There are tests you can request of your doctor.

The best is the Kraft test but about no one does them as it takes 5 hours for the full test. A glucose tolerance test is next in line and only takes a couple of hours. If you have had an A1c blood test and it is above about mid 5's it is a good bet you are insulin resistant. If you have had a series of A1c tests and they are creeping up by one or two tenths a year you are likely developing  insulin resistance. If you are above 5.6 pre-diabetic. Above 6.5 diabetic. But really those are just arbitrary distinctions because it is all the same, just on a continuum of not so bad to worse. A C-peptide test is a good proxy for determining insulin resistance but few doctors will order it.

The poor man's way of knowing you are insulin resistant is an expanding belly line. If you have had to buy bigger pants or a larger belt in the last 10 years, you are likely insulin resistant. If you stand naked, look down, and can not see your private parts without bending over you likely are insulin resistant. Again, insulin resistance is not an on or off switch. It is a continuum, from being slightly resistant to full blown diabetic. Also not all parts of the body become resistant at the same time. For example the liver compared to the skeletal muscles.

Any amount of insulin resistance is not good, but the worse it is the worse it is for a persons health.

https://www.youtube.com/results?search_query=dr+ken+berry+insulin+resistance

Hope that helps.

John