Low carb diet but extra high glucose with carbs

So I’ve been having a really frustrating problem recently and would love to hear if others have had this issue and/or find out why this is happening. I’ve recently started a low-carb diet; one, to try and get rid of a couple of inches around the waist and two, to try and stabilize blood glucose levels. I’m eating roughly 50-60 carbs a day. Well my blood sugar has never been so level. It’s been fantastic. I wear a CGM. Lows and highs drastically reduced. My issue is this: if I stray from that low-carb diet and eat something as mundane as two pieces of bread, my blood sugar skyrockets. I mean skyrockets. More so than when I was not eating a low-carb diet. Even goes higher than you would think would be possible given the number of carbs. And there are no hidden carbs as the food I am eating is known. Today I ate 30 carbs of pita bread at lunch and I’m now up over 249 glucose level. This is after giving my customary insulin/carbs ratio dose. It seems like I need double or triple the insulin now. I don’t understand at all. It’s like I’m suddenly insulin-resistant. But I think that would have been the opposite given that I’m using much less insulin on the low carb diet. And heaven help me if I eat out now. I had a > 425 reading after eating breakfast that included wheat toast and potatoes when away on vacation. And this after giving what used to be an appropriate insulin dose. And a meal I’ve had plenty of times in the past. Anyhow, just really frustrated. I’ve been trying to correct this lunchtime 249 now for a few hours. Three shots now and counting. Glucose not budging.

How active are you?

Sounds like this spike was not just from food, it was from liver glycogen.

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Other people on LCHF diets have also experienced this.

This poster may also be describing something similar to your situation:

I’m not sure what the mechanism is, but it does seem to be a trend for people on LCHF diets.

I’m pretty active. Run 3-4 days a week and lift weights too.

Thanks for the info on the other posts. Yes it does seem to be a trend. And I know I’m burning fat because I have ketones in my urine, but I’ve been told not because of uncontrolled diabetes but because of the low-carb diet … and burning fat for fuel. (?) Well I’m running 5 miles in a bit. Not sure if I should be eating carbs or fat ahead of time!

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If you are running 3-4 times a week with significant intensity, trying to do that on 50-60 grams of carbs per day can be difficult. Do you train with heart rate?

I have a similar reaction now that I eat LCHF; I strayed and ate a small bagel (my weakness when in Montreal). It was one of the highest readings that I ever had and took about 2.5 times my regular bolus. I’ve also found that if I don’t exercise every day; my reaction will be greater when I do succumb to the delights of a warm, sesame seed coated bit of heaven when visiting the Plateau.

@runner1021, I get exactly what you are experiencing. About five years ago I was on a very low carb diet for six months. All was well unless I ate something like 1/2 cup of blueberries. For that 10g of carbohydrate, I’d need to take a whole lot of insulin to keep the lid on. When I finally left very low carb and went to 100-150 grams a day I could cover that berry excursion with a whole lot less insulin. My conclusion - my body, on a very low carb diet, became insulin resistant.


@runner1021 I definitely feel your pain, and @katers87 already linked the thread I started not too long ago that sounds very similar. I believe my issue was a combination of a couple of things-- easing up and eating more carbs (~75-100/day) after a couple of weeks of really low-carb consumption (~20-30/day), as well as the last half of a vial of insulin that may not have been working very well (I’ll go over to the other thread and post some details on this point if you’re interested).

Long story short for me, it all seems like a never-ending series of problems and total inconsistency. I too get really frustrated, but have to stop myself, take a step back, and be thankful for all the tools and information we have that didn’t exist a few decades ago :slight_smile:

I guess for this particular issue, maybe best thing to do is ease back into the carbs after avoiding them for a time.

Good luck!


Yes I seem to be the same as you. I had a low this morning of 64. Ate 1 glucose tablet, just 1, and my blood sugar went to 137. That’s an increase of 73 for 4 carbs! Crazy. Wondering if a moderate carb intake diet may be better for me.

No heart rate. I don’t run particularly fast. Did 5 miles last evening in around 9:30 per mile. Was fine.

Yes sounds similar. I read your thread as well. Good luck to you too! It’s exhausting sometimes.

I cut and pasted the part in quotes from another reply I made below:

“Yes I seem to be the same as you. I had a low this morning of 64. Ate 1 glucose tablet, just 1, and my blood sugar went to 137. That’s an increase of 73 for 4 carbs! Crazy. Wondering if a moderate carb intake diet may be better for me.”

Just wondering if the LCHF is good for me? I mean without the carb splurge, my levels have never been better. I mean I almost eliminated highs and lows. Instead of a roller coaster of glucose levels, it’s a nice flat to small hilly trend. And I feel fantastic. But if I stray and splurge … trouble!

When you don’t eat carbs, you become more sensitive to them. That’s why they say to eat a lot of carbs for 3 days before a glucose tolerance test.

Think of it as having a carb-processing machine in your body. When you don’t eat carbs, the body doesn’t want to waste energy maintaining a machine that isn’t used, so it dectivates the machine, and it takes about 3 days to rebuild the machine if you eat carbs again.

Someone who is starving (the ultimate LC diet) will test diabetic on a glucose tolerance test even if they’re not once refed.

@runner1021 Being in dietary ketosis makes it a whole lot easier to manage diabetes in many ways but, for me, insulin resistance, having to bolus for protein, watching my hair thin, and ketosis breath all took a toll. When I decided to ditch the diet I kept adding carbs by about 25g every week. At 200 a day I started to see resistance again - my I:C ratio was getting pretty narrow. Backed down to 100-150 and I’ve been there ever since. I’m pretty happy with my control and diet at the moment. And my hair is thick again! It’s the little things. :wink:

I have found that for me a moderate carb diet is better. I aim for around 20 carbs a meal, but no more than 30 unless it is a high fiber meal. If I eat less than 20, somewhere comes some extra glucose (liver maybe), but more than 30 a higher bg. I guess that is my limit. For high fiber meals like lentils, I do a dual wave, but other times I do an extended for protein and fat. My control is not as good as some, but isn’t too shabby at 6.1 at last checkup. I am not an athlete by any means, but I am active, I walk, bicycle, or do something everyday. Each one of us is different and I say if you wake up alive and breathing, it is a Hallelujah time.


High Five your 6.1. Mine is the same. I’m happy with that number.

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I’ve read your posts and I know that you know all about running. You know the recommended carb intake for endurance runs. 30-60 grams per hour after the first hour. That’s basically your whole day of carbs right there. There is a reason for those recommendations. It’s the preferred fuel source.

Low intensity runs will also use fat metabolism, but without sufficient carbs, you are robbing your body of another source of fuel.

In your post you said your goal was to lose weight. If you target about a 300-600 calorie deficit every day from your exercise and still keep a reasonable percentage of your calories from carbs in your diet, you will still have sufficient fuel for activity, won’t spike as much with carbs, and can lose about a pound every week.

Yeah I’m bumping up the carbs. Started this morning. Based on my experience of these crazy highs when I do eat a few carbs, I decided I want to just eat a moderate amount daily. Will probably be better all around for my situation.


Another thing to look at is Carbohydrate Periodization. Basically rotating between periods of high and low carb for training. You train with both high and low glycogen stores and the idea behind it is that it helps your body adapt to circumstances of different fuel amounts, and it helps your body build larger stores of muscle glycogen.