After 33 yrs with Type 1 I think I must be cured because I use so little insulin

Urgh!!! In the winter I do a lot of my exercise inside but once the weather gets warm, I’m outside. This year I decided to run instead of riding my bike. All good there. My formula works pretty well. In the last 2 weeks I switched over to bike riding and all hell has broken loose. It doesn’t matter what I do, I’m low. For example: yesterday I left my house with a bg of 350 (definitely not my norm but I did it purposely). I unplugged my pump and ate 45 carbs before I left. 30 minutes into the ride I had to eat another 55 carbs. That got me through the bike ride but my Dexcom was beeping as I was pulling into my driveway. Now granted, I’m riding for 1 1/2 hours and it is mostly hills so it’s strenuous. Today, I left with a bg of 150, ate 70 carbs before I left and unplugged. My Dexcom was beeping 10 minutes into it and I gave up because I didn’t want to eat any more glucose. I don’t want to eat a crapload just so that I can ride and I don’t want to let my bg go to 500 to start either. When I hike I often go 4-5 hours without my pump on and still have to eat an energy bar but I seem to be pretty stable for that. I use so little insulin (about 20 units per day) but I’m very active and eat really healthy. Any suggestions would be super appreciated. Susan

What time of day is the exercise and what types of food have been taken in up to that point?

For me at least, in a general sense I’ve found proteins and vegetables to bring a certain stability to the blood sugars along with not getting too hungry. As for exercise, I generally will start with a normal number and if the exercise is strenuous have a bit of carbs at the beginning…one example would be 7 sips of mango juice and a honey wafer cookie if it seems like the number is on the verge of dropping. Other times, I’ll wait for the number to start dropping then bring out the carbs. All in all it seems like this has worked lately but I know I still have a lot to learn.


That would be an incredibly fast drop if it were me. 10 minutes would mean just two, 5 minute readings from you 150 BG reading! Are you sure your Dexcom is accurate? The “beeping” indicates a low of what BG? Like @MarkP, I usually start my run with a normal number, rarely anything that is high. I always carry gels and juice with me and almost always end up drinking the entire 10oz of grapefruit juice over the course of the run if I start to drop. Strenuous biking is totally different from running though so it may not work for you.

I am exercising at lunch. 7 sips of mango juice and a honey wafer cookie would do absolutely nothing for me.

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My Dexcom is accurate. I check it against a meter maybe once a week and they are within an acceptable range. I have it set to alert me at 70. I do tend to drop quickly for some reason. I just started with a new pump (770G) yesterday. I was thinking that perhaps my old pump was giving me too much insulin. I did check the totals though and they seemed to be accurate. Regardless, I moved to the new one and am still having the lows. I even reduced my basals when I put the figures into the new pump.


Something I learned from @Eric is that it important to have 0 IOB when starting a run, or take carbs to compensate for the IOB. You may already know and do this. You may even need to reduce your basal ahead of your biking. I rarely need to do this for running but @daisymae does for her swimming.


Did you have any IOB when you unplugged the pump? No IOB and disconnecting or suspending some time further ahead to “use up” the insulin in your body before starting exercise may possibly help.


Are you turning off your basal, or using an algorithm on your pump?

Turn that thing off! Zero basal. If you use an algorithm, it may see that your BG is high, and keep giving you insulin.

And as other’s have mentioned, zero IOB is gonna help a lot.

Also there might be site issues or a pump issue. If you have a site that is overused, it may delay the insulin absorption. So you might be getting insulin absorption for a longer time than what you are expecting.


I’ll be very interested to hear what works out. I suppose my body is a bit different. For me at least, it seems like in general exercise doesn’t drop the number that much but I’m more sensitive to carbs. However, if I am in full rigorous exercise mode (100 percent effort as opposed to 90) it seems like I can have a ton of carbs during and after to no effect. However, these sessions are the exception rather than the norm.


@HippieNerdBabe What kind of basal rates are you pumping at in the hours preceding your exercise outings?

Also, are you on a low carb diet or would you consider yourself fully “carbed up”?


20IU/day isn’t low if you have insulin production and maybe isn’t low on a real keto diet (less than 50g/day in my case). I’m sure I make only small amounts of insulin, if that, but my 7 day average has been 28IU/day. My long term (many years) assumption is 24IU/day.

Get a C-peptide test; that’s what I’m trying to do. I was diagnosed as autoimmune at the start of 1972 and nothing I’ve seen sense has suggested otherwise, but that doesn’t mean that my body can’t start regenerating some beta cells (unless anyone has an authoritative reference otherwise?) Those cells are, for sure, going to whack out due to overload unless they are in an exceptionally well maintained environment, but these days we can do that.

So maybe some of us can start producing most likely small amounts of insulin, but the only way to tell is with a C-peptide (which, for fully developed T1s, is actually accurate.)

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I have had 3 C-peptide tests in the 30+ years of having Type 1. Every new doctor wanted to have one done. My body is not making any insulin at all. I am on a somewhat low carb diet, however it’s more like a low fat diet (gallbladder issues) but I steer away from many different carbs because so many foods have fat in them. I am currently trying to adjust my basals to see if that makes a difference. I like the 0 IOB idea. I’m sure that I have some when I start. I will make a concerted effort to have 0 prior to my next bike ride (on Monday).


I think that this is a point of danger; the Loop definition of 0IOB is not even remotely justifiable. We all need IOB; insulin that is in our skin waiting to get into our blood stream, but the loops calculate IOB as that insulin minus what our stated basal requirement to date is.

This is why we can have negative IOB.

Zero basal, well, that’s completely different; my AndroidAPS loop is giving me zero basal for quite a lot of the time, then correcting with SMBs. I do intermittent exercise throughout the day so my body is a moving target, worse than UAMs!

I used to manage this by a carefully selected long acting basal (so my insulin sensitivity had to go up significantly to cause a problem), not bolusing before exercise and always having carbs on hand.

Looping is different; the BGs are much more stable, the insulin is much less so; my basal jumps from 0 to 1.8IU (the limit) and the SMBs add up to .2IUs regularly, many times a day. All the same my total insulin delivery is the same; the basal is unchanged, the bolus depends, of course, on carb intake but my IC is pretty much unchanged.

The amount of carbs extra I need for UE (Unexpected Excercise) is a few grammes; the Loop algo is buffering the rest from reduced (eliminated) basal and no SMBs.

Of course it only works for me; my daily life is entirely unpredictable but it does involve exercise, just no prediction when. If I don’t get exercise I’ve had enormous problems in the past, for example any driving by car beyond 30 minutes was always a major source of highs. With the loop things are a bit better, I’ve been able to drive 60 minutes without going high, but I’ve yet to try longer trips.


Success! I went for a 2 hour bike ride today. I suspended my pump 15 minutes before I left, was 250 & had 0 IOB. I actually did 1 extra hill, which was a bonus. I was 117 when I got home. As we all know, things change on a daily basis but I’m going to try this combination going forward.


What do you eat in a sample day?

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I am finding exercise a nightmare on my Tandem. My numbers sleeping and rising are great, but I go low every single time I exercise. I think it’s because it’s not clear (to me) how much IOB I have now that I’m getting different basal rates as needed auto through Tandem. The other day, I went on a bike ride, started at 17.6, 30 mins later I had a low so stubborn I had to sit on the side of the path and slowly ate 30 glucose tabs before it evened out. I had another low a couple hours later. I was in activity mode 1 hour pre bike ride. It’s so annoying to get better numbers if I don’t exercise, because where’s the motivation to move? I love being outdoorsy and athletic, and honestly am scared now when I’m alone.


Are you using exercise mode? My trainer suggested to start exercise mode 30-40 minutes prior to beginning a bike ride.

Edit I see you mentioned activity mode, sorry.

How were you getting insulin prior to the Tandem?


Wow, that was a bad low! Glad you had plenty of glucose tabs! I carry gels (anywhere from 12g to 21g depending on the gel), plus juice (around 50g) whenever I exercise outdoors. Juice works really fast for me. Just one small sip will correct a severe low for me. And yes, I still get them if I’m not diligent, even sometimes when I am diligent! Is it possible for you to carry those with you on your bike/other outdoor activity?

Wow, doesn’t Tandem show how much insulin you have onboard? That would be incredibly hard if you can’t see that! I’m on DIY Loop which shows IOB. I know if I have some insulin on board when I start a run that I could go low within a mile or less if BG is already in range. I, and I think many, have increased insulin sensitive during exercise, so even a tiny bit can really be much more powerful than if we weren’t exercising! It is tricky to know how many carbs to take to compensate for the IOB but at least it is a known risk factor for a low! I don’t know if there is a way for you to calculate the IOB yourself, if Tandem doesn’t show it that is. Maybe other Tandem users would know??

I know, for me, too, exercise is key to keeping my BGs in range and maintaining good insulin sensitivity!


If I understand correctly IOB on Tandem only shows bolus. You can see the Basal as a graph on T:Connect Mobile app. Here’s a screenshot, my basal rate is 1.1u per hour you can see where it is less and it can rise above 1.1u. The blue drops are bolus for meals, well the .84 is a correction.


@CarlosLuis Nice graph!! So in the screenshot, you took 2.5 U at around 5 PM, and at 6:15 PM, about an hour later, you used up about 50% of that bolus, with 1.28 U IOB. Does that seem right?

Here is another conversation on FUD discussing Tandem IOB and gives a nice graph of the IOB absorption time. It shows insulin is absorbed over a 5+ hour period, with 50% absorbed only after 3+ hours, with about 20% of the insulin used in the first hour. Maybe the Tandem algorithm in considering bolus, together with other criteria as well, in their IOB calculus? Your basal was reduced during this same hour, so that could play a role as well? If you used 20% of your bolus (typical for insulin absorption shown on the other FUD conversation graph) during this hour, you should have about 2.0 U IOB. Maybe the Tandem subtracts the basal that you did not receive (from your programmed 1.1U) due to the algorithm reducing the basal? So that your IOB is 2.0 U minus basal amount you did not receive (eg., 0.7U)?

@beans_betes Do you have the T:Connect Mobile app? It looks very useful!

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