Timing of long acting!

I just have a question about this!! My usual long acting dose is 20. I had 10 this morning as I'm going to have 10 tonight as I'm moving it from morning to night. Anyways I ate lunch at 1pm had insulin. Tested at 5pm sugar was 6.5 tested at 6pm sugar was 6.9 tested at 8pm sugar was 7.5. Obviously it was rising very slowly but concidering I only had a half dose of long acting shouldn't it be rising more?