| Even if you were a non-diabetic, I wouldn't recommend running a 5K race with no training. If you have been training, then I hope you've been collecting data about what running does to your blood sugars, by testing prior to running and testing afterwards.
That said, and having done 7 5Ks myself, my usual pattern has been that my blood sugar will spike upwards in a 5K, probably from all the adrenaline and the fact that I try to run a 5K near the aerobic/anaerobic threshold which stimulates my body to dump its glycogen reserves. Because of that, I am now usually in the habit of injecting 1 or 2 units of Novolog about 30 minutes prior to a race, depending on what my blood sugar is at that time. I bolded those things I said about myself because we are all individuals and subject to variance in what our bodies will do. You need to figure out what yours will do by testing and observation. | 
