CRP vs ESR - what's the difference?
Both are inflammation markers, but they respond differently: CRP fast, ESR slow. Here's when each is more useful.
CRP
An acute-phase protein that rises within hours of inflammation and falls just as fast. A sensitive, "fast" marker.
ESR
The erythrocyte sedimentation rate - rises more slowly and lingers longer. A non-specific, "slow" marker.
CRP vs ESR
| C-Reactive Protein (CRP) | Erythrocyte Sedimentation Rate (ESR) | |
|---|---|---|
| Unit | mg/L | mm/hr |
| Typical adult range | < 3 mg/L | Men < 15; women < 20 mm/hr |
| Common reasons for a high value | Bacterial infection; Active autoimmune disease | Active infection or inflammation; Autoimmune disease flare |
| Common reasons for a low value | No active inflammation; A low CRP is a strong negative predictor | Polycythaemia; Sickle cell disease, hereditary spherocytosis |
Key differences
- CRP responds in hours; ESR over days and stays elevated longer.
- Both are non-specific: they show inflammation, not its cause.
- They're often read together for a fuller picture.
- CRP is less affected by age/sex/anemia than ESR.
Bottom line
CRP is fast and sensitive, ESR slow and sluggish to change. Together they give a fuller picture of inflammation; read with your doctor.
Frequently asked questions
Which is better?
It depends on the question. CRP reflects current inflammation, ESR a more drawn-out process. Both are often ordered.
Can they disagree?
Yes - at an acute onset CRP is already high while ESR isn't yet; while it's resolving, the reverse.
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