Plasma is a pale yellow fluid that consists of about 92% water and 8% other substances, such as proteins, ions, nutrients, gases, and waste products.

Plasma is a colloidal solution, which is a liquid containing suspended substances that do not settle out of solution. Most of the suspended substances are plasma proteins, which include albumins, globulins, and fibrinogen.

Plasma volume remains relatively constant. Normally, water intake through the digestive tract closely matches water loss through the kidneys, lungs, digestive tract, and skin.