The proteins as well as sugars in tea belong to the culture medium of bacteria and molds, which can easily lead to the deterioration and corruption of the tea after a long period of time, so it is not recommended to continue drinking it.

If the overnight tea deteriorates after a long period of standing, it will generally lead to a certain degree of oxidation of the substances within the tea, which will not only make the taste worse, but also affect its drinking value, leading to abdominal pain, diarrhea and other symptoms.