Considering that many e-liquids are based on sweet flavours, this brings on understandable concern for those with diabetes.
E-liquid contains vegetable glycerin (VG), which is metabolizes in the body as a simple sugar. That said, VG in vaporized e-liquid is delivered in small quantities, which normally results in little to no change in blood sugar levels. If you are concerned about vegetable glycerin in e-liquid, you may want to opt for an e-liquid that is higher in propylene glycol (PG) and lower in VG. Similarly, some e-liquids may also include sweetening agents, but these ingredients have not been known to cause significant changes in blood sugar levels.
If you are at all concerned about how e-cigarettes may affect your diabetes, please speak to your doctor.