I can not tell you for sure what the reaction will be for you in particular. BUT, I can say that if you doubled the 500 mg fortament, that is 1,000 mg, and about half the maximum does. So any adverse effect would be related to your blood sugar. you need to monitor your blood suger and check it frequently. Contact your doctor for absnormal readings.
the maximum does for Sertraline is 200 mg, so you are at the max.
I would feel better if you call your physician about the Sertraline. I do not know how well you tolerate this drug.
You may see a rapid onset of side effects at the higher dose: Nausea, diarrhea/loose stools, dyspepsia, male sexual dysfunction (primarily ejaculatory delay), insomnia, somnolence, tremor, increased sweating, dry mouth, dizziness.