Objective:To investigate the correlation between hyponatremia and the severity of coronavirus disease 2019 (COVID-19).Methods:Clinical data of 12 patients with COVID-19 admitted to Shantou Central Hospital from January 23 to February 5 in 2020 were retrospectively analyzed, including gender, age, symptoms, lab test and clinical outcomes, to analyze the change trend of blood Na + level in the patients with COVID-19. Results:Among the 12 patients with COVID-19, there were 8 males and 4 females with the mean age of (38.0±16.3) years old, most of them were admitted to the hospital with cough and/or fever. All patients had a positive nucleic acid test for 2019 novel coronavirus (2019-nCoV), and were discharged after clinical treatment with oxygen therapy, antiviral, antibacterial, anti-inflammatory, and nutritional support. All patients were of ordinary type when they were admitted to the hospital. Among them, 1 patient turned into a severe case during the course of the disease, and 1 patient showed a tendency to become severe case. It was found that 10 patients without severe conversion had an average blood Na + of (138.3±1.3) mmol/L at admission, and the lowest blood Na + during the course of disease was (135.9±3.1) mmol/L. However, 2 patients who became severe and had a tendency to become severe disease (Na + levels at admission were 140.0 mmol/L and 138.0 mmol/L, respectively) experienced hyponatremia during the course of the disease (the lowest blood Na + levels were 129.0 mmol/L and 122.0 mmol/L). Further analysis showed that the lower serum Na + level, the higher level of white blood cell count (WBC) and C-reactive protein (CRP), but serum Na + level was consistent with the change trend of lymphocytes, suggesting that hyponatremia was closely correlated with severe inflammation reaction. Conclusions:Serum Na + showed decreasing tendency during the development of COVID-19, and hyponatremia was closely related to the severity of COVID-19. It was necessary to pay great attention to the change trend of blood Na + level. However, further research was needed to obtain more reliable conclusions and explorer the pathophysiological mechanisms.