16.0 is high but not too bad compared with some readings people have, what I would do over the weekend if you have the strips is monitor your BS pre meal and 2 hours after a meal. to see what's going on. Then on Monday ring or see your GP as they may want to change the amount of metformin (only doctors can tell you to change your meds).
If you see very high numbers you may need to seek advice sooner than Monday.
It can also depend if the highs have been going on for a while, as to what action needs taking. Are you eating white bread for instance if so change to wholemeal bread as this will reduce the highs.