Carb question regarding potatoes

I rarely eat jumbo potatoes but when I have glucose levels have gone high despite bolus. How many carbs in a jumbo Costco Idaho potato, the ones they sell in the bags? I bolused three times above carbs listed and still had high glucose.
Thank you!

When I would eat potatoes based on carb listed( I would weigh the potato to be exact) in most cases I was wrong too little for white potatoes and(if I remember correctly and too high for sweet potatoes.) I think this must be an individual thing. You will have to learn what is your bolus number for white potatoes based on experience. 3x above is a lot to me, what are u putting on butter, cheese or eating with it.There may be other things that are increasing the bg

I use sweet potatoes where possible. They have a lower GI then white potatoes

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I have a few thoughts about your situation with potatoes. Do you think the insulin to carbohydrate ratio (I:C) you’re currently using is accurate? Have you experimented with more aggressive ratios? (Smaller ratios like 1:5 are more aggressive than larger ones like 1:10.)

Do you prebolus? If so, how long do you wait between your insulin dose and the first bite of the potato? Have you ever used a continuous glucose monitor (CGM)? I’ve found in the past that waiting for the CGM glucose line to start to bend downward after dosing identifies a favorable time for me to start eating.

We can only control two factors with insulin: dose size and dose timing. Sometimes the standard 15 minute prebolus time is not enough to prevent the glucose spike.

As much as I loved to eat potatoes, I decided to stop eating them due to their causing blood sugar problems like you describe. With the emerging epidemic of diabetes in our population, I wonder if foods like potatoes are healthy even for non-diabetics.

I’ve made “mashed potatoes” from cauliflowers and was suitably impressed with how much they resembled real potatoes in taste and texture. They don’t stress blood sugar levels like potatoes and satisfy me.

I think you can make some improvements with glucose levels after eating potatoes by not only getting the carb count right but also using an accurate I:C ratio and allowing sufficient prebolus time. Good luck!

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I eat lots of potatoes, quinoa, rice, and legumes of all types. I eat very little fat. My A1c is 5.2.

See the Mastering Diabetes website to see why this is an extremely healthy way to eat while reducing your insulin resistance.

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My guess, it that your are seeing the effects of not just calories, but its glycemic index. Potatoes raise blood sugar rapidly, while a similar amount of carb as vegetables will take much longer, and depending on your long term insulin dosage, might have minimal impact.

I have been doing this. It is very helpful

Continuing the discussion from Carb question regarding potatoes:

Thank you everyone! You are so helpful. I generally wait 15 - 20 minutes after bolus to eat. I believe my carb to insulin ratio is correct, my endo adjusted it and my numbers are good. I have seen the pattern of spiked glucose levels when I eat white potatoes sadly… I rarely eat them. I made stuffed skin on potatoes with broccoli, chicken, cheese, and bacon for my family last night. I took insulin for 75 carbs when bag said 26 carbs per 5 ounces but I didn’t weigh the potato. Would I weigh it raw? I’m guesstimating it was 10 - 12 ounces which would have been 62 carbs which should have been ok. I probably really needed to weigh it. Thoughts??

I think a linear insulin: carb ratio may be wrong for most people, or at least for many people for at least some foods. It definitely doesn’t seem to work for me. If I’m eating a ton of carbs, I need more insulin per carb often than if I’m eating only a small or moderate amount. It may be similar to how correction rates certainly aren’t linear—the amount it takes to go from 350 to 100 (250 lower) isn’t 5 times the amount it takes to go from 150 to 100, in my experience, but more than that. So in that way, it may also tie back into the GI factor part, because if you are spiking from quick carbs, once your blood sugar is up, you also need extra insulin to bring it down beyond that just to cover the carbs. If you do a perfectly timed prebolus, it may be a less of an issue.

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Also serving sizes are often very off for things in order to make them seem lower calorie and thus more appealing to shoppers than they are. I bet that’s part of the problem. I definitely would not assume the package is correctly estimating the potato’s real weight.

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I have a suggestion for you that I think could be helpful and instructive. If you like the “stuffed skin on potatoes” recipe, I would make this meal for several days in a row. Be careful to standardize the serving size and each ingredient proportion.

Record everything about the meal including portion size, carb count, insulin dose size, insulin dose time, pump basal rates starting two hours before eating, meal time, beginning glucose number, mealtime glucose number, and every hour glucose after eating. Write this stuff down. It’s a forest and trees thing.

If you don’t get the glucose performance you want, vary one of the parameters. You could, for instance, lengthen the prebolus time and see how things change. You could then vary the insulin dose size by changing the insulin to carb ratio.

I didn’t mention this in my previous comment, but the insulin basal rate plays a key role here. If your basal rate is weak, it provides a “mushy” platform from which to launch your bolus. In this scenario, the bolus must first backfill the anemic basal rate before it can do its bolus work and then comes up short.

I would not take any endo adjustments as being necessarily correct unless you confirm them for yourself. By doing the experiment and keeping track of the results, you will identify what works for you. It’s not some theoretical ideal but your actual results.

This is a great exercise because once you perfect that meal, you can then experiment with another favorite. Eating the same meal for several days in a row is a small price to pay for reality tested results.

Things, however, will change since we’re dealing with diabetes. It is a dynamic disease and static thinking will disappoint you if you depend on it. You may need to repeat this experiment from time to time if you start to see poor results.

Edited to add: What this exercise gives you is much more than the solution to a certain meal. It gives you the tool to figure things out for yourself, a valuable asset that you can use the rest of your life. It can give you competence and confidence that is priceless!


Potatoes are challenging. I’ve never been able to pull this off via a straight carb count.
I haul out the ‘big guns,’ so extended bolus, pre-bolus, temp basal increase, taking WAY too much insulin and then anticipating that I will go low later - or some combination of these things.

I error on the side of too much insulin. So, I will almost always end up low, instead of high.

I usually don’t have a problem with plain potatoes. But as soon as I add oils/fats to it I have to make sure I cover the carbs again later.

Plain roasted/baked potatoes, I prebolus half 30 minutes before and I don’t get a spike. But I also like a purple potato that I like to drown with Earth Balance Margarine. So I prebolus a third, a half hour before, a third when I eat it and and a third a half hour after because of all that margarine. I’m thinking the cheese and bacon are the same as my margarine of higher fat that is delaying carb absorption and that is why maybe you still got a spike? By the way my carb ratio changes a lot between morning and afternoon/night.

We are all so different and @Terry4’s suggestion is really good. An endo has a set recommendation for everyone. But time of day, the stress you have for the day etc can change what you personally need. So it’s key to learn to be able to adjust as needed.

(a purple potato is just a little sweeter white potato with a little more antioxidants)

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@Terry4 and @Yolanda Basal testing may help with this.


I eat white potatoes occasionally but only certain ways. I usually only eat them when reheated (resistant starch factor) and then only eat a very small portion. For instance. 4 steak fries are my limit. 1/3 of a cup of other ways sometimes only 1/4 cup. It’s really a mind game for me and if I can just have a taste, I deal better than feeling deprived. :grinning:


Also keep in mind, re: potatoes as well with rice and pasta, the temperature of it will affect its effect on blood sugars, because if you let them cool down before eating them (like in potato salad, pasta salad, sushi, etc), some of the starches in them turn to resistant starch, which is good because it both feeds probiotic bacteria in the gut and doesn’t get absorbed/turned into blood glucose. Some of the starches will still be absorbed (most of them in my experience), but it seems to both lower the GI and the total carb count of the food to eat it that way.


Lots of great info here! Thank you sooo much!
I’m going to start another thread because now I have more questions. :blush:


I got this wonderful scale from Bed Bath and Beyond about five years ago. It’s called Perfect Portions digital nutrition scale. It comes with a book that has codes for just about everything. And it gives you a complete nutritional breakdown. I just put the potato or apple or strawberries on the scale and I get how many carbs it has. I showed the scale to a T1D mom, who was over one day talking about Clarity reports. And it was an educational afternoon, because every thing she thought she knew the carb count, was off. It is amazing how comfortable we can get with out guessing. I love the scale. I just put the bowl on it, zero the scale add the code for the food I am weighing and it’s good.
Just another tool in my little diabetes tool box.

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I have a similar scale. However with sweet potatoes, it was not accurate for me. I do not eat white potatoes so I can not say. Maybe Perfect Portions is more accurate. I do use it for other things.

Half a baked potato. The large is about 45 carbs. I have learned if I eat the skin, it will slow it’s absorption.
Of course if you eat it with some protein you also will slow it down a bit. If you like mashed potatoes you can switch out 75 percent for mashed cauliflower. It sounds awful but I really like it and now you are down to about 15 carbs for a Serving. I currently use 10 percent potato in mine but then again I don’t mind th cauliflower taste.