CRP
C-reactive protein
CRP is made by the liver during inflammation. It rises and falls quickly, which makes it useful for detecting an active process and for judging whether other markers can be trusted.
Reference range
mg/L- Women
- under 5 mg/L
- Men
- under 5 mg/L
Reference ranges differ between laboratories and assays. Always read your result against the range printed on your own report.
What CRP measures
When inflammation starts anywhere in the body, signalling molecules reach the liver, which responds by producing C-reactive protein. Levels can rise a thousandfold within a day or two and fall just as quickly once the cause resolves.
That speed is both its strength and its limit. CRP tells you that something inflammatory is happening and roughly how intense it is, but it says nothing about where or why. A chest infection and an autoimmune flare can produce the same number.
A separate high-sensitivity assay, hs-CRP, measures the low end of the range precisely and is used in cardiovascular risk assessment rather than for detecting infection.
Why it gets tested
To detect or monitor infection and inflammatory disease, to follow recovery after surgery, and — as hs-CRP — as one component of cardiovascular risk assessment. It is also measured alongside ferritin to check whether a normal ferritin can be believed.
Commonly associated with low values
- No detectable inflammatory activity at the time of the test
Commonly associated with high values
- Bacterial infection, typically producing the highest values
- Autoimmune or inflammatory disease during a flare
- Tissue injury, including after surgery
- Persistent mild elevation in obesity and metabolic syndrome
What can shift the result
- Intense exercise in the preceding days raises CRP
- A minor cold at the time of testing is enough to lift the value
- Combined oral contraceptives and hormone therapy raise baseline CRP
Questions
What is the difference between CRP and hs-CRP?
They measure the same protein with different precision. Standard CRP is designed to detect the large rises seen in infection and inflammation. High-sensitivity CRP resolves the low end of the range accurately and is used to assess cardiovascular risk, where the differences of interest are small.
Does a raised CRP mean something serious?
Not on its own. CRP indicates that an inflammatory process is active, not what is causing it — a common cold, a recent hard training session or a healing injury all raise it. It is interpreted in the context of symptoms and other findings, never alone.
Have your CRP result in front of you?
Upload the report and see every value in its reference range, not just this one. No account needed.
Analyze my lab reportOften measured alongside
This page is general information about a laboratory value. It is not a diagnosis and does not replace medical advice. Discuss your own results with a doctor, who can read them in the context of your history and symptoms.