Undernutrition can result from inadequate intake; malabsorption; abnormal systemic loss of nutrients due to diarrhea, hemorrhage, renal failure, or excessive sweating; infection; or addiction to drugs.

• 营养低下可由摄入不足、吸收不良、腹泻、出血、肾衰或过度出汗而至营养素丢失、感染和吸毒等引起。