尿毒症（uremia）是指肾功能衰竭，因而使蛋白质消化后产物、尿素等身体废弃物无法排出，滞留体内所产生的中毒现象。

尿毒症的病因可归类为三方面

Uremia or uraemia (see spelling differences) can be translated as "urea in the blood". Urea is one of the primary components of urine. It can be defined as an excess of amino acid and protein metabolism end products, such as urea and creatinine, in the blood that would be normally excreted in the urine. The Uremic Syndrome can be defined as the terminal clinical manifestation of kidney failure (also called renal failure). It is the signs, symptoms and results from laboratory tests which result from inadequate excretory, regulatory and endocrine function of the kidneys. Both uremia and the uremic syndrome have been used interchangeably to define a very high plasma urea concentration that is the result of renal failure. The latter definition will be used for the rest of the article.