Edema is one of the main signs in patients with kidney disease. In general, patients with kidney disease who develop edema must strictly control water intake to maintain fluid balance. The correct control of water intake is an important part of the treatment of kidney disease. When discussing how to control the amount of water intake, we should first clarify the meaning of “dominant water loss”, “non-dominant water loss” and “endogenous water”. “Apparent water loss” refers to the water lost in urine, feces, vomit, gastrointestinal tract to attract the flow of water. “Non-explicit water loss” refers to water emitted from the skin and respiratory tract. “Endogenous water” refers to the water released from food oxidation and cellular metabolism. The “dominant water loss” is easy to estimate; the “non-dominant water loss” can be calculated by 0.5 ml/kg body weight/hour or 12 ml/kg body weight/day as two practical constants, but of course, appropriate adjustments should be made according to age, body temperature, air temperature, humidity, etc. The calculation of “endogenous water” is more complicated. In practical application, 400-500 ml can be used as a base, plus the previous day’s urine volume, drainage fluid and other discharges. In acute nephritis, nephrotic syndrome and pyelonephritis with significant edema, water intake should be restricted, but in the absence of significant edema, there is no need to restrict water intake. Patients with anuria or severe oliguria generally require only water that is sodium-free and that restores evaporation and small amounts lost in the urine is sufficient. The water intake in the medical prescription should take into account the 350 ml of endogenous water produced daily. In many patients with chronic progressive kidney disease, when oliguria or anuria occurs at the end stage of the disease, they are likely to have had an impaired ability to retain salt and water for several years prior to this condition. Blind restriction of water intake at this time can contribute to further deterioration of already impaired kidney function, and such conditions should be monitored and their loss replaced immediately. Chronic kidney disease patients with heart failure, the excretion of water is reduced, so the amount of water intake should be strictly controlled. In some patients with kidney disease, there are no obvious symptoms of edema, but fear of edema, so blindly restricting water intake is not necessary. When estimating the amount of water intake, we should observe whether the patient has a sense of thirst, eye elasticity, mucous membrane of the mouth and tongue and skin fullness, and also observe the amount of urine, blood pressure changes and colloid osmotic pressure as a reference basis. However, in clinical practice, it is also more convenient and practical to observe the patient’s weight change every day as an estimate of water intake.