Last year I went for a period of 7 months without getting my period, before that I would get my period twice a month and unusual spotting etc.
I finally went to the gynae and after first doing an ultrasound to see if I had any visible cysts (which there werent) he sent me for an LH blood test and glucose etc, same as yours.
The purpose of this is that they have to assess our hormones, glucose and thyroid tests are done specifically to pick up if you have diabetes or thyroid issues which cause menstrual problems.
Turns out my LH hormone was way too high thats why I hadnt got me period in 7 months! and he put me on the pill after that for a year to regulate it. Now One year later went in for a second blood test and thankfully the LH hormone has stabilised and is normal now.
All these tests are standard procedure so the doctor can diagnose you correctly. Dont stress, I came up negative for I was most worried about and you probably will too. Is best to know if all hormones are normal before its too late so you can get treatment on time. all the best