ESR Test – Erythrocyte Sedimentation Rate

The erythrocyte sedimentation rate (ESR) test measures how quickly red blood cells settle at the bottom of a tube over one hour and serves as a simple, widely used marker of inflammation in the body. Clinicians order ESR to help detect, monitor, and gauge the severity of inflammatory conditions—such as infections, autoimmune diseases, and certain cancers—or to track response to treatment, though it is non-specific and often interpreted alongside other tests and clinical findings. Normal ESR values vary by age and sex, so results must be assessed in context; elevated or abnormal readings prompt further evaluation to identify the underlying cause.

ESR Level Interpretation & Clinical Use

ESR results are typically reported as millimeters per hour and interpreted relative to age- and sex-specific reference ranges: modest elevations may reflect chronic or low-grade inflammation, while markedly high values suggest acute or systemic inflammatory processes such as severe infection, active autoimmune disease, or malignancy. Because ESR is non-specific and can be affected by anemia, pregnancy, and medications, clinicians use it alongside CRP, clinical assessment, and imaging; trends over time (rising or falling ESR) are often more informative than a single value for monitoring disease activity or response to therapy.

What is ESR and How is it Measured?

The erythrocyte sedimentation rate (ESR) is a simple blood test, usually performed by the Westergren method, that measures how far red blood cells fall in a vertical tube over one hour and is reported in millimeters per hour; it serves as a non-specific marker of inflammation used to detect, monitor, and gauge the severity of conditions such as infections, autoimmune diseases, and some malignancies. Because normal ESR varies with age and sex and can be influenced by factors like anemia, pregnancy, and certain medications, results must be interpreted in context and typically alongside CRP, clinical findings, and imaging; modest elevations can reflect chronic or low-grade inflammation while very high values point to acute or systemic inflammatory processes, and serial measurements (trends) are often more clinically useful than a single value.

Normal ESR Values & Age/Sex Variations

Normal ESR values are reported in mm/hr and vary by age and sex: a common rule of thumb is an upper limit of roughly age/2 for men and (age+10)/2 for women (e.g., ~20 mm/hr for a 40‑year‑old man, ~25 mm/hr for a 40‑year‑old woman), with younger adults typically having lower values and older adults higher; values can also be elevated by pregnancy, anemia, and certain medications, so results must be interpreted with clinical context and often alongside CRP or serial measurements.

Elevated ESR: Causes & Interpretation

An elevated ESR indicates increased inflammation but is non‑specific: common causes include infection (especially severe or systemic), active autoimmune or inflammatory diseases (e.g., rheumatoid arthritis, temporal arteritis), malignancies, and chronic inflammatory states; physiologic and noninflammatory factors such as pregnancy, anemia, advancing age, and certain medications can also raise ESR. Interpretation requires age‑ and sex‑adjusted reference ranges, correlation with symptoms, CRP and other labs or imaging, and often serial measurements—modest elevations suggest chronic or low‑grade inflammation, while very high values point toward acute or widespread inflammatory processes needing prompt evaluation.

Low/Normal ESR & Clinical Significance

A low or normal ESR generally suggests absence of a significant systemic inflammatory response and, when concordant with a normal CRP and unremarkable exam, lowers the likelihood of active infection, widespread autoimmune inflammation, or malignancy; however, a normal ESR does not exclude localized infections, early or purely cellular immune responses, neutropenia, or conditions that do not raise fibrinogen, and values can be artificially low in polycythemia or hypofibrinogenemia. Clinical context, other labs (especially CRP), and imaging or repeat testing when symptoms persist are essential for appropriate interpretation.

How to interpret your results

Your ESR result comes back as a single number in millimeters per hour (mm/hr) — the distance your red blood cells fell in a vertical tube during one hour of settling. The number itself only tells you how much your red cells are clumping; it does not name a specific disease. Interpretation depends on your age, sex, current symptoms, and other lab results, especially CRP (C-reactive protein), which is often run alongside ESR.

Reference ranges from the standard Westergren method:

Population	Upper limit (mm/hr)
Men under 50	15
Women under 50	20
Men 50 and older	20
Women 50 and older	30
Children	10

A value above your age- and sex-specific cutoff is generally read as evidence of inflammation somewhere in the body, but the size of the elevation matters. Mild-to-moderate elevations without an obvious cause may simply reflect pregnancy, menstruation, advancing age, or normal lab variability — they are not automatic cause for alarm.

What “mild,” “moderate,” and “marked” elevation usually mean

A useful framing is to think of the result in tiers, even though no formal cutoffs exist:

Mild elevation (a few mm/hr above your cutoff): often nonspecific. Pregnancy, menstruation, anemia, obesity, regular alcohol use, advancing age, and certain medications can all shift the value.
Moderate elevation (clearly above the reference range, but well under 100 mm/hr): commonly seen in chronic infection, autoimmune disease, inflammatory bowel disease, or low-grade inflammation. Your clinician will weigh symptoms and order other tests rather than treat the number itself.
Marked elevation (above 100 mm/hr): strongly associated with serious underlying disease. Infection accounts for most cases of extreme elevation, followed by collagen vascular disease and metastatic cancer. An ESR over 100 mm/hr has a low false-positive rate — meaning a pathologic cause is usually found.

A single ESR is a snapshot. Trends matter more than any one value: a falling ESR during treatment for a known inflammatory condition can suggest improvement, while a rising or persistently high value may justify further workup. Repeat testing after several months is a reasonable approach for asymptomatic people with a persistently elevated result. For complementary inflammation testing, your clinician may pair ESR with CRP, hs-CRP, or a complete blood count to build a fuller picture.

ESR vs CRP: when each test is more useful

ESR and CRP are both general markers of inflammation and are frequently ordered together — MedlinePlus notes that “a CRP test is commonly done with an ESR to provide more information”. The two tests measure different things and respond on different timescales, so they often complement each other rather than substitute for one another.

ESR is an indirect measure: it reflects how much red blood cells clump (form rouleaux) in the presence of plasma proteins like fibrinogen and immunoglobulins. CRP is a direct measurement of one specific acute-phase protein produced by the liver in response to inflammation.

Feature	ESR	CRP
What it measures	Rate of red blood cell settling, influenced by fibrinogen and globulins	Concentration of C-reactive protein, an acute-phase protein
Influenced by red cell count or shape	Yes — anemia, polycythemia, sickle cell can skew result	No
Useful for tracking trends	Yes, including monthly intervals	Yes, including short-term changes
Often ordered together?	Yes — commonly paired for added information	Yes — commonly paired for added information

When clinicians lean on each

ESR is particularly useful when monitoring chronic inflammatory conditions where doctors want a stable, slow-moving marker — for example, in polymyalgia rheumatica and giant cell arteritis. CRP is more responsive to short-term changes in inflammatory activity and is less affected by red blood cell abnormalities.

Neither test is a perfect screening tool. Both ESR and CRP can be normal in people with active rheumatoid arthritis, lupus, or osteoarthritis, and both are poorly correlated with day-to-day clinical disease activity in those conditions. Using them together — alongside symptoms and physical exam findings — gives clinicians more confidence than either result alone.

Conditions ESR helps detect and monitor

ESR is a non-specific test, but it has well-established roles across several condition categories. It cannot diagnose any single disease on its own, and a normal ESR does not rule out an inflammatory illness. With those limits in mind, here is how it is commonly used.

Autoimmune and rheumatologic conditions

Polymyalgia rheumatica and giant cell arteritis typically affect adults older than 50. ESR is useful in diagnosing both. One classic study reported an average ESR exceeding 90 mm/hr in patients with temporal arteritis, with values greater than 30 mm/hr in 99% of cases — though a normal ESR does not exclude the diagnosis.
Rheumatoid arthritis and systemic lupus erythematosus: ESR is frequently used to support the diagnosis and follow disease activity, although correlation with clinical disease activity is imperfect, and some patients with active synovial inflammation can have a normal ESR.
Systemic vasculitis of various types: elevated ESR is a common finding.

Infections

ESR can rise with both acute and chronic infections, and infection is the leading cause of extreme elevation above 100 mm/hr. In osteomyelitis (bone infection) and septic arthritis, elevated ESR may aid diagnosis and follow-up, though sensitivity varies between studies. In children, an ESR threshold of 20 mm/hr has been reported with 94% sensitivity for detecting bacterial bone or joint infection at admission.

Inflammatory bowel disease

Crohn’s disease and ulcerative colitis can drive elevated ESR, and the test is one of several markers used to help monitor disease activity over time. CRP, fecal calprotectin, and imaging typically play larger diagnostic roles, but ESR remains a low-cost adjunct.

Cancer

In oncology, an elevated ESR has been associated with worse prognosis across several cancer types, including cutaneous melanoma, breast, prostate, colorectal, Hodgkin lymphoma, and chronic lymphocytic leukemia. Markedly elevated values can also be seen with multiple myeloma and lymphoplasmacytic lymphoma (Waldenström macroglobulinemia).

Cardiovascular disease

Elevated ESR has been linked to coronary artery disease, likely through the inflammatory pathophysiology of atherosclerosis. In ischemic stroke, ESR may correlate with the extent of brain injury and short-term outcomes. ESR is not a primary cardiovascular screening tool, but it can be part of a broader inflammatory workup.

When to talk to your doctor

ESR is rarely interpreted in isolation. Reach out to your clinician if any of the following apply:

Your ESR is above 100 mm/hr on a single test — this strongly suggests an underlying condition such as infection, multiple myeloma, lymphoma, giant cell arteritis, polymyalgia rheumatica, or hypersensitivity vasculitis and warrants prompt evaluation.
Your ESR is persistently elevated above your age- and sex-specific reference range on repeat testing, even without obvious symptoms — this can justify further investigation to rule out occult disease.
You are over 50 and have new headaches, jaw pain when chewing, scalp tenderness, or vision changes, especially with an elevated ESR — these are warning signs of giant cell arteritis, which requires urgent assessment to prevent permanent vision loss.
You have shoulder or hip-girdle stiffness and pain lasting weeks, particularly in adults over 50 — this combination raises concern for polymyalgia rheumatica.
You have unexplained fever, unexplained weight loss, joint stiffness, neck or shoulder pain, loss of appetite, or anemia alongside an elevated ESR.
Your ESR is normal, but you have ongoing symptoms of infection or inflammatory disease — a normal value does not rule out localized infection or active inflammation, and additional testing may still be warranted.
You have a known inflammatory condition (rheumatoid arthritis, IBD, vasculitis) and your ESR is rising despite treatment — this can suggest a flare or treatment response that needs attention.

Bring a complete medication and supplement list to your appointment, since several common drugs — including statins, NSAIDs, and valproic acid — can lower ESR readings and may mask underlying inflammation.

Frequently asked questions

Do I need to fast for an ESR test?

No. MedlinePlus states you do not need any special preparations for an ESR test. If your provider has ordered other blood tests at the same time, those tests may require fasting — your provider will tell you if there are special instructions to follow.

Is ESR the same as “sed rate”?

Yes. “Sed rate” is short for sedimentation rate, and both terms refer to the same test. Other names include ESR, SED rate, sedimentation rate, and Westergren sedimentation rate. Your lab report may use any of these terms interchangeably, and the result is reported in mm/hr.

What’s the difference between ESR and CRP?

ESR measures how fast red blood cells settle, which depends on plasma proteins like fibrinogen. CRP directly measures one specific acute-phase protein made by the liver during inflammation. The two are commonly ordered together because they provide complementary information — CRP is less affected by red blood cell abnormalities, while ESR is useful for slower-moving trends.

Can my ESR be normal even when I’m sick?

Yes. A normal ESR does not exclude an inflammatory illness. Some patients with active rheumatoid arthritis, severe infections, or even malignancies can have normal ESR readings. Normal ESR can also occur with localized infections that do not produce a strong systemic acute-phase response.

What does “ESR Westergren” on my report mean?

It means your lab used the Westergren method, the international reference standard for measuring ESR for nearly a century. Whole blood is placed in a standardized vertical tube, and the distance red cells settle in one hour is reported in mm/hr. Reference ranges in your report should match this method.

How long do ESR results take?

The blood draw itself takes less than five minutes. The traditional Westergren test takes about an hour to run in the lab once the sample arrives. Modern automated systems can produce results within five minutes of processing. Most patients receive results back within one business day, depending on the lab.

Can medications affect my ESR?

Yes. Several medications are known to lower ESR readings, including valproic acid, statins, and nonsteroidal anti-inflammatory drugs (NSAIDs). Lifestyle factors also matter — regular alcohol consumption and habitual moderate-to-high physical activity are both associated with lower ESR values. Tell your provider about all medications and supplements you take so the result can be interpreted in context.

References

Last reviewed: 2026-05-17