Erythrocyte Sedimentation Rate (ESR)
ESR is a non-specific inflammation marker measured by watching how fast red blood cells settle in a column. Slow but very sensitive to chronic systemic inflammation.
What it measures
ESR is the rate at which red blood cells sediment in a vertical column of anticoagulated blood over one hour. Acute-phase proteins (especially fibrinogen) make cells clump and fall faster, so ESR rises in many inflammatory states. It's slower to move than CRP — both up and down — which is why the two are often ordered together: CRP for the acute picture, ESR for chronic inflammatory monitoring. Hugely useful in giant-cell arteritis, polymyalgia rheumatica and rheumatologic flare-tracking, where dramatic elevations (>100 mm/hr) are common.
What a high value can mean
- Active infection or inflammation — bacterial > viral; pneumonia, osteomyelitis, abscess.
- Autoimmune disease flare — rheumatoid arthritis, lupus, polymyalgia rheumatica.
- Giant-cell (temporal) arteritis — ESR almost always >50 mm/hr; sight-threatening if missed.
- Malignancy — myeloma, lymphoma, metastatic cancer.
- Chronic kidney disease, end-stage renal failure — ESR rises non-specifically.
- Pregnancy, anaemia, advanced age — physiological elevations.
What a low value can mean
- Polycythaemia — more red cells slow the fall.
- Sickle cell disease, hereditary spherocytosis — abnormal cell shape resists clumping.
- Congestive heart failure, severe hypofibrinogenaemia — protein patterns lower the rate.
- A low ESR by itself is not clinically actionable.
When to discuss with a doctor
ESR >50 mm/hr in an older patient with new headache, scalp tenderness or jaw pain is a same-day rheumatology consultation — suspected giant-cell arteritis. ESR + CRP together that don't return to normal after a treated infection raise the question of a persistent cause. Mediora.AI shows the value in context; ESR alone is not a diagnostic test.