There is 200 mg or more of nicotine in a pack of cigarettes. Research has led to the conclusion that only 10% is actually absorbed, causing the typical pack-a-day smoker to absorb around 20 mg a day. Smoking is acknowledged to be the most effective delivery system for nicotine, even though other products like snus have a higher nicotine content.
Studies of e-cigarette use have found that most of the nicotine in vapor is absorbed in the upper respiratory area (mouth, throat), which makes sense if you consider that most vapers inhale into the mouth before drawing into the lungs. Mouth absorption would be similar to the delivery of gums and lozenges. Either way, it's unlikely that absorption is as high as with smoking, but if it is that would mean we absorb about 10% of what we vape. If you vape 6 ml of 25 mg per day, that would be 15 mg actually absorbed or 15 cigarettes. If you vape 2.5 ml of 11 mg liquid, that would be the same absorbed as approximately 3 cigarettes. If you hold the vapor in and nothing comes out when you exhale, you possibly absorb much more.
However, vapers (like smokers) self-regulate nicotine intake. So, it is unlikely that you are absorbing more than you can handle (you would feel the negative effects if you did) and that you aren't getting any more nicotine than you did when smoking. Your body will tell you "that's enough." In fact, if you were the type of smoker who smoked more for the hand-to-mouth behavior rather than the nicotine, you probably absorb a lot less nicotine than you did when smoking!
