Test library
Erythrocyte Sedimentation Rate Test
An ESR test measures how quickly red blood cells settle in a sample tube, a general marker of inflammation. It is often ordered alongside other tests to support an evaluation.
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Order ESR Test- Typical turnaround
- 1-3 business days
- Starting price
- From $49
- Results
- Confidential, online
Quick answer
An erythrocyte sedimentation rate test, commonly called ESR or sed rate, measures how quickly red blood cells settle to the bottom of a tall, thin tube over a set period. A faster settle can be associated with inflammation somewhere in the body. It is a general marker rather than a specific diagnosis, so results are interpreted with other tests and a provider evaluation.
What this test measures
The ESR test works by measuring the distance red blood cells fall in one hour. Inflammation can cause red cells to clump and settle faster than usual. Many conditions can raise the value, including infections, autoimmune conditions, and some cancers, and the result can also be influenced by age, sex, pregnancy, and anemia. A normal result does not rule out disease.
A blood sample is collected from a vein, usually into a tube containing an anticoagulant. The laboratory reports the result in millimeters per hour and compares it with a reference range that varies with age and sex. ESR is frequently ordered together with C-reactive protein, which is a different marker of inflammation.
People may order this test when a provider is evaluating joint pain, unexplained fever, or other symptoms that could involve inflammation, or when monitoring a known condition over time. Because it is non-specific, ESR is rarely interpreted alone. A qualified healthcare provider should explain what the value suggests in the context of your health.
- Erythrocyte sedimentation rate (mm/hour)
- C-reactive protein (when included)
- Hemoglobin
- White blood cell count
- Platelet count
- Rheumatoid factor (when included)
- Antinuclear antibody (when included)
Why people order this test
- Evaluate suspected inflammation
- Investigate joint pain or stiffness
- Review unexplained fever with a provider
- Monitor a known inflammatory condition
- Part of a broader blood panel
- Establish a baseline before a provider visit
How to prepare
No fasting is usually required for an ESR test, though it may be requested if other components of the panel require it. A blood sample is collected from a vein. Mention any medications or health conditions as directed by the laboratory.
Understanding your results
Results are generally available within 1-2 business days. The value is compared with a reference range that varies by age and sex. An elevated result suggests possible inflammation but does not identify a cause, so a qualified healthcare provider should interpret it with other findings and your history.
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Frequently Asked Questions
What does the ESR test measure?
It measures how quickly red blood cells settle in a tube over one hour. A faster rate can be associated with inflammation somewhere in the body.
How is ESR different from CRP?
Both are general markers of inflammation. CRP reflects a different protein response and may rise and fall on a different timeline, so providers sometimes order both.
What can raise an ESR?
Infections, autoimmune conditions, some cancers, pregnancy, and anemia can all influence the result, which is why it is interpreted with other findings.
Can ESR be normal even when a condition is present?
Yes. A normal result does not rule out disease, and a provider may order additional tests based on your symptoms.
Do I need to fast?
Fasting is not usually required for ESR alone, but it may be requested if glucose or other panel components require it.
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