Fasting until 2pm. Do I still take my morning Metformin ?

NoMoreBeerAnymore said:

Hi,
I got diagnosed 3 weeks ago with a HBA1c of 120, after my annual health MOT at my GP. My BMI had got up to 35, as I have had to work double shifts the last six months and never had time to either eat properly or exercise. This has stopped because I can't do that anymore. I was breaking out in a Cold sweat every day, usually an hour after eating, and feeling extremely anxious (more than usual) and exhausted, plus I got urinary infection which was truly miserable.

So I am on a low-carb diet (mostly Mosely 800), which I am finding easy to follow. However, I am also Fasting until 2 pm because it is too much hassle to eat in the morning.

I am not having a problem with taking Metformin with coffee before work, and then keeping going until 2 pm. This should keep my circulating levels of Metformin steady, so when I do eat its not going to give me high blood glucose?

I intend to keep this going until I have a BMI of 20, having lost 5 kg already.

Is taking metformin going to stop my weight loss?


Should keep taking my metformin?

Click to expand...

Hi NoMoreBeerAnymore and welcome to the forums.


I have never taken metformin, so can't speak from experience here. However, according to Bilous and Donnilly's Handbook of Diabetes, metformin doesn't itself lower your blood glucose. What it does (and how it does it isn't fully understood) is prevent your liver topping up your blood glucose from time to time from body stores.

Just to point out that we don't do taking/stopping medication advice or diagnoses on this forum. You need to discuss all that with your medical team.

What raises your BG after eating is carbohydrates (all digestable carbs, starches and sugars) being digested to glucose. You don't say whether you're testing your blood glucose levels or not with a glucometer - the NHS won't tell you to do it, although the advice you'll get from me (and from most folks here) is that it's the only way to understand how well your system can handle whatever carbs you're putting in to it.

Tagging @Rachox for the meter list

The method is to take a baseline test just before you eat, and then a second test two hours later. The second test is not to see "how high you go" - your high blood glucose point will almost certainly be reached somewhere in the first 20 to 60 minutes. You're looking for the +2 hr test to be as close as possible to the first - within 2mmol/l of the first, and not above 7.8mmol/l.

What the second test is for is therefore to show how well your system handles that glucose - how quickly it's removed from the blood and transferred to muscle tissue for fuel.

Insulin resistance - which is almost a definition of T2- can mean that muscle tissue won't allow glucose to be placed there. You don't want prolonged high blood glucose levels, and neither do you want the excess glucose being stored as fat. Sio if your system can't deal with the glucose produced, the advice is to limit that food.

This link (written by a forum member) is a good explanation. https://josekalsbeek.blogspot.com/2019/11/the-nutritional-thingy.html

Best of luck. This forum is a great resource. Keep asking questions.

PS - there are decent low carb beers. Example - 1.6g carbs per 440ml

NoMoreBeerAnymore said:

Thanks for taking the time to answer my question!

So if Metformin is not causing me digestive problems, I can just keep going like I am.

My concern is that the Liver will be busy making glucose from fat (I got NASH as well) whilst I am fasting, and will keep the BG high. So keeping the Metformin circulating will allow this BG to get used up rather than making me hyper-thirsty and needing the bathroom.

Click to expand...

I think it's unlikely that your liver will at this stage be using bodyfat to make glucose - because it's unlikely but not impossible that you're in ketosis (ie using bodyfat for fuel). Ketosis both lowers blood glucose (the body only makes what it needs, and it needs only around 130g a day) and uses up bodyfat. I'm in my fifth year of being in ketosis 95% of the time.

If you are, that is (in my view) a good thing as it shows that your carb intake from food is low, and that your body has started to adapt and use up bodyfat. You would be able to test for this either by using a glucometer that also tests for ketones, or by checking for ketones in your urine with "weestix".

Metformin will simply interfere with your liver adding glucose to your bloodstream. You only have about 4g of glucose in your blood at any one time, so you will still need to liver to be doing something - just not dumping massive amounts. Livers are slow learners and will have got used to a higher blood glucose level being "normal" - they will keep trying, but eventually adjust to a new lower "normal". That took me months.