What Causes Sudden Spike In Blood Sugar Level?

I have type 2 diabetic, I didn t measure my blood sugar for 3 weeks, I measure it two days ago it was 11.8 three hours after lunch. today I had my lunch at 2:30 p.m, and I measured my blood sugar at 7:30 p.m it was 11.5. is that normal? I take two 500mg metformin after breakfast and supper. was the 11.5 spike normal? thank you