ESR (Erythrocyte Sedimentation Rate) Test

Erythrocyte sedimentation rate (ESR), or sed rate, measures how fast red blood cells settle in a tube over one hour. A higher ESR can suggest inflammation somewhere in the body, but it doesn't point to a specific cause, so it's usually interpreted with other tests and symptoms.

Erythrocyte sedimentation rate (ESR) is a blood test that looks at how quickly red blood cells, also called erythrocytes, settle to the bottom of a tall, thin tube over one hour. Red blood cells are made in the bone marrow and normally settle slowly because they repel each other slightly. When inflammation is present, certain proteins made by the liver, such as fibrinogen, can cause red blood cells to clump together and fall faster. ESR does not measure a specific protein or organ; instead, it reflects the overall presence of inflammation in the body. Because many different conditions can raise ESR, the test is considered nonspecific and is usually paired with other markers like CRP for a fuller picture.

Clinicians often order ESR as part of an inflammation panel when someone has symptoms such as unexplained fever, joint pain, muscle aches, or fatigue that might point to an infection or autoimmune condition. It can help support the evaluation of conditions like rheumatoid arthritis, lupus, or temporal arteritis, and is sometimes used to monitor how active a known inflammatory condition is over time. ESR may also be checked alongside white blood cell count, C-reactive protein, and other markers to look for signs of infection or chronic disease. Because ESR alone cannot identify the cause of inflammation, it is typically interpreted together with a person's symptoms, physical exam findings, and other laboratory tests.

Reference ranges for ESR vary by laboratory, testing method, age, and sex, so the numbers on a lab report may look different from another lab's ranges. The table below reflects one commonly used approach; always compare results to the range listed on your own report and discuss any results outside that range with a healthcare provider.

A higher-than-usual ESR can be linked to many different causes and does not point to one specific illness. Common causes include infections of many types, such as bacterial or viral infections, since the body's inflammatory response tends to raise ESR during illness. Autoimmune and inflammatory conditions, including rheumatoid arthritis, lupus, and vasculitis conditions like temporal arteritis, are often associated with elevated ESR. Some blood disorders, including certain anemias and conditions affecting plasma proteins, may also raise ESR. Pregnancy can cause a temporary rise in ESR, as can normal aging, since ESR tends to increase somewhat later in life. Obesity and chronic kidney disease have also been linked to higher ESR values. In some cases, certain cancers, including multiple myeloma and lymphoma, may be associated with a significantly elevated ESR. Because so many different conditions can raise this marker, a high ESR result on its own is not enough to identify a cause. A healthcare provider will typically consider symptoms, other lab results such as CRP and WBC, and imaging before determining next steps.

A lower ESR is less commonly discussed but can also occur for several reasons. Conditions that change the shape or number of red blood cells, such as sickle cell disease or polycythemia, may lower ESR because these cells settle differently than normal red blood cells. Very high white blood cell counts, extreme increases in blood protein levels, or low levels of fibrinogen can also reduce ESR. Heart failure and some liver conditions have been associated with lower ESR readings. Certain medications, including some anti-inflammatory drugs and corticosteroids, may lower ESR as well, since they can reduce inflammation. In most cases, a low ESR is not considered a health concern on its own, but if it occurs alongside unexplained symptoms, a healthcare provider can help determine whether further testing is needed.

ESR is often reviewed alongside other markers to build a fuller picture of inflammation and general health. CRP is another inflammation marker that tends to rise and fall more quickly than ESR, so the two are sometimes ordered together. Hemoglobin and platelet count can help identify anemia or blood disorders that might affect ESR results, while ferritin is sometimes checked when inflammation or iron status is being evaluated. WBC is commonly reviewed together with ESR when infection is suspected. ESR results can vary between laboratories depending on the exact method used, and normal ranges often differ by age and sex. Lifestyle factors such as pregnancy, obesity, and recent illness can also affect results, so context matters when interpreting a single ESR value.

If an ESR result falls outside the expected range, it's a good idea to discuss the finding with a healthcare provider, who can consider symptoms, medical history, and other test results together. Seek urgent care if a high ESR is accompanied by symptoms such as sudden vision changes, severe headache, high fever, or significant unexplained weight loss, since these can sometimes signal conditions that need prompt evaluation. For most people, an isolated ESR result is not an emergency and can be reviewed at a routine follow-up visit. Uploading a lab report to MediWing can help translate ESR and related results into plain language and track how values change over time, which may make conversations with a healthcare provider easier.