Low During Work Outs!

Hi Type One Community:

I am really struggling.

I’m 26 years old and have had T1D for 17 years. I wear the 670G Medtronic pump with the Guardian Sensor, and I’ve always been very active- it’s a big part of my life. Getting a low blood sugar during or after a workout is definitely something I’ve experienced. But recently, I feel like I can’t move my body at all without having my blood sugar drop.

When I go on a brisk walk for 10-15 mins, it drops. If I dance, do a HIIT workout, yoga, kickbox…it drops. I usually workout after lunch or after dinner, so I have carbs in my system. If I know I am going to workout I will not even bolus all of my meal.

If my blood sugar is below 120, I’ll drink juice, have a spoonful of peanut butter and wait for it to come up. If my blood sugar is high, and there is barely any insulin on board, I’ll try to workout for 20-30 mins…but it still drops quickly and drastically.
If it’s high and there is insulin on board I wait to work out.

I feel like my body is extremely sensitive to exercise all of a sudden…have you experienced any of this before? I am feeling defeated and need your help.

When do you workout?
Do you eat before? What foods?
Have you tried “fasted cardio” or working out first thing in the morning?
Is there a setting on the pump that might help?

Any advice is appreciated. Thank you :slight_smile:


Hi @mdrsinger it’s great to hear that you are moving and exercising. So I have to make sure I have no insulin on board after a meal and I have to be sure my basal is off, or nearly off for45 minutes You have a feedback pump. What kind of prep are you doing? Are you setting the pump to manual or do you set it for exercise or for the high target before exercising?

Hi @mdrsinger and thanks for writing in. I use Tandem/Dexcom - not Medtronic - and I’m in the process of upgrading to their closed loop system which I understand is parallel to Medtronic’s, but I haven’t started yet (hopefully next week :tada::tada::tada:). I’m still using the basic pump and CGM features and I do find it doesn’t take a lot for my numbers to drop, although not as dramatically as yours sound like they do. A couple of thoughts come to mind, although you may have already considered them since you’re experienced with diabetes:

  • It’s not unusual to need to change settings now and then - be it a basal profile, carb ratios etc. And if your system has a profile for exercise you may need to tweak it.
    *You might check in with your nutritionist to update your workout/low BG snacks.
  • I’m just wondering if your insulin formulation has changed, or if perhaps you’re taking a new prescription (diabetes or not) or a different dosage of something ?
  • Some Rxs, as well as OTC meds or supplements, have the side effect of lowering blood sugar even though they are not for treatment of diabetes.
    Wishing you the best in solving your mystery.

Hi Madeline @mdrsinger. I’ll answer “yes” to a couple of your questions, and “No” to your query if the pump you are using, the 670G, has a programmed exercise setting; at least I don’t think so, and I haven’t used that pump.

What I have done, so that my pump performs the way I like during exercise, is to create what I call “Gym” Profile / Pattern. Background, following lunch [65 grams carb, usually], I get on my bike and ride three miles to the gym, my warm-up, and then do 90 minutes - two hours resistance training, then ride home - often by an 8 mile route. for this particular “Profile”, my basal begins to decrease [from my usual Basic Profile" beginning at 9:00 AM, and my bolus:carb ratio for lunch is also decreased. My afternoon basal rates are set at the lowest rate possible.

For me, “resistance exercise” affects me significantly 4 or 5 hours later, so my supper insulin: carb ratio is also lower than usual and my evening basal rates are also “reduced” until 10:00 PM. I came upon this method after much trial & error, but it now works well for me. My “big” trial is remembering to select the proper Profile [the Tandem name for Pattern] anticipating what my day will be. I also have Profiles built like thin in my pump for a day of bike-riding, and also for days I volunteer on building/repair crew.

Keep in mind, Madeline, that each of us is different, and what works for me, may not help you. Good luck experimenting.

Thanks for your reply, Joe. I also do not workout with insulin on board. Before I exercise, I suspend my pump, and then I disconnect completely when I am actually moving.

I appreciate your response. None of my medications have changed, so I’m pretty sure that’s not it. However, my settings might need adjusting.
Good luck with the closed loop system!

Hi @mdrsinger Madeline! Even basal insulin (essentially basal rate from the pump) is active for 45 minutes. are you suspending early enough?

Thank you for your response. I always suspend my pump before I workout and then disconnect completely while I’m moving. I’m thinking my basal settings need to be revised. Sounds like a lot of this is just about trial and error…thanks for your help!


Thanks! I wish you the best with adjusting your settings. Generally I’ve found that small changes make a big difference (even a tenth of a unit for me) but it does take some trial and error - especially I think when exercise is involved.
I have a phone appointment with my endo this afternoon - have been waiting to connect with her DNE to set up training - which she said was to walk me through inserting the new sensor. But I think I can manage that on my own with reading and the help of those wonderful YoutTube videos, if it comes to that. Looking forward to starting in the next few days!!!

Madeline @mdrsinger, one of the most difficult things about insulin - at least for me -, is to actually know “insulin on board” or “active insulin”.

I’m not aware of any way, other than trial & error and acute observation to know the length of time that insulin remains. This even applies to the 0.2 units per hour my pump infused into me an hour ago; my T&E has told me that some of that insulin is still working trying to balance my glucose levels. Insulin that was infused, or injected, keeps on working for some period of time even if/when a pump is suspended of completely disconnected.

Hi Madeline,

In my experience, as you noted, IOB is the biggest predictor of a low when doing rigorous workouts. Here is the thing to think about – perhaps your active insulin time that is programmed in to the pump is inaccurate such that it displays an IOB of 0.0 (or something very small), but in fact you have much more active insulin in your system. To change this (under your endo’s care, of course) on your 670G (which I have too) go to Options, then Delivery Settings, Bolus Estimate Set Up and then finally Active Insulin Time. Your time might need adjusting to account for how long insulin stays in your body, as in the pump is displaying no IOB but you actually do in fact have active insulin. Good luck to you. Drew

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I also use a 670g and the guardian sensor. I started playing pickleball for two hours at a time earlier this year. I found that eating protein only (2 eggs) before I played without bolusing and starting a temporary bolus 30 minutes before I played worked best for me. I stopped the temp basal when I had 30 minutes left to play. I also learned that my glucose levels would rise after I finished, although I’ve read for many people, they continue to stay low.

Hi Madeline I have been using the 680 for about a year and a half. Your comments actually sound like mine until a about 6 months ago. If I anticipate having a strenuous exercise I generally will eat about 30 carbs . Handful of pretzels or something before I start and don’t bolus for it. I will then attempt to watch the pump and have granola bars as necessary depending on the readings. If my sugar is still at 160 or above when I have less than 30 min6of exercise left I will will first turn off temporary mode and then maybe add a bolus to bring it down . Depending on how much insulin is on board. The 670 is a tricky thing to work with. I you like I can help…

Hi Madeline,

First of all, I’m so sorry, that is super frustrating and yes, I have experienced similar issues. If you know when you are going to work out, try to reduce your basal maybe an hour before you start your workout, you can even suspend it during a workout. I sometimes will run in the morning but try to at least have a couple of spoonfuls of yogurt or a few sips of a smoothie. You want something in your system so your body doesn’t go in to ‘panic mode’. You certainly don’t want to workout when you’re high because then you have no energy. It’s a fine balance and not easy to find. I would start by seeing where your blood glucose is and setting basal at maybe 60-70% if you sugars are in range. You can adjust that according to what happens during and after the workout. Unfortunately, if you are anything like me, nothing stays the same even if I am doing the exact same thing every day. I’m assuming you carry a sugar gel pack or something that you can easily take if you crash while exercising? I would certainly start using the ‘suspend’ setting on pump. And if you are this active on a regular basis, you may need to adjust all your settings. You’re endocrinologist or pump specialist should be able to help you with this. Good luck!! Keep us posted.

Different types of exercise trigger different types of insulin/glucose/hormonal response. Low intensity long duration exercise is a lot more likely to lead to a low blood sugar than high intensity burst exercises (like weightlifting).
My advice is keep a journal and track the following: sugar level before workout, what you did for a work out (length, intensity, cardio/lifting), sugar level after. Everyone’s body is different though, so that is why it is important to test and test safely.

Hi Madeline,
I just started using UCAN workout energy powder (https://ucan.co/product/workout-energy-tub/) before I workout and I have not gone low during a workout since! It claims that its SuperStarch formula provides steady energy overtime to prevent blood sugar spikes and crashes. I drink it 30-45mins before I workout without bolusing for it. I also start a 70-80% temporary basal about an hour prior to exercising. It also helps to make sure you don’t have any insulin on board. Before using UCAN, I found that working out when I wake up, usually around 7:30 am, helps because your blood sugar naturally rises at this time. Hope that helps!

@mbrush Other than not taking a bolus for at least five hours before a workout, assuming a rapid-acting insulin is being used, how else can one be sure that there isn’t any “insulin on board”? Even the basal insulin, with a pump set on a temporary basal rate of 70 - 80%, assures that there is some IOB.

Does your UCAN substance somehow remove insulin that has been infused or injected? Miraculous!

Hi Dennis,
I apologize if I was too vague. By insulin on board I am referring to insulin from a bolus, not basal. For me, insulin usually stays active for about 3 hours. This is just what has helped me, but I am not a medical professional and this may not work for everyone.

Thanks @mbrush. I was really curious; over the decades I’ve been using insulin, I often wished that there was some way I could “take back” insulin when I had second thoughts about amounts I’d injected.

I began counting carbs and experimenting with MDI in the 1970’s before digital glucose meters and many times I realized that I took too much insulin. And I still make foolish mistakes.

I took tried yoga a couple of years ago and enjoyed it. I find that most exercise lowers my blood sugar so I plan ahead and cut back my insulin (I use a pump) and have a snack in advance. And of course I do keep something nearby just in case - there’s juice in my bottle rather than water, and I keep some Clif Bloks gels on me. You may have to experiment to see what to adjust and how far in advance.