After taking long term insulin why did my bs drop 50 points in 5 minutes?

Can recheck: If one is using Insulin and notices a sudden change in the blood glucose reading, she can double check the Insulin to make sure the dose is correct, and then retest the blood sugar. Sometimes, a blood sugar result is not correct, due to reasons such as machine error, problems with the test strip, human error, etc... The doctor can evaluate if there are worrisome concerns.