What Does the Spleen Do? A Complete Guide to Your Spleen’s Function, Location, and Common Problems

The spleen is one of those organs most people rarely think about—until something goes wrong or a doctor mentions it after a scan or blood test. You might hear terms like “enlarged spleen,” “splenic rupture,” or “splenectomy,” and suddenly you’re wondering: What does the spleen do, and do I really need it?

Your spleen plays an important supporting role in immunity, blood health, and filtering out old or damaged blood cells. It’s not an organ you can see or feel easily, and it often works quietly in the background—yet it has a big impact on how your body fights infection and manages your blood supply.

Where Is the Spleen Located?

Your spleen sits in the upper left side of your abdomen, tucked under your ribcage, behind your stomach, and near your left kidney. It’s usually about the size of a fist, though size can vary by body type.

Because the spleen is protected by the ribs, you normally can’t feel it. However, if it becomes enlarged, it may extend below the ribcage and sometimes can be felt during a physical exam.

What Does the Spleen Do?

The spleen has three major jobs:

Filters and cleans your blood
Supports your immune system
Stores blood components (a backup supply)

Let’s break these down in plain language.

1) The Spleen Filters Your Blood (Like a Quality-Control Center)

One of the spleen’s main roles is to filter the blood and remove things that don’t belong or don’t work well anymore.

Removes Old Red Blood Cells

Red blood cells (RBCs) carry oxygen. They’re built to last around 120 days, and then they start to wear out. The spleen recognizes old or damaged RBCs and removes them from circulation.

This process also helps your body recycle useful parts of RBCs, such as iron, which can be reused to make new blood cells.

Clears Debris and Abnormal Cells

The spleen helps filter out:

Damaged platelets
Cell fragments
Certain bacteria
Abnormal blood cells (including some that can appear in blood disorders)

In short, it helps keep your blood “clean” and functioning efficiently.

2) The Spleen Supports Your Immune System

Your spleen is a key immune organ. It contains white blood cells that identify and respond to pathogens—especially bacteria in the bloodstream.

Produces and Stores White Blood Cells

The spleen houses immune cells such as lymphocytes and macrophages:

Lymphocytes help recognize specific germs and build immune memory.
Macrophages “eat” (engulf) bacteria and debris.

Helps Make Antibodies

The spleen contributes to antibody production, which helps your body recognize germs it has seen before and respond faster the next time.

This is one reason why people without a spleen (or with a poorly functioning spleen) have higher risk for certain serious infections.

3) The Spleen Stores Blood (A Backup System)

The spleen also acts as a reservoir. It can store:

Red blood cells
Platelets

In some situations—like significant blood loss—the spleen can release some of its stored blood components to help your body respond. This “backup supply” isn’t the same as a blood transfusion, but it can be helpful in emergencies.

Vir-U-Sure

Can You Live Without a Spleen?

Yes, you can live without a spleen, and some people have it removed after injury or because of certain medical conditions. However, losing the spleen means your body loses an important part of its immune defense—especially against specific bacteria.

People without a spleen may need:

Certain vaccines (often additional or on a specific schedule)
Faster medical evaluation for fevers
Sometimes preventive antibiotics in particular situations (varies by patient and clinician)

If you ever have your spleen removed or are told it doesn’t function well, your healthcare provider will typically discuss infection prevention strategies.

Common Spleen Problems and What They Mean

1) Enlarged Spleen (Splenomegaly)

An enlarged spleen can happen for many reasons. It’s not a diagnosis by itself—it’s a finding that points to an underlying issue.

Common causes include:

Viral infections (like mononucleosis)
Liver disease (including cirrhosis and portal hypertension)
Blood cancers (like lymphoma or leukemia)
Hemolytic anemia (conditions that break down red blood cells)
Inflammatory or autoimmune diseases

Symptoms of an enlarged spleen can include:

Fullness or pain in the upper left abdomen
Feeling full quickly when eating (the spleen can press on the stomach)
Fatigue (sometimes due to associated anemia)
Easy bleeding or bruising (if platelets are affected)

Sometimes splenomegaly causes no symptoms and is found incidentally on imaging.

2) Spleen Injury or Rupture

Because the spleen is relatively delicate and full of blood, it can be injured by blunt trauma—like a car accident, sports collision, or fall.

Possible signs of spleen injury include:

Pain in the upper left abdomen
Pain in the left shoulder (referred pain, sometimes called Kehr’s sign)
Dizziness, weakness, fainting (possible internal bleeding)
Low blood pressure, rapid heart rate

A ruptured spleen is a medical emergency because it can cause internal bleeding.

3) Hypersplenism (Overactive Spleen)

Sometimes the spleen becomes overactive and removes too many blood cells. This can lead to:

Low platelets (thrombocytopenia)
Low white blood cells (leukopenia)
Low red blood cells (anemia)

Hypersplenism is often related to an underlying cause of splenomegaly, such as liver disease or blood disorders.

4) Asplenia or Poor Spleen Function

Some people are born without a spleen, have it removed, or develop reduced splenic function from certain diseases (for example, some blood disorders). When the spleen doesn’t work properly, the body is less effective at filtering certain bacteria from the blood.

This increases risk for severe infections—rare, but serious—so prevention and early treatment become very important.

How Doctors Evaluate the Spleen

If a clinician suspects a spleen issue, evaluation may include:

Physical exam (checking for tenderness or an enlarged spleen)
Blood tests (CBC to assess red cells, white cells, platelets)
Ultrasound or CT scan (to assess size, injury, or structural issues)
Additional tests based on suspected causes (infection tests, liver function tests, etc.)

Because the spleen is closely connected to blood and immune function, spleen evaluation often overlaps with hematology (blood specialists), gastroenterology (liver-related causes), and infectious disease.

When to Seek Medical Attention

Seek urgent medical care if you have:

Severe left upper abdominal pain, especially after injury
Dizziness, fainting, or signs of shock
Left shoulder pain after trauma
Fever with a known absence of spleen or poor spleen function

Schedule a medical visit if you have:

Ongoing fullness/pain in the upper left abdomen
Unexplained fatigue or easy bruising
Abnormal blood counts
A known condition associated with spleen enlargement

How to Keep Your Spleen Healthy

There isn’t a specific “spleen cleanse” or supplement that’s proven to optimize spleen health. The best approach is protecting the systems the spleen is tied to:

Prevent infections (good hygiene, vaccines when indicated)
Protect against trauma (seat belts, sports protection)
Support liver health (moderate alcohol, manage metabolic health)
Treat underlying conditions that can affect blood cells or immune function

If you’ve been told you have an enlarged spleen, your clinician may advise avoiding contact sports due to rupture risk.

The Bottom Line

Your spleen is a behind-the-scenes powerhouse that filters your blood, supports your immune system, and helps manage blood components. Most people never notice their spleen—until it enlarges, gets injured, or is affected by another health condition. Understanding what the spleen does can help you make sense of symptoms, test results, and doctor recommendations.