How much medicine does it take to hallucinate?

I looked up the ingredients in my cough medicine and i red that the ingredient dextromethorphan can get u high and if u drink a certain amount u will hallucinate...the most ive drank was 12 tsp. but i didnt hallucinate i just felt relaxed and idk y but i was spinning in circles and my speech was different cuz i could barely talk rite...i kno doing that is bad but i dnt care cuz its my life and ive done wayy worse....so how much medicine does it take to hallucinate??