Jackie...
You bought an e-cig that looks like a cigarette, didn't you?
You won't be overdosing, not unless you are using something *insane* like 2-3 cartomiser (cartridge) refills per day.
Do you know E-Lites in the UK? They use 24mg liquid. They claim to do 300 puffs (or something). Whether they do or not is kind of pointless in understanding e-cigs. Each refill (before it runs out) will give the user about half a pack in terms of nicotine (after you've vaped it) regardless if you get 200 puffs or 300 puffs.
This is the big LIE of some e-cigs. The amount of nicotine BEFORE you vape it is NOT the nicotine your body will get.
It is much more responsible for an e-cig company NOT to pretend the product does "x" amount of cigarettes.
I used the 24mg E-Lites. I went from smoking 15 a day to vaping 30 times, 10-15 puffs at a time. I was still getting nicotine withdrawal.
It was also therefore costing me three times as much as roll ups, and I was grumpy, emotional.. constantly in a bad mood.
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We have brands like Nicolites and 10 Motives in the UK. They use 16mg liquid. We pretty much have proved now that ONE refill is approximately 6-7 cigarettes in nicotine.