3. Headache, Nausea, Shakiness - but see #V4
These, together with irritability, inability to concentrate, poor sleep, depression and so on, are common nicotine withdrawal symptoms. If you are using a low-strength refill liquid and not absorbing as much nicotine as when you normally smoked, you can experience these withdrawal symptoms, which typically last only a few days to a week. Perhaps the use of a higher nic strength refill liquid might be a good idea temporarily, reducing the strength as needed.
V4. Headache, racing pulse, dizziness, slurred speech, inability to sleep
These are nicotine overdose symptoms. Sometimes we overestimate just how much nicotine we were getting with regular cigarettes, and underestimate how much we are vaping, particularly at the beginning. Racing pulse is the most common, slurred speech less so. Headache can be severe. Try cutting down the nic dosage in your cartridges or liquids or vaping less frequently. The nicotine strength can be easily reduced by adding some VG (Glycerine, USP - obtained from a pharmacy), although this will also reduce the flavor.
It is said that some people experience this even with a low nicotine liquid and find that switching to VG solves their problems, although such a symptom of PG intolerance is not widely believed to exist never mind be proven. It is far more likely that such a reduction of the symptom/s would be due to an intolerance to flavorings, colorings or similar used in an eliquid, and changing to a VG liquid simply removed those particular ingredients - see footnote.
http://www.e-cigarette-forum.com/fo...hen-quitting-tobacco-changing-ecigarette.html
