16 hour fast RAISING my fasting BG numbers?


I check my blood about twice a week for BG and for ketones. My fasting BG is/was always between 94-98. I started intermittent fasting 5 days ago and since then my morning BG has been high! (108 - 127). Is this normal and something that will come back down once my body adapts?

I have my yearly physical next week and there will be a blood draw before hand - I KNOW I’m going to hear about that number and need some back-up if this is common when starting and that it will come down again.
Thanks in advance.

(Bob M) #2

My blood sugar is always higher in the morning:

Goes down over the day though.

Get your HbA1c checked.


Stop fasting. Are you fasting every day? begin with 2-3x per week.


So it’s not normal to have high BG when starting out fasting? I’m only doing 16-17 hours a day - nothing extreme. I though IF was better if you stayed consistent with it but if I’m doing more harm than good then perhaps I better re-think this.

(Bacon is a many-splendoured thing) #5

Given that there is so much overlap between the error ranges of the glucose readings, I wouldn’t worry too much about them. What were your ketone readings at those same times?

As for the upcoming doctor’s test, presumably he will be ordering more tests than fasting glucose. You have to take the numbers into account as a whole, not focus on just one. For example, your HbA1C and CRP numbers, your liver tests, kidney function tests, are all relevant. Unfortunately, the doctor will refuse to test fasting insulin, because there’s no drug to treat insulin levels.

Dr. Paul Mason, an Australian physician who has gotten into treating patients with metabolic problems, feels strongly that the absolute value of serum glucose is not nearly as important as the range in which it is operating. A higher, but narrower range is much better than wildly fluctuating lower readings, in his view.

One last thought: are you eating enough fat? If not, it is possible your liver is making glucose to meet your body’s energy demands. Once we are keto-adapted, our skeletal muscles actually prefer fatty acids over ketones and glucose, but if there isn’t enough fat to make ketones out of, gluconeogenesis kicks in. Remember that even if we are fat, there is a limit to how much fat our body will allow to be taken from storage in a day.


It is individual. No way in hell I would (or could without great effort and suffering) stop doing IF :smiley: (I actually plan to do OMAD as often as possible but that’s me, that’s more “extreme” and not for everyone, to put it lightly.)
16-17 hour fast is very normal, it gives you a pretty big eating window, even (from my viewpoint, at least. I need bigger, frequent meals in my eating window), I can’t see any problem with it - as long as it suits you, you don’t starve in any meaning of the word (staying hungry or getting too little food). If your body gives good feedback (mine does and it is supposed to be the norm but it can be messed up, maybe someone just doesn’t have a good communication there), listen to your body.

(I can’t help with your original question as I never cared about or knew my BG, my body works and I am happy not to care about it.)

(Bob M) #7

You’re experiencing something many people who eat two meals a day or fewer will experience. It’s not a big deal, but if it freaks you out, just eat in the morning.

But an HbA1c would let you know what’s happening. I had an HbA1c of 5.0 or less WHILE having higher morning blood sugar.


Thank you, that’s reassuring. My blood ketone levels have been running between 0.2 and 0.9, and are almost always low in the morning, higher in the evening.

Really interesting about an no test for fasting insulin, I have always suspected that I am a reactive hypoglycemic - very sensitive and symptomatic when my levels fluctuate. Thanks for the info - very helpful!


Thanks for the thoughts and sharing. I feel great from the time I wake up to the time I break my fast, clear-headed and energetic. It’s when I break the fast that I start running into problems: Nothing seems to fill me, chronic hunger once I start eating, very lethargic, tired and weak. Yesterday two hours after breaking my fast I got very weak and was committed to helping at the animal shelter so I grabbed a protein bar which seemed to help. Perhaps I, too, need to eat a lot more and more often in my window - I was trying to only eat twice a day. That might not be working for me.


Thank you, Bob. I really like the eating window I have set now (about 2:00 p.m. to 9:00 p.m.) so I’d rather not eat in the morning… that period before I break the fast seems to be when I feel my best. I’m not freaked out by the number (much) but I know the doc will be so want to have some info to convince her to let me ride this out before she orders too many tests or meds. You KNOW how they get!


How much do you eat? If you need a big meal, eat a big meal - but I understand if you don’t have an appetite for it, only hunger, I experienced that myself… Whenever I have that, I need bigger variety, more tempting food. But hunger wins anyway, it’s just not as joyous.
Maybe your items aren’t good enough for your number of meals? Not everyone can eat a big meal but a small, dense meal may do the trick…? And of course, certain items just can’t satiate us, no matter their macros. And what food and attitude works with more meals, may not work so well with fewer.

I can relate to feeling fine until breaking your fast… It’s nice to be well-fasted but without hunger yet… I have most energy to do my exercise then. Food can mess up things sometimes, I almost had regrets sometimes when I ate too early, I was already hungry or not so much but welcomed some food but just couldn’t eat a decent meal where I didn’t get hungry too soon. And eating all the time is just annoying. I rather fast more and wait for a proper hunger and time where a more successful meal can be held :wink:


Yup, I need to add some new foods to my arsenal, but I almost think it’s a blood sugar thing: when I used to eat a lot of carbs I was always starving shortly after meals. That never used to happen when I was doin low-carb, but it is these days… not sure why.

My other theory is that this time I’m doing low carb with no dairy… that’s hard! Cheeses and heavy creams are what absolutely satiate me, but without them, I can’t seem to stay satisfied. Peanut butter does the trick, too, but too much of it angers my intestines. If I added dairy back I’d be all set, but then I’d be back to chronically having a clogged up head, ears and nose. :frowning:


Interesting, dairy is not satiating for me and I am not alone, of course it may matter what item we are talking about… (And I am super satiated on high-carb as carbs make me hungry so I tend to overeat. All macros. Getting satiated may be hard but when it arrives, it’s very high level and tend to be long lasting.)

Can’t a significant amount of meat satiate you? Many of us found it’s pretty good for that. At least some kind, not necessarily all kind works for everyone. Eggs are my second best item but nothing compared to meat, preferably not too lean, not too fatty, not fowl. That works like a charm for many of us.


That’s a pretty ignorable rise, you’re not eating, you’re telling your body you’re too stupid to kill something and eat it, that’s a stress to the body, and will show in BG, Cortisol, Adrenaline, Norepinephrine etc.

Almost as quick as you stop fasting for a day or two.