Insulin and Glucose test

My doctor ordered glucose and Insulin test. I have a lot of questions. Are these two separate tests? I am supposed to fast and then do the test? If fasting, for how long? Why does he ask for tests after 30 minutes, 1 hour, 2 hours and 3 hours?

I have been suffering from toe swelling and now knee and hip joint pains.

Thank you.
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