On the left side of the waist are the kidneys of the human body, which are very important organs for excretion, detoxification and circulation. Kidneys are the place where urine is produced, and the glomeruli have to filter the urine twice to expel toxins from the body, which has a very important physiological function. If there is pain in the left side of the waist, it may be triggered by kidney disease, you can go to the hospital to draw blood and test kidney function. If the pain is really triggered by kidney disease, it must be treated as soon as possible without delay, otherwise there will be kidney failure, uremia and other serious consequences. The left side of the waist pain may also be due to lumbar disc herniation, lumbar muscle strain, if such a situation, you can choose conservative methods of treatment, you can generally choose to local massage, hot packs, physiotherapy, traction, the effect is better, can effectively relieve the local pain.