The number one tell tale sign of high blood sugar, Frequent thirst. This is probably the most noticable of all the symptoms. It is not just a need for an extra glass or two of water, like how you feel on a hot day. This is far more ravenous. Continual need for liquids throughout the entire day and night, an insatiable beast that knows no bounds. This will be extremely appararent if or when the time comes....