Erythrocyte Sedimentation Rate (ESR) Test
The Erythrocyte Sedimentation Rate (ESR) test measures how quickly red cells settle in anticoagulated whole blood over one hour, providing an indirect, slow-responding marker of inflammation. A raised ESR reflects an inflammatory, infective, autoimmune, or neoplastic process without indicating its cause, and it has specific diagnostic value in polymyalgia rheumatica and giant cell arteritis.
1
Biomarkers
Blood (whole blood)
Sample
1–2 business days
Turnaround
No
Fasting
What is the ESR test?
The Erythrocyte Sedimentation Rate Test measures how quickly red cells settle in a column of anticoagulated whole blood over one hour, providing an indirect, well-established index of the acute-phase inflammatory response. Because the rate is driven by plasma proteins such as fibrinogen and immunoglobulins, a raised ESR reflects an inflammatory, infective, autoimmune, or neoplastic process without indicating its cause. In the diagnostic landscape, ESR is one of the oldest and most widely available inflammatory markers and is frequently paired with C-reactive protein, which responds faster and more directly. ESR's slower kinetics make it well suited to monitoring chronic inflammatory disease over time, and it retains specific diagnostic importance in polymyalgia rheumatica and giant cell arteritis, where marked elevation supports the diagnosis. Practitioners order it to screen for and monitor inflammation, to support specific rheumatological diagnoses, and to track disease activity, interpreting the result with the clinical context and the many non-inflammatory factors that influence it.
What does the ESR test measure?
The erythrocyte sedimentation rate measures the distance red cells fall in a vertical column of anticoagulated whole blood over one hour. The rate is governed largely by plasma proteins, especially fibrinogen and immunoglobulins, which reduce the negative surface charge on erythrocytes and promote rouleaux formation, causing cells to settle faster. It is therefore an indirect, slow-responding indicator of the acute-phase response, rising and falling over days rather than hours.
ESR is a non-specific marker of inflammation used to detect and monitor inflammatory, infective, autoimmune, and neoplastic conditions. It is most useful where its slow kinetics suit chronic disease monitoring, and it has specific diagnostic roles in conditions such as polymyalgia rheumatica and giant cell arteritis. Because it is influenced by many non-inflammatory factors, it is interpreted alongside the clinical picture and often with CRP.
Why is the ESR test ordered?
- Investigation of suspected polymyalgia rheumatica or giant cell arteritis, where a markedly raised ESR supports the diagnosis
- Screening for and monitoring of inflammatory and autoimmune conditions such as rheumatoid arthritis and connective tissue disease
- Assessment of suspected chronic infection or inflammation in patients with non-specific systemic symptoms
- Monitoring of disease activity over time in chronic inflammatory disorders, where ESR's slow kinetics are advantageous
- Investigation of unexplained anaemia, weight loss, or constitutional symptoms where an inflammatory or neoplastic process is considered
- Support for the diagnosis and follow-up of conditions such as osteomyelitis or other deep-seated infections, alongside imaging and CRP
- Evaluation of patients where a low-cost, widely available inflammatory marker is needed to complement CRP
Sample collection and turnaround
Sample type
Blood (whole blood)
Fasting required
No
Collection method
Venipuncture at patient service centre
Turnaround
1–2 business days
Collection notes
Collected into the anticoagulant tube specified by the laboratory (commonly EDTA or sodium citrate). The test is time-sensitive and should be performed within the validated interval after collection, as delayed processing alters sedimentation. # REVIEWER FLAG: Confirm exact tube type and stability window with Access Medical Laboratories before publication.
Specimen requirements
Anticoagulated whole blood per laboratory protocol. Analyse within the validated post-collection interval. # REVIEWER FLAG: Confirm minimum volume and processing window with Access Medical Laboratories.
What can affect ESR results?
ESR rises physiologically with age and is higher in women, so age- and sex-adjusted reference ranges must be applied to avoid misclassifying a normal value as raised.
A reduced red cell concentration alters the cell-to-plasma ratio and accelerates sedimentation, raising ESR independent of inflammation and limiting interpretation in anaemic patients.
Physiological increases in fibrinogen and plasma volume during pregnancy raise ESR without indicating pathology.
A high red cell concentration, and conditions such as sickle cell disease or spherocytosis that impair rouleaux formation, slow sedimentation and lower ESR even when inflammation is present.
Delayed processing and storage temperature affect sedimentation; the test should be performed within the validated interval after collection to avoid artefact. # REVIEWER FLAG: Confirm Access Medical Laboratories specimen stability window.
Very high fibrinogen or a monoclonal paraprotein, as in myeloma, can produce strikingly elevated ESR through enhanced rouleaux formation, sometimes out of proportion to clinical inflammation.
What do ESR results mean?
Elevated
A raised ESR indicates an acute-phase response and is consistent with inflammation, infection, autoimmune disease, or malignancy, but does not identify the cause. Very high values (often >100 mm/hr) narrow the differential towards giant cell arteritis, marked infection, myeloma, or other significant pathology and warrant focused evaluation.
Normal
A normal age- and sex-adjusted ESR reduces the likelihood of significant active inflammation but cannot exclude it, especially given ESR's slow kinetics. It is interpreted with the clinical picture and frequently alongside CRP, which responds earlier.
Reduced
A low ESR is generally unremarkable but can be falsely low in polycythaemia, hypofibrinogenaemia, and red cell shape abnormalities that impair rouleaux formation. A normal or low ESR does not exclude active disease, particularly early in an acute process where CRP may already be rising.
Note: ESR is non-specific and slow to change, so it is interpreted with the clinical context and usually with CRP rather than in isolation. Numerous non-inflammatory factors — age, sex, anaemia, pregnancy, red cell disorders, and paraproteins — influence the result and can mislead. Age- and sex-adjusted reference ranges are essential, and discordance with CRP is itself informative.
Frequently asked questions
It measures how quickly red cells settle in a column of anticoagulated whole blood over one hour. The rate is driven by plasma proteins such as fibrinogen, so a raised ESR reflects inflammation without identifying its cause.
How to access the ESR test
The ESR reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.
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Published: June 3, 2026
Last reviewed: June 3, 2026
- Harrison M. Erythrocyte sedimentation rate and C-reactive protein. Aust Prescr. (2015)
- Bray C, et al. Erythrocyte Sedimentation Rate and C-reactive Protein Measurements and Their Relevance in Clinical Medicine. WMJ. (2016)
- Dejaco C, et al. 2015 Recommendations for the management of polymyalgia rheumatica: EULAR/ACR collaborative initiative. Ann Rheum Dis. (2015)
- Brigden ML. Clinical utility of the erythrocyte sedimentation rate. Am Fam Physician. (1999)
This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.