Overnight mushroom soup can be consumed the next day if it has not been spoiled. If overnight mushroom soup has spoiled, it should not be consumed the next day to avoid gastrointestinal upset or food poisoning. Well-preserved overnight mushroom soup is usually safe to drink if it has not gone bad. However, overnight mushroom soup may be contaminated by pathogenic microorganisms and should not be consumed after spoilage. If the color or smell of the soup changes, it is likely to be due to spoilage, in which case the soup will harbor bacteria and lose its nutritional value, and the taste will also change. If you consume spoiled mushroom soup, you may experience abdominal pain, nausea and vomiting, diarrhea, bloating, and other gastrointestinal discomforts. Severe cases may also show signs of food poisoning such as dizziness, fever, fatigue and headache. It is recommended to eat fresh flat mushroom soup and avoid eating spoiled overnight flat mushroom soup. If abdominal pain, diarrhea and other gastrointestinal discomforts occur after consuming overnight mushroom soup, you need to consult a doctor who will take appropriate measures according to the patient’s condition.