Short walk causes low then high

I know this topic has been discussed many times but I wanted to get an idea of how common the low then spike occurs for a short walk.

For example, I will begin an evening walk (or run or other activity) at say around 100 and trending up. Within five minutes I start to trend down slowly at first. By the time I reach home, 20 minutes later I’m 60 and going straight down. I feel it, too! Five minutes later I will be spiking up and with 20 minutes I’m back up to 100 and heading straight up! This is without eating anything. And the drop occurs during the activity whether I’ve had recent bolus or any IOB or not.

Does this happen to others? It happens to me consistently. And really any activity causes this. It is exhausting and disappointing at the same time.


What type of shape are you in? This doesn’t happen to my son, but he is young and in shape.


I’m in excellent shape physically as a runner. When I do my daily runs, I’m more prepared taking carbs as needed along the run (learned from Eric!) so I have much more control.

This issue is more for short spurts of exercise/activities, not anything really planned.


Then I am going to tap out of ideas. My son walks regularly and only goes low some of the time. Even when starting from 80-100. Nothing that would be described as a pattern.

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Maybe it is age related or perhaps it is because I am mostly working at a computer during the day, so not very active unless I go out for a walk, etc. And my basal is set accordingly.

Mine is definitely a pattern.

Is your Loop monkeying with things while you are walking and afterwards?

Also, you said it is a pattern, but are you doing the walks at the same time of day? Like if you were to do it at a totally different time, would it also do the same thing?

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Good point. Yes, Loop will suspend insulin during a walk since I am going down. You can see that in the Nightscout image I attached. But it is for such a short time (less than 20 minutes!), insulin suspension doesn’t stop the BG drop, nor do I think it impacts the spike after the walk. Loop starts giving auto boluses as soon as it see a spike, shown in the attachment. But it doesn’t stop the spike.

Yes, usually the walks are the same time in the evening, or during the day. But, yes, anytime I do a walk/activity this same exact thing happens. :frowning: So activity really doesn’t have any benefit for me BG wise!


Might be a worthwhile experiment to turn off loop a few times and see if it makes a difference. It is a very easy thing to test out. :man_shrugging:

When you don’t walk, does this happen?

Like just to rule out that it is the walk and not anything going on with general basal needs or metabolism or hormones at that time of day.

Since you are in shape, I would not expect that it is related to epinephrine or hormones from the exercise.

But is there a stress factor involved? Like if you are going outside and need to make sure you have a mask or have to worry about sanitizing your hands or worry about being near other people?

For example, some D’s can actually spike from things like traffic. Just the stress factor.

And then the more the spike happens, the more you worry about it happening, and then it gets worse!

And then the last thing would be the possibility that it is a release of glucagon, if your body still has functioning alpha cells. In general, after a long enough time with diabetes, most T1’s don’t have a glucagon response from a low. But a small number of them still do.

Do you ever have a spike after a low, other than in the walking example?


No, it doesn’t! It is definitely the walk. But it could be any slight activity, like even house cleaning. Yes, neither feel like exercise! Certainly not like running uphill! As soon as I stop the activity, my BG goes back up. Usually higher than prior to the drop.

I don’t think it is a stress factor. I love being outdoors and do not need to wear a mask in general since no one is around. Also, no traffic in my neighborhood, but that WOULD be stressful for me! Maybe just the fact of going back indoors would cause stress. Except, this occurs with any activity, like being indoors cleaning, there is a drop followed by a spike.

No, unless, of course, if I take a carb correction which is too much. I’m not even taking any carbs for the walk low because I know I will spike up if I wait a few minutes.

I can sort of understand the low BG from an activity, but I can’t comprehend the spike that immediately occurs! It is sort of like what might occur after a run, but my runs are long, and yes, I could be ZB for a couple of hours. A walk is very, very short of 20 minutes, and even if Loop suspends to ZB for 20 minutes, would it cause such a spike? I no longer have my pre-Loop data but I believe this occurred even pre-Loop.


Can you try turning off loop for the few hours before and after, just to eliminate that variable?

Just have a solid basal, and see how that looks for the same activity. Get that as a baseline.


Yes, good idea, I will try that! I’ll keep you posted.


Kind of as a tangent to this.

For any of the systems that adjust your basal like Tandem or 670G or Loop, it is possible that a person’s settings can be far off, and they would never know it.

Like if their basal was set to 1 unit per hour, but the system keeps having to turn it off or raise it throughout the night, they might not really know how much basal they actually need. If they are not paying attention to the adjustments the pump makes, they wouldn’t know.

I think having the basal amounts dialed in as close as possible is better than just allowing the pump to make large adjustments.

Not saying that is your case. I am sure you pay attention to the pump activity and make proper adjustments to your basal settings!

This is just a comment for anyone using these systems - a general recommendation to every once-in-a-while turn off the automatic pump adjustments as a sanity check and see how close all the settings are. Or at least make a note of how many adjustments are being made by the pump.

I think this is an important suggestion, because what happens if someone’s transmitter fails or they have a Dexcom issue. If they haven’t been paying attention, then suddenly they are screwed because they have no idea what their basal needs actually are.


Good recommendation. I know my basal is not perfect as I use only one and know that I frequently trend low late afternoon because of this, but not too low, and I recover during dinner. I think AB branch handles a certain amount of basal being off. It will make a correction to bring one back into range.

I definitely have my share of sensor and transmitter failures. I agree, one should know their basal. I don’t think I rely on Loop at this point without being able to return to MDI or to the pump. It is a scary thought thought to not know one’s basal. My Loop basal is the same as my pre Loop basal which is basically the same as my MDI basal give or take .1 or .2 units.

I will be testing this out in y he next day or two!