Potatoes and delayed BG spikes

Hello all!

This is my first time using this forum! I have been Type 1 since 2009, when I was diagnosed at 16 years old. Recently, I have started to eat sweet potatoes and sweet potato fries a lot more. I noticed that about 3 or so hours after eating,I have been getting high readings even though I have been correctly bolusing prior. I typically do an extended bolus giving myself 50 % of the insulin initially then allowing the other 50% to extend over an hour. I was wondering if anyone else has an issue with potatoes causing sustained/delayed BG spikes? I know potatoes in general are high in carbs, and I account for that. What’s weird is that the spike never happens within the first two hours after the meal; it’s hours later that my blood sugar seems to continue to rise. Any advice/thoughts would be appreciated, thank you! :slight_smile:

Hi @CRWilson and welcome to TypeOneNation. Some carbs act very fast and some very slow. When mixed with fats, some carbs keep giving for up to 5 hours. How is your blood sugar from the time you eat through that first hour? If it’s good then you probably need to keep the rate the same but add units any time to your extended bolus. Of course I am assuming you make all your own insulin decisions and are comfortable with it.

Figure out how much more insulin you need and for how long and add it to your bolus plan.

Also, depending on your activity during that time you may need way less if you are more active. Good luck!

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@CRWilson Hi Christina and Welcome to this Forum! It is nice seeing your first post and I hope that what you have already read has helped you.

You and I have a couple of things in common; we like potatoes and we were both diagnosed at age 16 - me on my 16th birthday. As @Joe said, the fat absorbed when frying potatoes can extend, and in my experience, intensify the natural carbohydrate effect in a potato. For me, a baked, roasted, boiled, mashed potato will increase my body glucose level over the first hour and then my BGL [Body Glucose Level] will gradually decrease over the next couple of hours - no prolonged glucose rise - except when I overload the baked potato with delicious butter, sour cream and bacon. I find that when I eat really greasy ‘french-fries’, I need to add a bolus a couple of hours after eating - I watch my CGM graph to time and guess at the bolus amount; I’ve only recently begun using Control IQ and will report soon on how that deals with fries. In the past month, we have been using an “air fryer” at home and I haven’t noticed any “extended” BGL rise with either white potato or sweet potato.


I find sweet potatoes cause a lower my BG than white potatoes, which behave like sugar. I no longer eat white potatoes. I bake the potatoes, I don’t fry them. So the carbs affect my BG immediately. I just need less insulin for sweet potatoes than white ones. I do not get a spike later. Everyone is different, though.