CRP vs ESR: what's the difference?
Educational — not medical advice · Ranges vary between laboratories
The short answer: Both say inflammation is present somewhere in the body without saying where or why. CRP is the fast one, rising within hours of an infection or injury and falling just as quickly once the trigger settles. ESR moves more slowly and reflects changes across days to weeks.
CRP is a protein your liver produces in response to inflammatory signals, and it rises and falls quickly, making it a good marker for tracking how an infection or flare-up is progressing in near real time. It's less useful for chronic, low-grade inflammation, which is where the specialized hs-CRP version comes in.
Full CRP guideESR is one of medicine's oldest tests: red blood cells are left to settle in a tall thin tube for an hour, and inflammation-related proteins make them clump and fall faster. It's a blunt but useful signal that something inflammatory is going on, used more to track a known condition than to diagnose a new one.
Full ESR guideAt a glance
| CRP | ESR | |
|---|---|---|
| Panel | Inflammation | Inflammation |
| Unit | mg/L | mm/hr |
| Typical adult range | Normal 0–5 mg/L | Normal 0–20 mm/hr |
| Also known as | C-Reactive Protein | Erythrocyte Sedimentation Rate, Sed Rate |
General adult reference intervals — your lab's printed range takes precedence.
Why they're often tested together
That timing difference is the point of running both: CRP tracks the current flare in near real time while ESR shows the slower background. CRP under about 5 mg/L and ESR under about 20 mm/hr are typical adult marks, though ESR normally creeps up with age and runs a little higher in women.
Questions people ask
Can one be raised while the other looks normal?
Yes, and timing is a common reason: CRP can already be climbing while ESR still reads normal early on, or ESR can stay elevated after CRP has settled. Age, pregnancy, and chronic kidney disease can also lift ESR on their own.
How is hs-CRP different from standard CRP?
It measures the same protein at much lower concentrations, and it's used to estimate cardiovascular risk rather than to detect acute infection. Typical bands are under 1 mg/L, 1–3 mg/L, and above 3 mg/L, read alongside cholesterol and other risk factors.
More comparisons
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