You may have experienced an unexplained bitterness in your mouth before that is not caused by any food you may have taken. This may be a sign that there is excess heat in your body, particularly in the heart or the liver.
Those with excess heat in the heart may have the accompanying symptoms of insomnia, frustration, or have mouth ulcers etc. Those with excess heat in the liver may have other symptoms like short temper, dizziness, headache etc. It is thus important to let your TCM physician know about bitterness or any such unexplained tastes in your mouth as this is important for diagnosis.