There is an association between cardiac function class III feeling nauseous at night while sleeping, but there is also the possibility that it may be caused by poor diet or conditions such as reflux esophagitis or chronic gastritis. Cardiac function class III is a classification of heart failure, suggesting that a slight increase in activity may lead to symptoms of chest tightness and shortness of breath. These patients may also experience nausea and other discomforts while sleeping at night. However, nausea at night is not necessarily caused by tertiary cardiac function. If you do not pay attention to your diet before going to bed and consume too much spicy and stimulating or greasy food, you may experience nausea and vomiting, which can lead to feeling nausea while sleeping. If you suffer from reflux esophagitis, when you sleep, due to the change of body position stomach contents will reflux to the pharynx, which will cause nausea. Chronic gastritis is caused by a variety of causes, commonly Helicobacter pylori infection, patients will experience nausea, loss of appetite, belching (burping) and other symptoms. If you have chronic gastritis, you may experience feeling nausea while sleeping. For patients with cardiac function level 3 who feel nausea while sleeping at night, it is recommended to consult a doctor for examination and clear diagnosis.