In recent years, more and more people advocate drinking milk at night, the reason is that milk contains tryptophan, which helps sleep and can increase nutrition, which is undoubtedly suitable for the general healthy people. But for kidney stone patients, it is different, because people are in the horizontal position during sleep, the urine volume is reduced, the concentration of various tangible substances in the urine increases, and the urine is in a concentrated state at this time. Milk contains more calcium, and most of the kidney stones contain calcium salts. The most dangerous factor for stone formation is the sudden increase of calcium ion concentration in urine in a short period of time. After drinking milk for 2-3 hours, it is the peak of calcium elimination through the kidneys, so when you are sleeping, urine is concentrated, water is reduced, and calcium is discharged more through the kidneys, so it is easy to form stones, therefore, kidney stone patients should not drink milk before going to bed. If you need to drink milk, it is better to drink it 4 hours before going to bed at night.