How Low is Too Low on Extended Fast?

[droog]

I am a 55 yo male, type 2 (diag 2012) on Metformin only (2000mg extended release). Last two A1C: 30.1 mmol/mol (4.9%). Current weight 210 down from 400+ a few years ago. No complications. Diet: VLCHF, < 20gr carb daily. Well most days.

Fasting Regime: Water, tea, black coffee, vitamins & salts only.

After 3-4 days of continuous fasting, I am in deep purple ketosis and my blood sugar typically hovers around 3.6 mmol/l (65 mg/dl). But occasionally has dipped down around 3.0 mmol/l (55 mg/dl), confirmed by two tests 10 minutes apart. When it is in the 50's I definitely feel low energy. Having blood sugar in the 50's concerns me and I break my fast.

However, I have read that some experiments from decades ago demonstrated that fasting patients in ketosis showed no ill effects from blood sugars below 20 following injection of insulin. While I am understandably skeptical about that...

QUESTION: How low is too low when on an extended fast?

Thank you.

Oh, anyone have a reference to the study I mentioned, I can't find it?

 

[bulkbiker]

I've experienced 3's usually on day 3 of a fast but it soon goes back up to the low 4's for days 4-7 (never gone for more than 7 days)
The study you are looking for is I believe one of George Cahills of the 1970's where they injected people in deep ketosis with insulin to drive their BS levels down to the 2's with apparently no ill effects.

I'll see if I have a link to it.

Edit to add I think its this one but I haven' t read through it to check! Sorry cooking dinner

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2441301/pdf/tacca00109-0225.pdf

 

[droog]

Bulkbiker,
Thank you for your reply. I read through the document you posted. It didn't mention the experiment regarding inducing extremely low blood sugar during deep ketosis, but it was fascinating reading none the less.
All the best,
Droog

 

[LaoDan]

Great work on the weight loss!!!

 

[MarkMunday]

... QUESTION: How low is too low when on an extended fast? ...

Low blood glucose is a concern if there is excess insulin action driving it down. As you are not using insulin, IMO low blood glucose should only be a concern if you are not feeling well. The liver will supply enough glucose to keep you going until you end the fast..

 

[bulkbiker]

Bulkbiker,
Thank you for your reply. I read through the document you posted. It didn't mention the experiment regarding inducing extremely low blood sugar during deep ketosis, but it was fascinating reading none the less.
All the best,
Droog

Sorry about that I'll have another dig around. It was mentioned in a Phinney video and I'm sure I have a link saved somewhere...

 

[bulkbiker]

Bulkbiker,
Thank you for your reply. I read through the document you posted. It didn't mention the experiment regarding inducing extremely low blood sugar during deep ketosis, but it was fascinating reading none the less.
All the best,
Droog

I think this is the one..

https://coconutketones.com/wp-content/uploads/2016/10/CahillGF_CerebMetabolism.pdf

 

[droog]

Well... I hit a new low today. On the third day of my fast I hit BG=45 (2.5) and confirmed it a few minutes later as BG=46.

This was around 12:30 pm. I felt fine. No problems what so ever. An hour later it was up to 55 (3.0). Three hours later it was 65 (3.6). By then I was feeling tired. Time for a siesta.

 

[droog]

Anyone else letting their blood sugar crater during extended fasts?

 

[Roggg]

Mine doesn't crater. I've never been into the 3s, even on multi-day fasts. TBH I would probably be a little bit freaked out if it did.

 

[LaoDan]

Checking my history, lowest I’ve been is 3.6. note, I’m not using insulin.

I usually feel ok at this range if I’m in ketosis, otherwise I feel like I’m out of gas.

 

[bulkbiker]

Anyone else letting their blood sugar crater during extended fasts?

You still taking the metformin?
Might be worth considering dropping it if extended fasting?
See what happens then?

 

[brassyblonde900]

Well... I hit a new low today. On the third day of my fast I hit BG=45 (2.5) and confirmed it a few minutes later as BG=46.

This was around 12:30 pm. I felt fine. No problems what so ever. An hour later it was up to 55 (3.0). Three hours later it was 65 (3.6). By then I was feeling tired. Time for a siesta.

I find that with any Abbot freestyle glucometer, my BG give ultra low readings on fasts.
I have driven myself crazy testing with multiple glucometers.
I now use a CGM and just watch trends which for better or worse lets me know how meals impact me.