Blood Sugar and Insulin

If you maintain a fairly consistent blood suger level, does insulin still kick in at some point? Articles I have read talk about “spikes” in blood suger which can cause insulin resistance over a period of time. What is considered a “spike”? I am not diabetic but I bought a glucometer to see how different foods affect my blood suger. Sometimes it stays the same, or goes down, but sometimes it goes up 10 points and sometimes it goes up 30 points. Are these considered “spikes”?