I have no idea what sort of diet you have but worth looking at the carb content of your meal. Or another option is an insulin adjustment.
You need to go talk to your Dr and also if you can test every hr on the hr and see what your blood sugar is doing through out the day.
I find that my blood sugar shoots up big time between the hrs of 3 and 4 pm oddly (though it drops down again after with no correction) if I am not careful. This then makes me very tired a few hrs later.