C-Reactive Protein (CRP)
Measures inflammation in the body.
Content last reviewed 2026-09-12 · Educational information — not medical advice
It is commonly considered when evaluating Pneumonia, Irritable Bowel Syndrome, Meningitis; people with Fever, Fatigue, Dyspnea may have it ordered as part of their work-up.
What is the C-Reactive Protein (CRP)?
The C-Reactive Protein (CRP) is a laboratory blood test that measures C-reactive protein (CRP), a general inflammation marker produced by the liver.
How the C-Reactive Protein (CRP) works
Blood assays of acute-phase reactants — proteins whose levels swing upward with systemic inflammatory activity.
Why healthcare providers order it
Unexplained fever or fatigue workups, inflammatory-bowel-disease activity tracking, cardiovascular-risk refinement (hs-CRP), infection response monitoring, and autoimmune-disease activity assessment.
Interpreting your results
Understanding inflammation markers
- They scream 'inflammation', not 'where': localization requires clinical context and other investigations.
- Transient spikes are normal — a cold, dental work, hard workouts, even poor sleep nudge them; persistently elevated values demand explanation.
- hs-CRP vs standard CRP: same protein, finer assay — hs-CRP grades subtle vascular-risk inflammation; standard CRP tracks overt inflammation.
What your CRP result means
If high: Elevated CRP confirms active inflammation somewhere in the body; it cannot localize the source. Marked spikes accompany infections.
Reference intervals vary by laboratory, instrument, age, sex, and — for hormones — collection time. Always compare your value against the range printed on your own report, and review results with a qualified healthcare professional who knows your history. This guide is educational and does not diagnose.
Understanding your lab report
- Find the reference interval printed beside your value on the report — that pairing defines 'normal' for this lab run.
- Note the units. mmol/L vs mg/dL, ng/mL vs µg/L — numbers mean nothing across unit systems.
- Look at flags (H/L) but read the degree: barely-outside values behave differently than multiples of the limit.
- Trends outrank snapshots. A series of results tells your provider far more than any single draw.
Conditions that may involve C-Reactive Protein (CRP)
Symptoms that may lead to this test
Frequently asked questions
What does the C-Reactive Protein (CRP) measure?
It measures C-reactive protein (CRP), a general inflammation marker produced by the liver.
What does a high CRP result mean?
Elevated CRP confirms active inflammation somewhere in the body; it cannot localize the source. Marked spikes accompany infections.
Do I need to fast before the C-Reactive Protein (CRP)?
Fasting is not routinely required for this test; follow any instructions from your provider or laboratory.
How soon do C-Reactive Protein (CRP) results come back?
Most routine assays return within 1–3 business days; specialty methods can extend that to a week or more.
Can an abnormal C-Reactive Protein (CRP) result mean something serious?
Abnormal results range from benign to urgent; degree, direction, and trend — reviewed by a clinician who knows your history — determine what happens next.
Sources & data provenance
- Family-specific guidance compiled from standard clinical laboratory medicine references