My story of a colonoscopy + clear liquid diet + out of range

Some may see the following as TMI (too much information). If so, I apologize. But, I thought that some might gain something from my experience. Part of this is a rant on what I see is the ill advised high carb clear liquid diet and prep for diabetics, especially those on MDI. I was not particularly as insulin sensitive as usual, perhaps that was from not taking Metformin, or maybe from a bit of stress thinking about it. Here’s my story.

This morning I had my 1st colonoscopy since graduating to MDI as a type 2 DM. In the past I had no problems with managing good BG levels. Not so good yesterday. My time in range has been perfect for nearly 180 days. No real highs with the odd, barely lows at night (63-65mg/dl).

Breakfast consisted of 1 cup apple cider, 1/2 cut Jello, 1 cup Gingerale and chicken boullion for a total of 94 grams carbohydrates. I reduced basal by 40% and bolused 6u which should’ve been enough. 20 minutes and BG spiked to 161. I started pedalling on my DeskCycle., BG peaked 25 minutes later at 232mg/dl. After 70 minutes of spinning BG dropped to 155mg/dl and continued to drop to 77mg/dl by lunch.

8.3oz of Miralax was to be mixed with a half gallon of regular Gaterade. That would be 100g of carbs. I decided instead to do half no sugar and half regular for a total of 50g. I had to drink 8oz every 15 minutes. I bolused 3u, by the 3rd cocktail BG started spiking hard. I got back on the pedals, getting off only to drink more and a quick trip to the toilet. 63 minutes, peaked at 172mg/dl. At bedtime, dropped to 103, ate 8 grams of glucose, and went to sleep, woke up with 103mg/dl.

I was thankful for a nice gentle DP and FOTF. Was at 130mg/dl when the procedure started and 129mg/dl at the end.

Everything good but, one polyp removed, waiting on the biopsy.

Who would advise taking a high carb liquid to a diabetic for colonoscopy prep? There are low to no carb preps available at Walgreens and other big box pharmacies. Magnesium citrate with sucralose mixed with sugar free drink. I think I must be missing something here, but I have not had any BG issues before or during may last few colonoscopies.


The problem I see is not the prep as I could mix it with sugar free Gatorade. It is more the clear liquid diet. One could consume all no carb stuff like sugar free Sprite and Jello if there is such a thing, but there are no calories for the whole day. Basically a fast day until after the colonoscopy. This might cause a hypo during the procedure.

I really think there should be a better way, but no clear liquid diet I’ve seen allows for any fat or protein.

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Maybe this does not affect me because I am OMAD (eat 1 meal a day at noon). Normally diabetics are scheduled for colonoscopies first thing in the morning and that is the time BG is rising so hypo is not an issue for colonoscopy. I am also MDI. And yes, you can also fast for 24+ hours and that should not cause you to go hypo unless you are taking too much insulin or other medications during fasting period. If I fast for 72 hours, for example, my BG stays rock-solid steady at 78. The hospital is not happy if I do that as they want to see my BG over 100 but when I explain to them it is my normal fasting range, they accept it.

We are not all the same. What works for you may or may not work for others. I had no problem when I was one Metformin and Lantus, but things are different for me with Humalog added to the mix.

Metformin and Lantus create Hypos - Humalog does not as it is fast acting and mostly out of the system within 2 1/2 hours. The only way to get a hypo with Humalog is to take too much of it and yes, then you can go Hypo within an hour or so.

I had to do a 2 day prep. I used sugar free Gatorade with SuPrep. Yes I had to drink all that liquid for 2 days. But I am cleared for 5 years. I kept my pump on and managed the sugars with Italian Ice clear popsicles. I had apple juice ready if I needed it,


I have coloscopy schedule in about two weeks. I bought some cane sugar cubes (no coloring) to use in case of hypo at the no more liquids stage. If needed, the sugar cubes are OTC anti hyperglycemic.


I have been putting mine off for a few years. Finally i was cornered so I have one in 2 months. the anesthesia worries me a lot and my sugars worry me.

I will keep my pump and dexcom on so at least i will have it there to turn off my insulin if I go low. I depend on it a lot more since i’ve had it. I allow myself to go into the 70s at night, knowing it will be corrected automatically.


I had a colonoscopy not long ago and had no troubles. I had sugar free jellos and drinks. Followed the instructions and never went low. And no trouble with the medications, numbers stayed in a good range.


@BevJ - All the clear liquid diets I’ve found for diabetics are not sugar free. I guess they are worried about hypos. The prep was 8+oz of Miralax into 1/2 gallon on regular gatorade. That’s about 100 grams of carbs, mostly sugar. I used 50% sugar and no sugar gaterade and bolused for 50g carbs. If I am alive in 5 years I will do something different.