Is it normal to always feeling thirsty despite my glucose level is 4.4 mmol after meal? how can i know if i am not suffering from diabetes insipidus?

Diabetes insipides: You can tell if you have diabetes insipides (di) very easily, without treatment you would be dehydrated. You glucose is normal so diabetes mellitus (dm) is not a reasonable diagnosis. Have a doctor check your blood and urine. If you have a high sodium in the blood and a dilute urine, di is the likely cause. See a doctor to get an answer to your question.