"Insulin spike" is a bit of a misnomer, since it's really your blood sugar that's spiking, because you aren't producing enough insulin to keep up (or are resistant to its effects). Anyway, my understanding is that a healthy, insulin-sensitive person's blood sugar will never go over 120, even after a high-carb binge, and will be back in the normal (70-100) range within two hours. If yours goes over 120, or is still over 100 more than two hours after a meal, there's probably something you could address there.

To add to Aaron's comment about how it's blood sugar that's actually being monitored:

I'd like to add that "Acute insulin spikes" are normal and necessary. In response to sensory stimuli (ie seeing food or smelling food), you secrete insulin to prepare the body for caloric intake.

In response to rising glucose levels (either by carb intake or protein intake thru gluconeogenesis) in the bloodstream, chemoreceptors signal the betacells in the pancreas to secrete insulin.

So, the spike itself is not abnormal, although prolonged and extreme spikes as a result of insulin resistance is indeed abnormal. Your blood sugar doesn't necessarily measure this. It's conceivable that one could have some insulin resistance, take in some glucose, and still have normal blood sugar levels, but only because they body is compensating for the resistance, and doing so by over-secreting and bathing receptor sites with excess insulin.

To test for levels and resistance, you'd want to do draw for insulin levels, c-peptide, insulin tolerance test (ITT), and glucose tolerance test (GTT).

Here is a link that explains things in detail: http://www.phlaunt.com/diabetes/16422495.php

I am a T2 diabetic and anything that spikes me to 120+ and then does not return to my normal level within an hour is a concern, but eating the way I do I do not get spikes anymore and my BG is well within normal ranges.

I'm insulin resistant. A glass of fruit juice sends my glucose levels into a dive...once below 30, which luckily happened in a hospital while getting the hypoglycemia test. My pancreas just doesn't get the ”hey, that's enough insulin” signal. Fructose is by far the worst trigger. Dextrose (glucose) doesn't seem to affect me nearly as bad.

Insulin spikes are needed for the finalization of of your body to produce IGF-1 after a growth hormone spike. Insulin spikes are very anabolic, but the timing of them are critical for protein synthesis and the anabolic process. After a workout is the prime window to have an insulin spike and you don't need fructose or dextrose to accomplish it. Taking Branch Chain Amino Acids will cause an insulin spike just by themselves. Protein with BCAAs and some low GI carbs taken after a workout will maximize the insulin spike to produce IGF-1 and deliver amino acids into the muscle.