Can You Do A 24h Fast With Type 1 Diabetes?

Recently, I’ve read a lot about fasting, intermittent fasting and how to do it.

Intermittent fasting can be done in many ways, depending on your preferences and lifestyle, and basically means to cut down on calories for a limited period of time, to give the body a chance to use its own reserves.

This can be especially helpful if you’re trying to lose weight, or keep your blood glucose levels more stable. In some cases, these two are interlinked (read: Type 2 Diabetes).

What is important to remember is to still eat enough calories. You just do it within a limited time window. Intermittent fasting makes your body use the energy (food) consumed more efficiently.

And no, skipping a meal (or even two) won’t send your body into a crisis-starvation mode. That takes a good few days to happen.

Intermittent fasting usually has numbers attached to it, depending on how long you’re fasting for;

–       5:2 means you’re restricting calories on 2 days of the week, while eating “normal” the other 5.

–       20:4 means you fast for 20 hours, eating one or more meals within the remaining 4 hours.

–       24/36/48/72:0 simply means a 24/36/48/72 hour fast.

–       16:8 means you eat your meals within an 8 hour time span, fasting the remaining 16 hours.

I’ve done a 16:8 fast in my daily life for a few months now. For me it works really well, as it enables me to keep my blood glucose levels more stable for a longer period of time (which is really beneficial on so many levels!).

And to be honest, in practice it only means skipping breakfast, and eating lunch and dinner as normal. This feels doable for me, and I can easily function without having breakfast every day.

But, is a 24 hour possible to do with insulin dependent Type 1 Diabetes as your BFF?

I decided to test it out, in the name of science. And for this blog post.

For the sake of full disclosure, it didn’t end up being quite a full 24 hour fast, but it was from dinner one day until dinner the following day (which sadly (for science) weren’t eaten at the same time of the day). However, the step from my normal 16 hour fast to 24 wasn’t too crazy in theory.

During that day, I made sure to take extra good care of myself, checking blood glucose levels more often, drinking a lot more water, and taking breaks whenever I felt I needed to. I also took my supplements and medication like I usually do.

You might be thinking that I’m insane, and that’s probably a pretty fair question generally, too. 🙂

Is it possible?

Is it possible?


Well, I’m sure you’re curious now: how did I do?

Let’s do the technical part first.

My blood glucose levels kept stable all day, with a slight downward trend towards the end of the day (before dinner). This is great news for another reason – it means my basal rates are correctly configured! Yay!

My highest reading during the day was 8.0 mmol/l, which was right in the morning, and just might have had something to do with the dinner the night before, being a birthday dinner and all.

My lowest reading was 4.5 mmol/l right before dinner at the end of the fasting day, which is understandable. I don’t know about you, but for me that’s a very successful day in terms of blood glucose readings. (For reference, a healthy person’s blood glucose is around 3.5-8.0 mmol/l in a day, depending on what they eat.)

To keep myself hydrated and help my kidneys filter out some of the toxins that might be lurking in my system, I drank 4 liters of water, 1 herbal tea and 1 decaf coffee (which isn’t even unusual for me, as I cant handle caffeine) throughout the day.

Drinking about 1 liter more water than I usually do per day, naturally made me run to the bathroom more often. Lucky for me that I work from home!

It really felt good to give the body a good rinse through, and I assume that was part of my surge of energy.

Something that I noticed during my fast was that my thinking was a lot clearer. And I was so much more productive!

I felt like I was an idea-shooting-gumball machine. I’m glad I have a system set up for jotting down quick notes, because they were firing from all angles! I’m sure this was a mechanism from my body to keep me busy and not think about food, which was challenging from time to time.

And, I was a little insecure about whether or not I’d have to take many breaks during the day. But in the end, I had to take less breaks than I usually do.

The only breaks I took were for drinking liquids, going to the bathroom and one 30 minute nap in the afternoon (because I had slept so badly the night before).

I also had the feeling that I slept better.

In the night after fasting, I slept better than I have in a long time. And I don’t even have problems sleeping normally. But I felt it was a deeper, dreamless sleep, leaving me more regenerated and rested in the morning.

I only had to get up once to go to the bathroom (damn water!) and took the opportunity to check my blood glucose at the same time. More on that further down in the post.

I also had quite a big realization.I realized just how addicted to food I actually am.

Please note that I’m NOT advocating anorexia nervosa at all, or in any case; that’s a terrible disease and needs to be treated, not to be joked about.

Leaving out the lunch that I usually have at around 12-1pm was actually most annoying and demanding mentally, not physically.

During the day I had a few rumbles in my stomach, and really felt like eating once. But this feeling wasn’t even hunger pains or anything similar – it was mainly my mind telling my stomach that it was time for food (nervus vagus if you want to nerd out about it).

If and when you do decide to do a fast, no matter in which format, remember that a lot of it is in your mind. You have to mentally prepare for not eating. Your body will be fine; in most cases it has more than enough reserves to take from.


I really did feel amazing all day. And I felt fine until the very last hour, which could be entirely psychological.

The last hour I got dizzy, cold, had a few muscle spasms (perhaps I flushed out too much Magnesium with drinking that much water?) and hunger pains. My whole body literally screamed for food!

My very kind and loving husband came home from work and cooked me dinner. Very lucky for me, because I don’t think it would have been a great idea for me to handle sharp objects, such as knives at that point.

For dinner I had zucchini noodles with smoked salmon in a cream sauce, and one piece of leftover low carb, grain-, gluten- and sugar free carrot cake from my husbands birthday the day before. I had to eat like a bird to prevent feeling nauseous, as my stomach was completely empty. This was very difficult – normally I inhale my food (I know, it’s a terrible habit to have!) My total kcal count ended up being 1376 kcal that day. I don’t usually measure, as food should be eaten, not measured, so I don’t really have the value if a normal day.


So, in short, YES, it’s possible and even beneficial in some aspects to fast as a Type 1 diabetic.

For me, dinner was probably the wrong meal to start eating again. I draw this conclusion based on that my blood glucose skyrocketed after finally eating.

It culminated at 14.7 mmol/l at 5am, but came right down after a dose of correction insulin. This could have been a direct cause of fasting, of course. And the only way to eliminate it would be to try a 24 hour fast again. But it could also have been the piece of low carb cake I had (and am not used to having). Or it could have been coincidental. The wonderful part of diabetes, the constant surprise factor! The way I like to look at it is that you at least never have time to get bored!

This is probably nothing I will be able to do on a weekly basis. It might however be a good thing to do every once in a while, if only to keep blood glucose levels that stable.

But trust me when I say that dinner hasn’t tasted that good in a long while that day.

I find this very interesting, and would love to hear your opinion: have you ever done/tried a fast? Tell me your experiences in the comments below!

19 replies
  1. Manfred
    Manfred says:

    Very cool experiment! Im not a diabetic, but am now on my third 6 month-stint of 19/5 fasting. Just wanted to add that physical activity during the fasting phase alleviates much of any (remaining) cravings. Also, the main benefit (although weightloss is a nice sideeffect) certainly is the blood sugar stability. Nowadays I have virtually no swings at all and if I time my excercising properly Im never hungry. Still doing some dairy products but speculating about going full Paleo. Otherwise 19/5 is still viable in a corporate setting (no breakfast, late lunch, early dinner) which is a must for me. Keep trying and thanks for sharing your findings!

    • Hanna Boëthius
      Hanna Boëthius says:

      Thanks Manfred!

      Yes, physical activity is a very useful tool to kill any cravings. In fact, I tried that this morning and it worked like a charm. I also felt unstoppable.

      Good luck on your Paleo journey, and let me know if you need any help!

  2. Max Emanuel
    Max Emanuel says:

    … well done. This is one experiment I didn’t perform yet. The Dr. Mercola Article is nice and easily understandable. Thank you for sharing your experiment.

    • Hanna Boëthius
      Hanna Boëthius says:

      Thanks for your encouraging comment, Max! If this is something you’d like to try, I definitely recommend it. It’s a great experience and gives you more insight. The article from Dr. Mercola is great!

  3. Denise
    Denise says:

    I rarely eat breakfast so I suppose I do minimalist IF on a pretty regular basis. 😉 However, I’ve been considering trying a 24 hour fast.

    I’m a Type 1 with an insulin pump so I might need to lower my basal rate a little but it’s also possible that I won’t need to lower it at all. My last basal rate test was stellar so unless something has changed (and we know that NEVER happens, right?) I should be able to fast without a change in basal rate.

    Thanks for the encouraging entry. If I do this, I’ll come back and let you know how it went.

    • Hanna Boëthius
      Hanna Boëthius says:

      Hey Denise, thanks for your great comment!

      Yeah, I skip breakfasts most days, as it keeps my blood sugar stable for longer. I know EXACTLY what you mean by that things never change with T1D – at least it keeps things interesting, right? 😉 I didn’t have to change anything with my basal rates during my fast, but, as we also know, every one is different. Good luck to you and let me know if you have any questions!

  4. Jessica
    Jessica says:

    Very interesting article. I have been experimenting with 16:8 fasts and I do very well when not eating, but as soon as I eat I sky rocket to 200-300 mg/dl. I have a feeling I may be eating too many carbs (usually about 60 grams).

    • Hanna Boëthius
      Hanna Boëthius says:

      Hey Jessica! Do you eat the 60 g carbs in one meal after breaking the fast? In that case it might be too much for your body to handle at once. I do a 16:8 fast most days myself, but it just helps me keep my blood glucose levels stable for a few more hours before eating. Then again, I barely eat carbs, so that might be why it works so well for me? I shot up to the 200-range when I did the 24 h fast experiment, but that was because I really just ate too much. Hope you find a way that works for you soon!

  5. Jeanne
    Jeanne says:

    Nice write up on IF.
    Am also T1 for over 32 years and started 16:8 a few months ago. It was much easier than I thought, so i tried the 24 hrs fast and really love it. I check my bs regularly to adjust my insulin but IF is defo beneficial for diabetics t1 and t2

    • Hanna Boëthius
      Hanna Boëthius says:

      Hey Jeanne! Awesome, well done! IF with type 1 is no problem at all, as long as you keep a check on your blood sugars and take your basal. It becomes a basal test if nothing else. So happy you’ve dared to go your own way. Thank you so much for reading. 🙂

      • joyce
        joyce says:

        I’d like to join your comments & results on type 1 info, i am newly diagnosed type 1 on insulin now, was type2 for 3 years, don’t know how this happened, I thought i was managing myself better? Sure gave it a heck of a try.

        • Hanna Boëthius
          Hanna Boëthius says:

          Hey Joyce! I’m sorry to hear about your diagnosis, but I promise you it’s not all bad! Could it be that you are actually LADA, which means that type 1 is incredibly slow, yet inevitable, to develop?

  6. Nea
    Nea says:

    Hi and thanks for this great blog! I have couple guestions on my mind i have been trying to find answer to.
    I myself tried this 400kcal/day fasting. Tought it would suit me best, because of my diabetes. And as you did, i was happy to see my glucose staying nice and stabile untill 6pm, before I ate a sallad, my glucose was suddenly 14.2 mmol/l. So I ate my sallad, and took some xtra insulin with my meal. Three hous after, my glucose was 17.
    Friend of my told, that when body feels more hungry than usual, brain sends to liver message: “we need some glucose here, send some!” and so does the liver. Have any ideas if that´s what might be going on?

    And second, I have not found any real information about why everywhere it says that type 1 diabetes and fasting should not be combined? Finnish internet pages offer nothing, found really poorly information about this dilemma in english also.

    Sorry my poor english skils, hope to hear from you :)!

    • Hanna Boëthius
      Hanna Boëthius says:

      Hey Nea! Thanks so much for your comment! First of all, I’m so glad you’re trying things out to find what works for you – that’s brilliant!

      If you ask me, 400 kcal/day isn’t fasting. My theory is then that your body indeed thought there is no more food coming and your liver went to town with extra glucose. Are you eating low carb already? In my experience it’s MUCH easier to combine low carb and fasting than if you’re still eating high carb. The body is used to not using that many carbs for fuel then, and can easier take from your fat reserves.

      Also, I think most medical professionals are reluctant to say anything when it comes to non-traditional ways of helping to treat type 1, as there are many things that can go wrong. Which is why we have to make the effort of finding our own ways even more. 🙂

      Please let me know if you have any other questions! Happy New Year, Nea!

  7. Michael
    Michael says:

    Hi, I have t1 diabetes as well and I am just starting with IF.. Im just on my first week and the feeling is great.. This is a very nice article, I have never thought that a t1 could go on a 24hour fast. I’m mainly doing this for weight loss, i kept reading and hearing from other t1’s that it has that benefit…I hope this works..

    • Hanna Boëthius
      Hanna Boëthius says:

      Hey Michael! That’s awesome, I’m so happy you’re trying new methods to see what fits you! It’s incredible what we can do that we’ve not (well, at least I haven’t) been told. Please let me know if there’s anything I can do to help you further on your journey.


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