I vape up to 30ML's or more a day sometimes of 3MG e-liquid and in my opinion you will know when you consumed too much nicotine in too short a period of time because your body is going to tell you. You might get a headache or a stomach ache or some other gastrointestinal symptoms. There are times Sub Ohm vaping with a monster coil will give me a little buzz because I chain vape with a nautilus Mini most often.