Metformin helps to lower blood glucose levels by reducing the amount of glucose produced and released by the liver, and by increasing insulin sensitivity. (Source: Diabetes.co.uk)
I've never seen anything that mentions by how much it can reduce BG levels, can you quote a reference please?
It is rare for someone taking Metformin to have BG going below 4, but you probably shouldn't blame Metformin, even by your calculations that suggest that Metformin lowers BG by up to 1 mmol/mol, without Metformin the BG would be below 5.
By way of a re-cap, I was responding to another poster saying their doctor had said:
"He said that the new guidelines are that as Metformin does not lower your levels you don't need to test, it is only when you go on other medication or insulin."
I wanted to correct that info, because metformin does lower BG levels, as it is intended to. It can cause false hypos, especially in the newly diagnosed (or newly low-carbing), and these can be uncomfortable. Iff the person overcompensates with carbs, their BG increases. I've been having a lot of false hypos lately, so my mind is focused on how horrible I feel when my BG is under 6, and a memory of it being 3.5 after a fast before surgery.
So I said:
"He's incorrect, metformin
does lower BG levels, by up to 1 mmol/mol. In rare cases it can cause the BG to go under 4, which is not very pleasant and can sometimes cause problems."
My source for the first point is (emphasis added):
"
Metformin
Though many people find that they can bring their blood sugar back into the normal range simply by limiting their carbohydrate intake, blood sugar control is not a short term project. When you have abnormal blood sugars you will have to spend the rest of your life keeping them under control, and not everyone is willing or even able to stick with a restrictive diet for the rest of their lives.
For this reason, most doctors assume that dietary changes will not solve their patient's blood sugar problems. So immediately after diagnosing diabetes they prescribe what are known as oral anti-diabetic drugs. Chief among these is metformin.
You may well be asking, if these drugs are effective, why bother with complex and restrictive dietary regimens?
Effective, But Not Effective Enough
Unfortunately, the catch lies in how you define "effective." Just as research has shown that the current criteria for diagnosing diabetes ignore the blood sugar levels at which damage occurs, other research shows that none of these drugs brings blood sugar levels down to anywhere near normal levels. So while an oral anti-diabetic drug might be "effective" by the FDA definition of the term, that effect might only be to lower a diabetic person's fasting blood sugar from a dangerously high 250 mg/dl (13.8 mmol/L) to an only slightly less dangerous 180 mg/dl (10 mmol/L) --a level which is still high enough to encourage the development of serious complications. Even when prescribed for people whose blood sugar is only impaired, as we will see, these drugs
may only lower the OGTT 2-hour reading by 20 or 30 mg/dl (1.1 or 1.7 mmol/L)--which still leaves their blood sugars higher than a damaging 140 mg/dl (7.8 mmol/L) most of the day.
So metformin alone will not be likely to bring your blood sugars back into the normal range."
http://www.phlaunt.com/diabetes/14045911.php
I must have said up to 1 instead of 1.1-1.7 because I was working from memory instead of checking the source. I wasn't far off the ballpark figure.
Now, when it came to writing the second sentence, I made a mistake and forgot about the difference between hypos and false hypos (maybe I was having a false hypo at the time, lol). In any case, this is the part of the above source that I was thinking of:
"Can Metformin Cause Low Blood Sugar?
Metformin is not supposed to cause dangerous hypos. A very few people have found that it causes their blood sugar to drop low enough to make them uncomfortable. This may be because of the phenomenon called
False Hypo. You can read about false hypos
HERE."
Thanks for picking up the mistake in the second sentence.