What is the primary function of albumin in the blood?

Albumin plays a crucial role in maintaining osmotic pressure in the blood, which is essential for proper fluid balance within the body. As the most abundant plasma protein, albumin acts primarily by attracting water to the vascular space, thus preventing excessive fluid from leaking out into the surrounding tissues. This is vital for various physiological processes, including the regulation of blood volume and pressure.

When the concentration of albumin is adequate, it helps to keep the capillaries from becoming overly permeable, which can lead to edema (swelling) in tissues. An insufficient level of albumin can result in decreased oncotic pressure, causing fluid to accumulate outside of the blood vessels, which potentially leads to conditions like ascites or generalized edema.

While albumin does have secondary roles, such as the transport of various substances—including some hormones and fatty acids—its primary and most significant function is the regulation of osmotic pressure in the circulatory system, ensuring that the right amount of fluid stays in the vascular space.