Saline is an isotonic solution, drinking large amounts of saline for a short period of time can cause an increase in blood volume. Drinking large quantities of saline within a short period of time, the liquid into the blood circulation leads to blood dilution, a short period of time will cause an increase in blood volume, the increase in sodium in the body will cause a rise in blood pressure, there can be a short period of time dizziness and other phenomena. However, the human body has a regulatory mechanism, when a large number of drinking saline blood volume increase, caused by increased heart rate, increased cardiac output, increased renal blood flow, so that the glomerular filtration rate increased, increased urine, excessive intake of water and sodium is excreted through the urine. With the excretion of urine, the blood volume in the body also returns to normal. However, drinking large amounts of saline for a long time is not good for the body, can cause sodium accumulation, blood pressure increases. If you have cardiac and renal insufficiency and other diseases, it will lead to sodium and water retention, causing aggravation of the condition. If necessary, follow the doctor’s instructions to use saline, do not blindly drink saline.