I’ve been taking 500 mg/day since 14 April and been testing my bs since March 2020 on an ad hoc basis The past couple of weeks I’ve been testing my bs before and after meals etc and I can’t see any change ( except lots of holes in my fingers!). It’s still the same as it was before starting the Metformin. I have been eating a low carb diet since March 2020. My GP told me my diabetes is either genetic or age- related ( I’m 75) I have no symptoms apart from the hba1c test (67) in April. My fasting bs is between 8 and 10 and during the day it goes up and down but by the end of the day it’s pretty similar to the fasting result regardless of how far I’ve cycled or what I’ve eaten. Advice please!
The standard dose of Metformin is usually up to around 2g (that is 4 x 500mg tablets). Doctors often prescribe it one tablet to start, building to the higher dose if it is tolerated. Other tablet sizes are available, including slow release versions. which carry different dosage guidance.
You are just on one tablet, so it is only to be expected that the benefit you will see will be smaller than if you were on a bigger dose.
Having said that, Metformin has been researched in a number of studies. This is a link to a meta study on the drug (it is an old study, but then Metformin has been around since at least the 60s)
https://pubmed.ncbi.nlm.nih.gov/18261504/
And here is a link to an interesting study showing that Metformin, on average, depending on optimum dose, lowers the HbA1c by approx 1.1% (American units) which equates to lowering the UK measurement of HbA1c by approx 11mmol/mol. As an example, that would reduce it from 53 to 42 mmol/mol.
https://care.diabetesjournals.org/content/diacare/35/2/446.full.pdf (Feb 2012)
With evidence like this, from multiple studies, I can never understand why people dismiss Metformin as ineffective and not lowering blood glucose.
I do agree that this reduction would be much harder to see on a daily or meal by meal basis, but it is still a significant reduction, especially when compared with other T2 glucose lowering oral medications.
Consequently, Metformin certainly does have an effect on blood glucose levels (depending on dose and other factors such as average blood glucose levels), but changes in those levels will also depend on what other measures are being taken to control blood glucose:
https://www.diabetes.co.uk/insulin/diabetes-and-metformin.html
Regarding your porridge - it doesn't really matter if the carbs are labelled fast or slow, or whether it fills you up until lunch. The real question is what it does to your blood glucose, and how well your body tolerates the portion size you have.
Edited for clarity