To test for inflammation in the body, doctors most often use a blood test for CRP, often with a sed rate (ESR). Neither test can name a disease on its own, so both are read next to your symptoms and an exam. For heart risk, a version called hs-CRP is used, but expert groups disagree on who needs it.
First, what are you trying to find?
Inflammation is part of how your body handles an injury or an infection. Short bursts of it are critical for survival.
The worry is a different kind: a low level that stays switched on for months or years. Scientists call it systemic chronic inflammation. A 2019 review linked it to heart disease, cancer, diabetes, kidney disease, fatty liver disease, and autoimmune and brain diseases.
Here is the catch. A blood test sees the signal, not the source. The common ones can flag inflammation from many different problems, and they can miss some too. So skip "do I have inflammation?" Ask instead: what am I trying to rule in, or rule out?
What blood test shows inflammation? Start with CRP
CRP, short for C-reactive protein, is a blood marker of inflammation across the whole body. It is one of the two most widely used lab tests for inflammation. Doctors use it to help diagnose a problem, to guide treatment and to predict disease.
One high CRP reading is a reason to talk and maybe retest, not a verdict.From a 2024 meta-analysis in PLoS One
A 2016 review of CRP and the sed rate gave a plain warning. Both tests lack sensitivity or specificity. In everyday words, they can miss a problem, and they can flag one that isn't the problem your doctor is looking for. The review said they should only be used with your history and a physical exam.
So what moves CRP in people who feel fine? A 2021 study tested 1,472 adults in Spain with no known inflammatory disease. Body mass index (BMI), a measure of weight for height, was the main thing tied to their CRP levels.
hs-CRP: the version for heart risk
High-sensitivity CRP, or hs-CRP, is the version heart doctors use to measure chronic, low-grade inflammation.
The link to heart risk is solid. A 2010 analysis pooled the records of 160,309 people without heart disease from 54 long-term studies. A CRP level three times higher went with a 37% higher risk of coronary heart disease, even after accounting for the usual risk factors. Higher CRP was also linked to stroke, and to deaths from heart disease, several cancers and lung disease.
Who should get the test is less settled. In 2018, the US Preventive Services Task Force, a panel that judges screening tests, looked at adding hs-CRP to standard heart risk scores. It found only small gains. It said the evidence was not enough to weigh the benefits and harms for adults with no symptoms.
A 2025 statement from the American College of Cardiology took a firmer line. It said a high hs-CRP in apparently healthy people marks a higher-risk group. In that group, statin treatment lowered the risk of first major heart events, even when LDL cholesterol was normal. If heart risk is your question, this is a test worth asking about.
The sed rate (ESR): older and broader
The sed rate is the other classic blood test for inflammation. Its full name, erythrocyte sedimentation rate, describes what the lab watches: how fast red blood cells settle in a tube.
CRP and the sed rate often disagree. The 2016 review found these mismatches are common, maybe most of all in long-term inflammatory diseases.
The Spanish study showed how this plays out. Of the 1,472 adults, 1,123 had normal results on both tests. But 208 had a high CRP with a normal sed rate, a pattern tied to higher BMI. Another 72 had a high sed rate with a normal CRP, a pattern tied to older age. When the two tests disagree, weight and age may be part of the story.
Other tests you may hear about
Ferritin. This is the main blood test for iron stores. But infection and inflammation make it hard to read. In surveys of 24,844 women aged 15 to 49, only 6% of those with the highest CRP looked low on iron by ferritin, against 29% of those with the lowest CRP. Researchers adjust ferritin for CRP to correct for this.
Fecal calprotectin. This stool test looks for inflammation in the gut. A 2023 meta-analysis, which pools many studies, combined 17 studies with 1,956 patients. The test picked up 85.8% of people with inflammatory bowel disease (IBD) and correctly cleared 91.7% of people with irritable bowel syndrome (IBS). Its real strength is a normal result. Where IBD affects 1% of people, a negative test was right 99.8% of the time, but a positive one was right only 9% of the time.
Why one result is never the whole story
Your CRP is not a fixed number. A 2024 review of 60 studies looked at people tested more than once. It found that CRP and hs-CRP both varied a lot within the same person. The authors noted that many of those studies were small. Still, the message is clear: one high reading is a reason to talk and maybe retest, not a verdict.
What this means for you
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you have a fever, new joint swelling, blood in your stool, weight loss you can't explain, or symptoms that keep coming back. Ask first, too, if you are pregnant, have kidney disease or an autoimmune condition, or take medicines that affect your immune system. If you take a prescribed medicine, keep taking it as prescribed and talk to your provider before changing it based on any test result.
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The bottom line
Each test answers a narrower question than the word "inflammation" suggests. CRP and the sed rate flag that something is going on. hs-CRP speaks to heart risk. Ferritin and calprotectin answer questions about iron and the gut. None of them can read chronic inflammation alone, and a single result can swing. The best test is the one that fits the question you and your provider are asking. Start there, and let the number follow.
Common questions
What blood test shows inflammation?
The most common one is CRP, short for C-reactive protein, often ordered with the sed rate (ESR). They are the two most widely used blood tests for inflammation in the body. Neither can tell you where the inflammation is or what it means on its own, so doctors read them with your history and an exam.
What is the best test for inflammation?
It depends on the question. For general inflammation, CRP is the usual first test. For heart risk, hs-CRP is the version cardiologists use, though US expert groups disagree on testing healthy adults. For gut symptoms, a stool test called fecal calprotectin is very good at ruling out inflammatory bowel disease.
Can a blood test detect chronic inflammation?
Partly. A raised hs-CRP is the most common sign of chronic, low-grade inflammation, and across 54 studies higher CRP was linked to heart disease, stroke and earlier death. But CRP is not specific, and it varies within the same person. So one reading is a clue, not a diagnosis.
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How this article was made
Researched and written from 9 peer-reviewed papers. Our automated check matched every claim against the exact words of its source, confirmed every paper exists in PubMed, and found none retracted. Checked November 2, 2026. Not individually reviewed by a doctor. Photos are illustrative; the people in them are not patients or readers.
Grades run Strong, Moderate, Emerging, Early and Not supported, and the grade decides the words we may use. How we grade evidence · Medical disclaimer
Sources
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- Cross-sectionalC-Reactive Protein versus Erythrocyte Sedimentation Rate: Implications Among Patients with No Known Inflammatory Conditions.Alende-Castro V, Alonso-Sampedro M, Fernández-Merino C et al. J Am Board Fam Med, 2021.PubMedFull paper
- Cross-sectionalAdjusting ferritin concentrations for inflammation: Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) project.Namaste SM, Rohner F, Huang J et al. Am J Clin Nutr, 2017.PubMedFull paper
- Meta-analysisC-reactive protein concentration and risk of coronary heart disease, stroke, and mortality: an individual participant meta-analysis.Kaptoge S, Di Angelantonio E, Lowe G et al. Lancet, 2010.PubMedFull paper
- GuidelineRisk Assessment for Cardiovascular Disease With Nontraditional Risk Factors: US Preventive Services Task Force Recommendation Statement.Curry SJ, Krist AH, Owens DK et al. JAMA, 2018.PubMedFull paper
- ReviewInflammation and Cardiovascular Disease: 2025 ACC Scientific Statement: A Report of the American College of Cardiology.Mensah GA, Arnold N, Prabhu SD et al. J Am Coll Cardiol, 2026.PubMedFull paper
- Meta-analysisWithin-subject variation of C-reactive protein and high-sensitivity C-reactive protein: A systematic review and meta-analysis.Gough A, Sitch A, Ferris E et al. PLoS One, 2024.PubMedFull paper
- ReviewChronic inflammation in the etiology of disease across the life span.Furman D, Campisi J, Verdin E et al. Nat Med, 2019.PubMedFull paper
- Meta-analysisSystematic review with meta-analysis: Diagnostic performance of faecal calprotectin in distinguishing inflammatory bowel disease from irritable bowel syndrome in adults.Dajti E, Frazzoni L, Iascone V et al. Aliment Pharmacol Ther, 2023.PubMedFull paper
