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Red Blood Cell Sedimentation Rate (Erythrocyte Sedimentation Rate)

Published: August 9, 2026Updated: August 17, 2026

This test measures how quickly red blood cells settle in a tube of blood over time. It can help identify conditions affecting blood flow or inflammation.

Quick summary

["ESR helps detect inflammation or blood-related disorders by tracking red blood cell settling speed."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
30341-2
Short code
Erythrocyte Sed Rat Bld
Synonyms
Erythrocyte Sed Rat Bld
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Ref low
4.2
Ref high
5.9
Critical range
2 N/A – 7 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
85041
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What ESR Measures

ESR evaluates the rate at which red blood cells clump together and settle at the bottom of a test tube. This clumping is influenced by proteins like fibrinogen, which can be elevated in inflammatory conditions.

Why ESR Might Be Ordered

Your doctor may recommend an ESR to check for conditions like infections, autoimmune diseases (e.g., rheumatoid arthritis), or other inflammatory processes. It’s often used as part of a broader evaluation.

How ESR Works

Blood is collected in a tube, mixed, and left undisturbed. After a set time (typically 1 hour), the distance the red blood cells have settled is measured. This distance is reported in millimeters per hour (mm/hr).

What Normal Results Mean

While reference ranges vary by lab, higher ESR values often suggest inflammation or infection. Lower values may indicate normal blood flow or certain blood disorders.

Reference range

Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A

Specimen: whole-blood

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

ESR is a simple, non-invasive test that provides a general indicator of inflammation. Elevated ESR can signal conditions like infections, autoimmune diseases, or other systemic issues. However, it’s not specific to any single condition and should be interpreted alongside other clinical findings and symptoms.

Short name

ESR

Frequently asked questions

What causes ESR to be high?
ESR can be elevated due to infections (like pneumonia or urinary tract infections), autoimmune diseases (like lupus or rheumatoid arthritis), or other inflammatory conditions. Stress, pregnancy, or certain medications may also temporarily affect it.
What causes ESR to be low?
Low ESR may occur in conditions like polycythemia (high red blood cell count), certain blood disorders, or in people with very low protein levels (e.g., malnutrition). It can also be normal in some individuals.
Does ESR replace other tests?
No, ESR is a general screening tool. It should be used alongside other tests (like C-reactive protein or blood counts) and clinical symptoms to guide diagnosis. Your doctor will interpret results in the context of your overall health.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy