First off buy a $50.00 blood sugar monitor. Secondly, buy some gluecose tabs. Check you bloodsugar before you inject. Make sure you BS is around 90-110 before you start. I would only recommend 2-5 units of insulin, and 5 is a shit load for your body to handle. It will honestly drop your BS to 20 in 15 mins.
MAKE SURE YOU TAKE SUGAR WITH INSULIN. And not just any sugar, you need simple sugar, glucose, dexitrose, shit like that. Keep checking your BS every 10 mins or so for the next 45 mins. And if you keep dropping dude...keep pumping the sugar.
Good luck to you, researsh, done run insulin too long and you will be fine.