Glucose Response to a 12-Hour Overnight Fast

(Michael - When reality fails to meet expectations, the problem is not reality.) #1


Fasted from 21:00 - 09:00. Went to bed at 22:00 and got up at 08:00. Made several glucose readings during the sleep time at moments when I awoke. The following chart is mmol/L. There’s a conversion chart HERE.


03/06 20:30 - 20:45 Nightcap (creamy bone broth)
03/07 09:00 - 10:00 Keto coffee

PS: for anyone who’s curious, this was totally painless, a very easy peasy way to fast.

[EDIT] I forgot to include my Ketonix BrAce measurement 16.5 ppm at 08:15.

Strange fasting experience
Scared to start fasting - I'm always hungry!
(Michael - When reality fails to meet expectations, the problem is not reality.) #2


Fasted from 20:15 - 09:00 Went to bed at 22:00 and got up at 08:00.


03/08 20:00 - 20:15 Nightcap (creamy bone broth)
03/09 09:00 - 10:00 Keto coffee

(Tracy) #3

I’ve become obsessed over blood sugar lately. Probably because I don’t have anything else to obsess over at the moment. It’s interesting why it even moves while you sleep. I’ve been testing before and after every meal and randomly during the day to see how everything effects me. Keep posting. This is interesting.

(Michael - When reality fails to meet expectations, the problem is not reality.) #4

@kyarn Further adventures with glucose:

(Michael - When reality fails to meet expectations, the problem is not reality.) #5

2020/03/09-10 - 15 hour fast

Fasted from 19:00 - 10:00 Went to bed at 00:30 and got up at 09:30.


03/09 18:00 - 19:00 Secondary meal
03/10 10:15 - 11:30 Keto coffee

(Teb Tengri) #6

Mines usually 50-60 when I wake up and get downstairs to the tester.

You’d think I’d feel horridly hypo at that level but I don’t. I usually wash down coffee with 50-100mL heavy cream, a tbsp of butter and tbsp of coconut oil. Also have about 300mL of water with 2Tbsp vinegar, 10-15g citrulline malate, 2.5g MgβHB, 7-12g KβHB, 1-3g of taurine and 1-2g of β-Alanine.

Hit the gym an hour or so after. I do have little glucose tabs on hand just in case I get that sick, cold sweaty feeling

(Michael - When reality fails to meet expectations, the problem is not reality.) #7

I’m halfway through my FreeStyle sensor, logging every day here.

So far, my biggest surprise is that my glucose is as high as it is, staying mostly in the low-mid normal range. I’ve been keto for 3+ years and in ketosis about 99% of that time. I consume sub-15 grams of carbs per day and frequently sub-10 grams. I am reaching the conclusion that with a normal and healthy metabolism, gluconeogenesis does its job pretty much flawlessly. I have to presume that glucose is getting used for fuel since I’m not gaining weight.

I am also surprised that ketone synthesis continues smoothly even with glucose in its normal range as well. We’ve had discussions here previously wondering whether and at what point glucose interferes with and/or stops ketosis. Whether it’s an on/off switch or a rheostat. In my case, at least, the normal range for glucose seems totally compatible with continuous ketosis.

(Michael - When reality fails to meet expectations, the problem is not reality.) #8

2020/03/10-11 - 12 hour fast

Fasted from 21:00 - 09:00 Went to bed at 00:30 and got up at 08:30.


03/10 20:30 - 20:45 Secondary meal
03/11 09:00 - 10:00 Keto coffee

(Rebecca 🌸 Frankenfluffy) #9

What time do you get out of bed in the morning, Mike? I’d be very interested to know if ‘foot on floor’ syndrome is visible in a non-diabetic?

I take half a unit of insulin around 10 minutes to half an hour (depending on how desperate I am to pee!) before I get out of bed. Otherwise a 4.8 on waking can be 6.8 and rising when I get back from my first brief trip to the bathroom.

I’d be really interested to know what point of your graph is this stage of your day. Your graph in your first post would suggest around 8am, when you went from 3.7 to 4.6. Is that about right?

(Rebecca 🌸 Frankenfluffy) #10

Just reread the whole thread, @amwassil, and your graph from the 9th would suggest that your getting up at 9.30 is visible in the Libre numbers. This is fascinating!

#answeredmyownquestion :flushed:

(Doug) #11

Good stuff, Michael! :sunglasses:

Nice low numbers, Teb. :slightly_smiling_face: There’s a lot of individual variation in where we start feeling faint, etc. I think a lot of people see the ‘normal’ range listed as 80-100, and then “Holy Crow! I’m down substantially from that…”

Once one is fat-adapted, I’ve seen a LOT of cases where they feel fine at 50 (2.8 mmol/L) or even lower. Most of the body runs fine or perhaps even better on ketones than glucose, and so how much sugar do we really need in our blood? It’s only a relatively small portion of our tissues that are needing glucose at that point.

Some individuals on very long fasts have recorded very low numbers while feeling fine and going about their daily activities - lower than I would have previously believed. 40s, 30s, even 20s - in the famous case of Angus Barbieri (382 day fast), he showed up once with a 17 = < 1mmol/L.

(Michael - When reality fails to meet expectations, the problem is not reality.) #12

@KetoSnaps My ‘went to bed’ and ‘got up’ times are listed for each overnight fast. I’ve noticed that my glucose rises even before I get vertical sometimes. I wasn’t doing so originally, but I am now making it a point to take a reading about 5 minutes prior to getting out of bed and 5 minutes after getting vertical. That is about as close together as I can see the two points on the FreeStyle graph.

Please note that I have updated last night’s glucose plot.

(Rebecca 🌸 Frankenfluffy) #13

You’re absolutely right, hence my subsequent post - sorry, I was so busy looking at the graphs to have paid due attention to the words!

Regarding changes in blood glucose, it’s astonishing how little things can make a difference - that ‘foot on floor’ is a killer… (metaphorically speaking).

Also, I need to ‘mop up’ a rise in the early hours of the morning by programming a higher insulin pump basal rate daily from 2am - blood glucose is prone to rise when all those other ‘waking up hormones’ are getting their act together - and as a diabetic I don’t have my own insulin to rely on to counteract that. In your graphs I don’t see any evidence of this ‘dawn phenomenon’ (initially not surprising, in a non diabetic - so it’s interesting that the quote below says that it occurs to some extent in everybody!).

(From Wikipedia)
The dawn phenomenon , sometimes called the dawn effect , is an early-morning (usually between 2 a.m. and 8 a.m.) increase in blood sugar(glucose) which occurs to some extent in all humans, more relevant to people with diabetes.[1] It is different from chronic Somogyi rebound in that dawn phenomenon is not associated with nocturnal hypoglycemia. It is thought to occur due to temporal elevation in serum cortisol, epinephrine and norepinephrine associated with transition from sleeping to wakefulness.

The dawn phenomenon is a normal physiological response and does not require medication adjustment in most diabetics. In most of the cases, there is no need to change insulin dosing of patients who encounter the dawn phenomenon.[2]

Pfffff to the ‘does not require medication adjustment in most diabetics’. My n=1 says otherwise…


(Michael - When reality fails to meet expectations, the problem is not reality.) #14

My glucose ‘bottoms out’ during the 2am - 6am period. It starts to rise again only when I am awake, which depends whether or not I’m working that day and what time I have to start. So I’d say the dawn phenomenon is very individually variant.

(Rebecca 🌸 Frankenfluffy) #15


(Michael - When reality fails to meet expectations, the problem is not reality.) #16

2020/03/11-12 - 15 hour fast

Fasted from 18:00 - 09:00 Went to bed at 00:30 and got up at 08:30.


03/11 17:00 - 18:00 Secondary meal
03/12 09:00 - 10:00 Keto coffee

(Michael - When reality fails to meet expectations, the problem is not reality.) #17

2020/03/12-13 17 hour fast

Fasted from 16:15 - 09:15. Went to bed at 00:15 and got up at 08:00.


03/12 15:45 - 16:15 Secondary meal
03/13 09:15 - 10:15 Keto coffee

This was an interesting experience. My eating was disrupted due to my work schedule (11:30 - 20:00) which did not give me time for a second meal before work and got me home too late for another meal then. So I decided to start the fast as of the end of my meal at work, which I finished about 16:15. You can see from the plot that my glucose rose from 4.6 -> 5.4 after the meal. Then from 17:30 or 18:00 fell slowly at first but steadily until 07:00.

From about 03:00 I was awake as much or more than asleep something noted by @Chantarella here and I commented upon elsewhere here with a link to a relevant article in Scientific American Blog.

By about 06:30 I was fully awake, but still in bed trying to pretend I was sleeping. Glucose was still very low, even though on previous days it had already started to rise by around 06:00 or so. I was curious about my ketones and at 07:00 I got up for about 10 minutes to check. I blew 19.3 ppm on my Ketonix. That’s somewhat above normal for early morning. When I was measuring BrAce daily my morning measurements were generally in the range of 5 - 10 ppm. Seldom above 10. So I presume I was solidly ketogenic all night, which might account for my wakefulness.

As you can see from the plot, when I got up at 07:00 to check BrAce my glucose went up from 3.1 to 3.5, but then went down again to 3.1 by 07:30 before starting to go up again by 08:00. At that point I could not longer pretend I was sleeping to fool gluconeogenesis :confused:, so I got up, and glucose went up with me.

Mike's Excellent Glucose Monitor Adventure
Strange fasting experience
(Michael - When reality fails to meet expectations, the problem is not reality.) #18

2020/03/13-14 15 hour fast

Fasted from 18:30 - 09:30. Went to bed at 01:00 and got up at 09:00.


03/13 18:00 - 18:30 Secondary meal
03/14 09:30 - 10:30 Keto coffee

Note: No problems sleeping last night.

(Bob M) #19

I always got my lowest blood sugar at night. Now, I sleep on my side and the sensor is on one of my arms, but I would change the sensor from arm to arm every 2 weeks.

I also went to bed hours before you did, and got up hours before you are. But all that really does is shift the whole curve to the “left”.

By the way, all you have to do is multiply by 18. So, 3.9 = 70.2.

Unlike you, I always got my highest blood sugar readings in the morning. In addition to the dawn effect, I also exercise in the morning, which leads to higher blood sugar. I also don’t eat in the morning, and usually don’t eat for a while (a few hours) after I exercise. Eating for me causes the start to my dropping blood sugar, although even if I fast, my blood sugar starts dropping around 11 am or so.