For me, a spike In a Type 1 is a blood sugar reading above 2.5 mmol/l over the pre meal reading and outside of my personal target BG range at a two hour post prandial test, having calculated the bolus for that meal. Others understanding of what constitutes a spike may well differ
I find that certain foods that are high carb produce an unacceptable spike that is hard to control even if the bolus calculation is correct. . It's a very personal thing, what works out OK for some people , doesn't for another..
Signy