What sort of changes? I was under the impression that you know when your blood sugar levels are so high. Did you lose any weight?
But regarding "feeling" when your blood sugar is high, I didn't feel it. However, I had symtoms of always urinating and really thirsty, my friend (diabetic) recognized the signs and tested me. It was 420.
Starting that day, I changed my life, hard.
To this day, I never "feel" my blood sugar fluctuate. I could get it up to 140, and down to 70, and I wouldn't be able to guess. I mean, I could guess by taking into account what I have eaten recently, but never based on "feeling" alone.
Also you could smell your urine, if it stinks like ammonia, your blood sugar levels are high.
If your blood sugar levels are normal you feel healthy.
I've been a T1 since I was 10 and this is my experience. The real problem is not noticing highs but noticing lows. Because low blood sugar is much more threatening than highs for the short term.