Urea nitrogen 2.2mmol/L belongs to the mildly low, generally speaking, there is no great harm, the main clinical attention to find the reason for the decrease in urea nitrogen, and give the corresponding corresponding treatment can be. The normal reference range of urea nitrogen is between 3.2~7.1mmol/L, which is mainly used to reflect the renal function. Generally, its decrease can indicate nutritional deficiency, but usually there is no special harm, it is recommended to supplement nutrition and continue to observe. Clinical urea nitrogen reduction can be seen in malnutrition patients, or long-term vegetarian diet, and meat, eggs and dairy consumption is relatively small crowd, this kind of people in the adequate supplementation of nutrition, urea nitrogen value can be returned to normal, do not need to worry too much. However, it is worth noting that once the urea value changes significantly beyond the normal range, it is necessary to be alert to the presence of disease. In summary, urea nitrogen 2.2mmol / L has a slightly low, but generally does not have a great harm, if you have uncomfortable symptoms, need to consult a doctor in time.