Working Out BG Spike

I have been doing crossfit for about 8 weeks now, feeling great.
I am having trouble with my blood sugar spiking after some of my workouts.
I haven’t figured out a patern yet.
Does anyone have any history or insight they might share on this.
I normally have 15 to 20 carbs prior to workout and disconnect from pump.
It has happened 2 times in 8 weeks.
I am working out first thing in the mornings.


There are several possibilities.

For many people, their BG will rise first thing in the morning. As they go from sleeping to moving around, their liver releases glycogen to provide fuel for the body. So working out early in the morning can be part of the reason you see a BG spike.

Part of the spike can be from intense workouts. When you put sufficient physical stress on the body, your body releases stress hormones (epinephrine (adrenaline), norepinephrine, and cortisol). This is used to help your body handle the stress. The release of the hormones increases the release of glucose by the liver. Your heart rate goes up, more oxygen flows to the tissues increases, and liver glycogen stores are released for fuel. You’ve heard of the body’s “fight or flight” response. That’s part of what can cause a BG spike - fuel to fight or flee. Your liver is releasing the fuel. But this generally only happens when you exercise as sufficient intensity.

Disconnecting from the pump you are reducing your body’s available insulin supply, so that contributes to it as well. When you say “disconnect”, are you actually physically removing the pump, or just turning it off? Are you able to leave the pump on and just reduce basal?

Since you don’t always see it, is it only with intense workouts? When you are very tired at the end?

What is the typical pattern of your crossfit? What type of exercises do you do? I assume a general easy warm-up, followed by various other activities? Is there any pattern to what you are doing?

How long is your workout, and how long are you disconnected?

Side note:
Generally, easy to moderate workouts will cause a drop in BG. Usually it will happen early in the workout as your body goes from inactivity to activity. Once your body has been moving for a while, a lot of the fuel for the activity is provided by muscle glycogen, which does not affect blood sugar at all. That’s what makes muscle glycogen great for us diabetics. It lacks the glucose-6-phosphatase enzyme, so it is not able to pass glucose into the blood! But it takes a while for that energy system to be enacted, so you may see a drop early in the workout before it is engaged.

1 Like

For the most part I have been ok with the morning workout, my BG is typically 120-140 in the am and I usually do 15-30 carbs like apple and peanut butter.
Yes I am disconnecting, I do the same when I do my 3 mile run a couple days a week.
I can try the reduce basal %

It seems like all of the workouts are intense with exhaustion at the end???

typical day is
warm up and stretch 10 to 15 min.
go through work out with no weights to check form.
then 15 to 30 min of high intensity
disconnected up to an hour.

Does eating more carbs before workout have an impact on the fight or flight release on glycogen?? With appropriate amount of insulin??
Does active insulin play a role at all??

thanks for your consern.


For stress hormones, eating more carbs won’t affect it. Your body releases the stress hormones - epinephrine, norepinephrine, cortisol - and your liver responds with glycogen for fuel. It is just assumed your body will also release insulin for the fuel. But that is the part that is broken.

If you are starting at 120-140, and you have a snack, what do your BG’s generally run when you are finished?

Yes, any insulin will reduce it. Do you have any IOB when you start?

Depending on where you usually end with your BG, possibly you can wait until after the warmup and stretching to disconnect?

I don’t have much history yet for the type of workout in the am. but I would say that I am typically fairly normal. I have only noticed the two instances where it was close to 400.
I come home and have eggs and or a protien smoothy thing. I am starting to watch closer and starting a log with more specifics, about my day.

I would say that I have little to no iob when I work out in the mornings. Just what my basal insulin is giiving me. which is at 1.2 u/h at that time.

and i typically will not take a shot for my small amount of carbs, if my BG is in the normal range, fearing the lows.


There is a fairly consistent heart rate and duration that you might see a spike. It varies for each person, based on their age and fitness. But for each person, it is probably a very consistent number.

For example, you may find that 30 minutes of a 150 heart rate causes a spike. It might be more or less, but at some point, you can start to figure out what workout intensity is enough to trigger your liver to start saying, “Rich’s heart rate tells me he is in trouble, I need to give him fuel…”

Do you do heart rate monitoring when you workout?

There’s great information shared here! Thank you @Eric2!

An additional resource I’ve heard about, I have the book, but have not had the opportunity to read it yet, is “Diabetic Athlete’s Handbook - Your guide to peak performance” by Sheri R. Colberg, PhD