Hi Daisy
IIRC there are 2 mechanisms for getting glucose into your bloodstream. The first is by metabolising your food, which you can control by diet.
The second is your liver can decide to dump glucose into your bloodstream if it "thinks" you need a shot, typically early in the morning to get you fired up for the day.
This so- called dawn phenomenon is probably why your morning readings are the highest of the day.
I believe Metformin inhibits this release, thereby allowing you to get the full benefit from your dietary management.
I've been on it since diagnosis last July 92014). Started on 1 per day and increased over a period of weeks to 4.
I graph my results and I felt I could see a step reduction each time the dosage was increased, so I believe it helped me.
Having said that, some 15 months later I feel I have good control and have recently reduced it back to 3, and if things continue to go well I will try for 2.
HTH
Tim