If showing symptoms of lead poisonings (fatigue, insomnia, not thinking clearly, etc), should one be tested? stoneware is commonly used in microwave.

Fatigue & Insomnia: and not thinking clearly indicate a need to see your doc. He/she can test for lead or other toxins if needed. There are many possible reasons for your symptoms. Peace and good health.

Yes: Of course, many medical problems could cause those symptoms, but the cookware, could be a significant issue. If it were me, I would get tested.