In my case I wasn’t measuring for insulin in the blood I was measuring ketones before and after intake of the various proteins. In the case of whey my ketone readings would be around or above 3 mmol/L and after whey it would be <.5 mmol/L which would be indicative of being knocked out of ketosis through an insulin spike.
Walmart blood strip tester?
Which can test blood sugar and ketone levels - I've never heard of strips for insulin levels.