It happened to me earlier in the year, BS climbed rapidly into the 20's, can be down to a number of things. Have you changed your eating habits / foods you eat, gained weight, I had lost a bit of weight or its just a progression of the diabetes which in the end it is for me.
I have relooked at what I was eating and restarted getting things back under control, have also been an various doses of gliclazide now on 120 mg. My BS is currently swinging high and low and need to sort that bit out.