meal—other than breakfast—may be a slightly lower rise in blood glucose after eating,” she says.

Insulin and Sulfonylurea Users: If you frequently go low while exercising, it may help to exercise before meals instead of after meals, when bolus insulin or pills that cause the body to secrete insulin are the most active. Fast-acting insulin injected or pumped for your previous meal takes about four hours to be cleared from the body.

After Meals

Working out increases your body’s insulin sensitivity, making it easier for insulin to transport glucose to the cells that will use it. So working out after a meal can be a good way to “use up” excess glucose after eating.

Non-Insulin Users: “I test after I exercise. I noticed that my numbers were definitely lower [after working out],” says Jacquelyn Weller, 37, of Reed City, Michigan, whose after-dinner exercise helps control her type 2 diabetes. “When I saw the numbers, I kind of celebrated a little bit. It really pushed me to make sure that I keep exercising so that I keep seeing those numbers.”

Insulin and Sulfonylurea Users: Do exercise safely: Carefully monitor your blood glucose during and after post-meal physical activity to avoid surprise lows. “Generally, if you’re really worried about hypoglycemia, avoid exercising within two hours of a meal,” Colberg-Ochs says. This tends to be the time that injected or pumped mealtime insulin is most plentiful and active.

At Night

Any exercise, no matter the time of day, is a good idea. Be aware, however, that working out at night can interfere with your sleep—which can affect your diabetes. The Division of Sleep Medicine at Harvard Medical School reports that the body secretes the stress hormone cortisol during exercise. That activates your brain’s “alerting system.” If you want a good night’s rest, make sure to finish your workout at least three hours before bed.

Non-Insulin Users: Working out at night should not increase hypoglycemia risk for non-insulin users, says Colberg-Ochs.

Insulin and Sulfonylurea Users: Exercising too close to bedtime can be risky. When you’re asleep, you may not feel a low coming on. So, if you’re an insulin user who wants to work out at night, you’ll want to carefully monitor blood glucose before, during, and after exercise and before bedtime. A snack before you go to sleep may be a good idea. You’ll also want to check blood glucose in the middle of your sleep time (say, 3 a.m.), at least a few times while developing a regimen to be sure you’re not going too low. Talk to your doctor about the best hypoglycemia prevention approaches for you and your routine.

The bottom line? There’s no best time of day when it comes to exercise. Pick a time that works for you and just do it. As Cynthia Zuber, 39, of Minneapolis, has found, consistency is key. She prefers to walk after meals, but the timing is less important than doing it nearly every day. “For me, a walk is the perfect balm,” says Zuber, who has type 1 diabetes. “If I walk three miles a day, diabetes is so much easier to manage. I always try to get that movement in.”

Anaerobic Exercise

Different types of activities will affect your blood glucose in a variety of ways. We’ve already talked about aerobic exercise, but anaerobic exercise, or strength training, can increase your adrenaline, and that can raise your blood glucose. The same goes for interval training, including workouts such as CrossFit, and activities with short bursts of intense activity, such as basketball or hockey, says Jen Hanson, RKin, MEd, a registered kinesiologist and executive director of Connected in Motion, a Toronto nonprofit designed to get people with type 1 diabetes involved in adventurous exercise. Hanson, 31, lives with type 1 diabetes.

“When you’re doing activities that are anaerobic, with short bursts of energy, the body is releasing large amounts of adrenaline,” Hanson says. “That signals to your [liver] that it needs to dump large amounts of sugar into your bloodstream. Often then you’ll see spikes in your blood sugar.” This is because anaerobic exercise prompts your liver to produce glucagon, a hormone that raises blood glucose levels. When your body is being pushed to its limit—not with gentle or moderate exercise, but real heart-pumping, high-intensity stuff—its “fight or flight” reflex kicks in. “Your body doesn’t want you to go low,” Colberg-Ochs says. So instead, it signals your liver to kick out lots of glucose so you have energy.

“Usually, the spikes in blood glucose following high-intensity work come down on their own within a couple hours in non-insulin users,” Colberg-Ochs says. “It can help to follow such activity with a lower-intensity cool down.” Insulin users, she says, should talk to their health care providers about whether or not to take insulin to correct post-exercise highs; if you take too much, you’re likely to come crashing down later.

Safety Note

Talk to your doctor before making any big change in your exercise plan.


When I bike commute–about a 25-30 min. ride each way, middling-to-strenuous–I see almost no BG drop in the morning commute and a pretty substantial one in the afternoon. I’m guessing it’s a case of residual dawn effect in the morning versus residual insulin from my lunch time bolus in the afternoon. Even though the insulin is supposed to be cleared by evening, I’ve noticed that if I have a no-carb lunch I can start off my ride at 120 or less and still be ok (above 70) by the time I get home. Whereas if I’ve had to bolus for lunch I need a much higher BG for a safety margin, like 140 or so.


I don’t go to the gym for exercise but love country hikes and outdoor chores. I avoid physical activity right after meals, i.e. when I still have rapid insulin on board because it brings on ‘false lows’ for me (lows that don’t need correction because carbs from my meal are still being metabolized). So I wait two hours after my most recent Humalog shot before physical activity. Being on MDI, I make sure to carry a fast sugar in my pocket, too. If my exercise is strenuous as it was this week where I moved a pile of rocks, my BG climbed a bit but if it stays under 8 mmol (~140 mg) I am ok with it for the time of the work out until my next meal, then I correct it down.


I find that there’s a bounce-back from exercise in general. I always try to give it some time to recover after a ride, unless I’m really getting hypo-symptomatic, because it usually comes back 20 points or so on its own.


Thanks @DrBB! This was super helpful and almost what I was looking for!! I just got into cycling in January and can’t pin down my digit trend yet! Casual rides on my cruiser used to drop me almost like clock work at 20 minutes. I am spiking pretty soon into my road bike rides. Must be the adrenaline and probably still the nerves of road biking…
Thank you!!

I’m a runner and still trying to figure it out. Seems like right before lunch or right before supper is best. However sometimes it’s just still too hot out in the summer at those times
Would like to switch to first thing in the morning but I also take lantus in the morning to keep my schedule consistent

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Have you ever lowered your basal rate 1 - 2 hours before your ride home?

I am doing a lot of cycling in preparation for my cross-country trip. I have been finding that lowering my basal to 10% at least 1 hour before and during riding has been really helpful. In addition, I have recently been experimenting with eating some protein before my rides, as well as a protein/electrolyte drink mix every 45 minutes. The jury is still out, but my last 4.5 hour ride was a virtual flat line with a low of 73 and a high of 136.

My rule of thumb is that the time of day doesn’t matter, but the type of activity does. Most of my exercise is aerobic, not anaerobic. So I typically start by lowering my basal rate to 50% and make sure I have my glucose tablets available. If my BG is anything below 85 and the CGM is trending flat or down at the start of exercise, I will lower may basal rate even more, maybe down to 0% and or 2 - 4 glucose tablets and/or a glass of milk.

If I am doing an anaerobic exercise, I will still start with a lower basal, but then I move to a higher rate of up to 150% 30 minutes before the end of my workout.

At all times, I adopt a pretty fluid approach based on what my finger-sticks and CGM are telling me; what my trending was before the exercise; what and when I have eaten, etc. There is no exact formula in my experience.

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Yes–I actually have a reminder set in my phone for that. But nothing seems to work nearly so well as just going zero carbs for lunch and not having to bolus at all.

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Hi! How many miles/minutes in are you before you notice your bg starts dropping? Thanks!
Way to go on that flat 4.5 hour ride line! Whoot whoot! I bet that felt great! I really appreciate your insight, I am also training for a ride and am such a newbie!

Typically I start to drop about 30 - 45 minutes into my rides. I also typically start out at a much higher BG range (175 - 225) because I know I will come down into range, plus the amount of time I spend “high” is pretty minimal as a result of the exercise.

Right after breakfast works for me and my blood sugar control is way better if I get at least 30-45 minutes of moderate to vigorous exercise. In my case this means hiking or trail work for 3 seasons and cross-country skiing during winter. Just enough time to cram it in before going to work!

I walk dogs for a mile, then I play tennis for 2 hours 3 days per week. the rest of the week I go to the gym after walking the dogs. I found BG going higher after I exercise, so I had to actually add a good amount of carbs. 40 carbs per meal is what i need or my liver pushes out glucose. Dr says that it happens lots. i also walk dogs for a mile after lunch. My high time is always as soon as I wake up. usually 130 or so. if I do not eat enough carbs, I will go up to 170 after I exercise. If I have an english muffin with eggs or two pieces of toast before I exercise, I am at 105-115 before lunch. I am on Lantus pen 50 units at night before bed.

Always in the morning. I drop my basal an hour before and the hour during I’m at the gym. Sometimes it’s weights and other times its cardio. I usually check right after to make any corrections. Unfortunately, I have a hard time seeing trends. So sometimes I’m high and occasionally I’m low.

I exercise when I can, often afternoon, sometimes evening. If I have insulin on board then there’s always a problem (lows), so I can’t bolus much if any before exercise. XC skiing (skate skiing) makes me drop about 100 points in 20 minutes so I have to get my bg up there before starting, turn off basal an hour before, no bolusing… not sure how to deal with that! other strenuous exercise also makes me drop (usually, not always!), but then I will go up as soon as it is over, so usually have to bolus post-exercise (which could also be due to decreased basal rate during exercise). Day-long hikes are also a challenge. Well, everything is a challenge. Not sure why I can’t figure it out, even after 17 years!

Yes, I feel the same way, everything is a challenge! I run usually mid morning once my breakfast is mostly digested and glucose is stabilized. I usually have issues with lows not highs, but on occasion I will go high, why, I still don’t know! If my bg is trending low I will eat a small banana before my run. If it is trending high I will only eat half the banana. I always bring 4 glucose tablets along with water on the run and sometimes end of taking 1-2 before the end of the run. This occurs probably about 25% of the time. I’m experimenting with basal reduction of 20% during the run to see if I can reduce the lows. I worry this will cause a high though. So far it seems to be working with my bg dropping only into the low 60s or 50s. I also experiment a rebound like DrBB, with bg going up at least 20 points shortly, within the hour, after the run. But this doesn’t always happen. I’m not sure why??

I often exercise at the after which, i am able to get enough rest to heal my body and muscles.

I usually exercise in short spurts 3x per day doing some combination of flexibility, weight lifting, and cardio. This program works better than setting a specific time every day since I usually sit on my butt all day. :laughing: (Oh, the joys of online work, blood sugars, and long days!)

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Welcome to TUD @Crimson_Sugar! That sounds like a reasonable way to manage things in the work-from-home environment. I got laid off due to COVID back in April, and since the weather has been mostly favorable where I am, the upside has been I’m getting in way more bike riding. Had a tele-visit with my endo in May and she told me I’m her only patient who has actually lost weight since the pandemic lockdown started.

Cheers, hope you stick around!

I tend to exercise after breakfast and sometimes in the evening after dinner. I exercise >30 minutes and as long as 3 hours.