If you take pain medication on an empty stomach, it can lead to the following adverse effects: 1. stomach discomfort, such as bloating, stomach pain, indigestion or loss of appetite, and in serious cases, it can induce gastric ulcers, bleeding and perforation of gastric ulcers. 2. liver damage, such as elevated transaminases, large liver, liver discomfort and other symptoms. 3. kidney damage, such as kidney insufficiency. 4. 4. symptoms of allergy, such as skin rash, drug fever and erythema.