The main difference between Dementia and general forgetfulness is that Dementia is a progressive disease that will get worse over time, while general forgetfulness is a temporary condition that many things can cause.
However, some tell-tale signs of Dementia can help determine the requirement of medical advice. These include:
Memory loss that disrupts daily life
Challenges with language (such as speaking, understanding words or sentences, or writing)
Problems with thinking or reasoning (such as math problems)