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Higher than usual BG after 74-hour fasting?

Discussion in 'Fasting' started by [email protected], Jun 12, 2020.

  1. D@n1el

    [email protected] Prediabetes · Active Member

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    I've just tried for the second time 72-hour fasting. This time it ended up 74-hour. My average BG (7 days) before fasting was 87 mg/dL. During the 74-hour fasting, on the second day, I've got FBG 70mg/dL, but I guess before the dawn phenomenon period (I had insomnia and woke up really early, like 3 am). During the day, it was getting higher and higher until 79 mg/dL (10 pm). The last day, it kept getting higher, and it ended at 85 mg/dL, awesome for my standards. I also measured ketones during fasting: day one 2.7 mmol/L, day two 5.7 mmol/L and day three 7.1 mmol/L.

    This time I was able to break it without problems, I've started with very low quantities and ate more and more on the next meals.

    What seems to be surprising is that the day after fasting my FBG was higher than usual (95 mg/dL), and the next day even higher (98mg/dL). A while ago, 10pm, 7 hours after last meal (I do OMAD), it was 103mg/dL, 1.6 mmol/L ketones. Around 10 pm, 11 pm, I usually get my lowest BG, usually down to 85 mg/dL sometimes (I do suspect that below 2 am is even lower, but I am sleep), but today is really higher.

    I understand that such kind of thing might happen during fasting, but is there a theoretical explanation for it to happen during the days after it?

    I am on low carb diets for about 6 months now. And since a month ago I'm on carnivore, and I just love it. I didn't change my meal quantities either before and after the 74-hour fasting (I kept 2100 calories, <10g carbs, <105g protein and the rest is just fat, sometimes up to 200g).
  2. ziggy_w

    ziggy_w Type 2 · Well-Known Member

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    Hi @[email protected],

    Interesting observation, but also a bit frustrating -- probably.

    My thinking is that what you are observing might be some form of adaptive glucose sparing. Normally, when we are in ketosis for longer period of times, the body realizes that it better save glucose for essential processes (i.e. production of red blood cells) rather than burning it for energy. So, in your case something similar might have happened with fasting. If this is the case, levels might drop back to normal after a while when you again start eating regularly. Just a guess on my part, though.

    But then again, it might also be just be part of normal variations. Personally, I also have some days/short periods when I am slightly higher for no reason and then go through another cycle when blood sugars drop again.
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  3. bulkbiker

    bulkbiker Type 2 · Oracle

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    I have experienced similar patterns after extended fasts . I'm guessing that after a few days of not being required insulin production slows a bit so when you go back to eating anything it takes a while to "wake up" again.

    End of May I had an upset tum and ended up fasting for about 5 days (unplanned) FBG got down to 3.5 mmol/l (63 mg/dl)
    Once I started eating again I had a couple of days of 5.9 and 6 106 and 108.

    Now back to my usual mid 4's to mid 5's.
    It should normalise over time.
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