I Am A 66 Year Old Female Diagnosed With Type

I am a 66 year old female diagnosed with type II Diabetes four years ago. I take Glipizide 5 mg twice a day, and Metforman 1,000 mg twice a day. I am also taking Arimedex, Losartan, and recently stopped Pravachol. Since stopping the Pravachol I have forgotten the last dose of Metforman three times. My blood sugar in the morning is usually in the 150-170 range. When I have forgotten the second dose of Metforman, my blood sugar has been in the 115-125 range. I have not done anything unusual, not dietary or activity. Everything is just as usual except forgetting the pill has resulted in lower morning blood sugar. Why?