The C-Reactive Protein (CRP) test is a common blood test that measures the amount of C-reactive protein in your bloodstream. CRP is made by the liver and is considered a biomarker of inflammation. When your body has inflammation—often from an infection, an injury, or an autoimmune disease—CRP levels can rise quickly, sometimes within hours.

CRP is a non-specific marker, meaning it tells your clinician that inflammation is present somewhere in the body, but it does not pinpoint the exact cause or location. In general, higher CRP levels suggest more active inflammation. Mild elevations can be seen with many common conditions, while very high results are more often linked to significant infection or severe inflammation. Doctors often interpret CRP results alongside your symptoms, exam findings, and other labs (such as a complete blood count, ESR, cultures, or imaging) to reach a diagnosis and to monitor response to treatment.

Depending on your situation, your clinician may order a standard CRP test for inflammation and infection. In some cases, a different version called high-sensitivity CRP (hs-CRP) may be used to help estimate heart disease and cardiovascular risk; hs-CRP measures lower CRP levels than the standard test.

A CRP test is typically ordered when a healthcare professional needs to check for inflammation in the body, evaluate possible infection, or track how well a treatment is working. Because CRP can rise and fall relatively quickly, it is often useful for monitoring changes over time.

Your doctor may recommend a CRP test if you have symptoms that could point to inflammation or infection, such as:

Fever or chills, fatigue, body aches, unexplained weakness, rapid heartbeat, new or worsening pain, redness or swelling in a specific area, persistent cough or shortness of breath, abdominal pain, or symptoms suggesting a flare of an autoimmune condition (for example, worsening joint pain and morning stiffness).

It may also be ordered to:

Help distinguish whether symptoms are more likely related to an inflammatory process, monitor chronic inflammatory or chronic disease activity (such as rheumatoid arthritis), assess response to antibiotics or anti-inflammatory medications, evaluate possible post-surgical or hospital-related infection, or follow inflammatory bowel disease activity when symptoms change.

If your clinician is focused on cardiovascular prevention, they may order hs-CRP to help refine overall heart disease risk—especially when considered together with cholesterol levels, blood pressure, diabetes status, smoking history, and family history.

• Acute and chronic infections (bacterial infections, pneumonia, urinary tract infection, skin/soft tissue infection)
• Sepsis and other severe systemic infections
• Rheumatoid arthritis
• Systemic lupus erythematosus and other autoimmune diseases
• Inflammatory bowel disease (Crohn’s disease, ulcerative colitis)
• Vasculitis and other inflammatory disorders
• Osteomyelitis (bone infection) and septic arthritis
• Postoperative inflammation or complications (including suspected infection after surgery)
• Cardiovascular disease risk assessment (using high-sensitivity CRP as a biomarker)

• Identifying and monitoring inflammation when you have persistent, unexplained symptoms
• Tracking autoimmune disease activity (e.g., rheumatoid arthritis) and response to treatment
• Evaluating possible infection and monitoring recovery during treatment
• Monitoring chronic inflammatory conditions over time to help prevent flares and complications
• Supporting cardiovascular health planning (hs-CRP as part of overall heart disease risk assessment)
• General wellness check-ins when combined with other diagnostic tests to understand overall inflammatory status