For a while I would count 30g of carbs for a slice of Dominos pizza because their slices aren't that big. I knew for a fact I was counting those carbs correctly but my blood sugar would still spike even after I gave myself the proper amount of insulin. So, what I started doing when I eat foods that are high in carbs and starch is I add extra insulin or I count carbs higher than they actually are so I get more insulin.
This brings me to the next problem... when you eat pizza, pasta, etc. you are most likely going to use A LOT of insulin. Maybe it's just me. Maybe other diabetics react differently to these foods. I had 2 large slices of pizza for dinner. I counted each slice as 40g of carbs so all together that's 80g of carbs. Now, my carb to insulin ratio is 1 unit of insulin to every 6g of carbs. I ended up giving myself 13 units. That seems like a lot to me.
Now every diabetic is different. One diabetic's blood sugar may not spike as high as mine does when they eat pizza. Some diabetics are on insulin pumps which makes controlling blood sugars easier. But for me pizza does not like me at all! I took a ton of insulin and I'm pretty sure my blood sugar is still going to be high in an hour or so. I can almost bet money on it. The obvious thing to do would be to stop eating pizza. Yeah that makes sense but I'm allowed to cheat every now and then right? :)