What Is Oncotic Pressure and Why Is It Important in Nursing?

SimpleNursing Editorial Team Dec 27, 2023
Young woman female nurse checks the IV line in a hospital room ICU recovery room.

Oncotic pressure might seem like one of those complex terms that’s hard to understand, especially when you’re in the middle of your nursing studies.

But it’s a fundamental concept that underpins many aspects of client care, and understanding it can significantly elevate your nursing practice. Let’s explore what oncotic pressure is, why it’s important, and how you can use your understanding of it to provide better care.

What is oncotic pressure?

Our bodies are expert chemists, constantly balancing different pressures to maintain homeostasis — the state of steady internal conditions.

Oncotic pressure (sometimes referred to as colloid osmotic pressure) plays a vital role in this intricate dance. It counteracts hydrostatic pressure, the force exerted by fluid on the walls of blood vessels.

While hydrostatic pressure pushes water out of the vessels and into the interstitial space between cells, oncotic pressure pulls water back into the bloodstream from surrounding tissues. This delicate balance between the two pressures helps regulate the distribution of fluids in our bodies.

The primary contributor to oncotic pressure is albumin, a protein found in the blood in high concentrations. This protein is too large to pass through the capillary walls, making it an ideal player in maintaining fluid balance.

The role of oncotic pressure in specific body systems

Oncotic pressure plays an important role in many body systems, from the brain to the heart. Here are some specific ways it helps keep our bodies in balance.


Here, oncotic pressure aids in maintaining blood volume and pressure. An imbalance can lead to hypotension (low blood pressure) or hypertension (high blood pressure).


Oncotic pressure influences glomerular filtration in the kidneys. Changes in pressure can affect kidney function, leading to conditions like acute kidney injury.


In cases of hypovolemia (low blood volume), oncotic pressure helps draw fluid back into the blood vessels from the surrounding tissues, helping restore blood volume.

Medical conditions affecting oncotic pressure

Several medical conditions can affect oncotic pressure.

  • Sepsis: This systemic infection increases capillary permeability, allowing proteins to leak out, which increases pressure in the interstitial space and leads to edema.
  • Hypertension: Chronic high blood pressure can damage blood vessels, impacting the balance between hydrostatic and oncotic pressures, which potentially causes fluid accumulation in tissues.

Why is oncotic pressure important in nursing?

Oncotic pressure plays a critical role in maintaining equilibrium within the body.

As a nurse, it’s important to understand how oncotic pressure works and how conditions affecting it can manifest. This will help you assess and monitor clients more effectively.

Knowing when to intervene early and administering fluids or medications if needed helps ensure better client outcomes.

When monitoring a client, you should assess:

  • Serum albumin levels (normal range 3.5-5 g/dL)
  • Signs of edema (non-pitting or pitting)
  • Urine output (oliguria or polyuria)
  • Vital signs (blood pressure, pulse rate)
  • Weight changes (fluid retention or loss)
  • Other laboratory tests (electrolytes, hematocrit)

You can also correct fluid imbalances by administering prescribed:

  • Albumin (to increase oncotic pressure and pull fluid back into blood vessels)
  • Diuretics (to reduce edema and increase urine output)
  • Fluids (oral or intravenous)
  • Other medications, as prescribed by the health care provider (HCP)

Ready to simplify your nursing education journey?

As a nurse, it’s important to understand the intricacies of body functions, like oncotic pressure.

This knowledge helps you comprehend the pathophysiology of various conditions. It also equips you with the ability to provide superior client care.

At SimpleNursing, we believe in breaking down complex medical concepts into easy-to-understand nuggets of information. Our comprehensive e-learning platform will make your nursing education journey a breeze.

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