The tea made before going to bed at night, get up the next day to drink, the tea has not deteriorated, of course, drinking is no problem. If the tea leaves are soaked for too long, especially at high temperature, they will lose their green color and increase their yellow color. This is the yellow-red and reddish-brown oxidation products formed by the oxidation of tea polyphenols in tea, mainly theaflavins, thearubigins, theabrownins and so on.

This change is day and night. The temperature is higher and changes more during the day. However, if the tea leaves are soaked for too long, it will breed bacteria and deteriorate. Of course not. Generally speaking, it doesn't matter if you drink less than 24 hours.

Tea drinkers should pay attention not to drink a lot of tea when eating. It is okay to drink a small amount of tea before or during meals, but if you drink a lot of tea or drink too much tea, it will affect the absorption of many macro and trace elements.

Pay special attention not to drink tea at the same time when drinking milk or other dairy products. Theophylline and tannic acid in tea will combine with calcium in dairy products to form water-insoluble calcium salts, which will be excreted, greatly reducing the nutritional value of dairy products.

Please refer to People's Daily Online-Can I drink overnight tea?