Hi cazab and welcome to the forums. Did they tell you what your HbA1c figure was on diagnosis, please? That might help us to understand where you're starting from. Having said that, if you're getting high readings in and around 20 that's an issue in itself - but it could possibly simply reflect that you had high levels at the point you were diagnosed, and they have not yet started to come down.
Unfortunately fingerprick tests aren't all that useful when "averaged" because it all depends on when you tested. The normal recommendation is to test immediately before eating, and then two hours later.
The aim is for the second reading to be both within 2 points of the initial reading, and not above 7.8. That shows you how well your body handled the carbs in that particular meal. Many people also test "fasted" first thing in the morning - this is often the highest reading of the day.
It might also help us to help you if you could outline exactly what it is you're eating as "very little carbohydrates" could mean different things to different people.
I have zero personal experience with metformin, but it is not usually associated with actively lowering BGs. What it does do is interfere with your liver topping up your blood with additional glucose it's made itself.
Best of luck - this forum is a great resource.
