Drinking black tea in moderation over a long period of time is generally not harmful, but long-term overdrinking of black tea may cause stomach discomfort, poor sleep quality, constipation and other hazards. 1. Stomach discomfort: long-term excessive drinking of black tea will affect the secretion of gastric juice, causing gastrointestinal discomfort, stomach bloating, stomach acid, nausea, vomiting and other symptoms. 2. Poor sleep quality: black tea contains caffeine, theophylline, etc., which can stimulate and excite the nervous system and refresh the mind. If you drink black tea in excess for a long time, you may have poor sleep. 3. Constipation: black tea tannins and proteins generate ellagitannins, if you drink a lot of black tea for a long time, it may cause the gastrointestinal tract peristalsis function to weaken, resulting in the occurrence of constipation. It is recommended to drink black tea in moderation to avoid discomfort.