CRP and hs-CRP measure the same protein. A standard CRP test is used to find and follow active inflammation, such as an infection or an injury. The high-sensitivity (hs) version reads much smaller amounts, so it is used to judge heart risk: under 1 mg/L is lower risk, 1 to 3 is average, over 3 is higher.
This article is part of our series on testing for inflammation. For every test and what each one shows, start with [How to test for inflammation](/articles/how-to-test-for-inflammation).
One protein, two kinds of test
C-reactive protein, or CRP, was found in 1930 in the blood of people with pneumonia. For years, scientists thought healthy people didn't have any. Then they learned it is always there in trace amounts.
Your liver makes CRP when immune signals such as IL-6 (a messenger protein that cells release when they are inflamed) tell it to. When something big is going on, like a serious infection or an injury, the level climbs fast. That is what a standard CRP test is built to catch. It is widely used to find and follow sepsis, trauma and other inflammatory conditions.
Over the last few decades, labs got better at measuring it. Tests moved from rough yes-or-no checks to high-sensitivity assays. That opened a new use. The hs test can pick up the quiet, low-level inflammation that sits under clogged arteries, long before anyone feels sick.
So the protein never changed. The ruler did.
What is a standard CRP test for?
Think of the standard test as a smoke alarm for the whole body. It tells your doctor something is inflamed. It does not say where or why. A 2016 review warned that CRP is not specific enough to diagnose anything by itself. It should be read along with your history and an exam.
The protein never changed. The ruler did.From a 2023 review in Clin Chem Lab Med
A 2022 Cochrane review pooled 12 trials with 10,218 people who saw a primary care doctor for a cough, cold or other airway infection. When doctors had a quick CRP test on hand, antibiotic prescriptions fell from 516 to 397 per 1,000 people. Recovery within 7 days was about the same.
When is hs-CRP ordered?
hs-CRP is mostly ordered to help judge your chance of a heart attack or stroke. A 2016 review in a leading cardiology journal said it adds about as much to that picture as blood pressure or cholesterol. It gave three bands: under 1 mg/L means lower risk, 1 to 3 means average, and over 3 means higher risk.
At the time, U.S. guidelines gave it a weak (class IIb) rating. The review said it fits best when a person and their doctor are unsure whether to start a cholesterol-lowering statin. In a large trial of people with normal LDL cholesterol but hs-CRP above 2 mg/L, a statin lowered first heart attacks, strokes and heart deaths by 47%.
In 2025, the American College of Cardiology went further. Its scientific statement says high hs-CRP in people who seem healthy marks a higher-risk group. It calls the link between inflammation and clogged arteries "clinically actionable."
Is hs-CRP more accurate than CRP?
Not more accurate. More sensitive at the low end. The hs test earns its keep in the range where healthy-looking people differ from one another.
That range matters. A 2010 analysis pooled 54 long-term studies with 160,309 people who had no heart disease at the start. Each threefold step up in CRP was linked to a 37% higher risk of heart disease after accounting for other risk factors. It was also linked to stroke, and to death from some cancers and lung disease.
The Women's Health Study followed 27,939 healthy U.S. women for 30 years. Women in the top fifth for hs-CRP had about 1.7 times the risk of a first major heart event as women in the bottom fifth. For LDL cholesterol, the gap was 1.36 times.
Why one number isn't the whole story
hs-CRP moves around. A study of 56,218 adults in China tested it twice, two years apart. The two readings matched less closely than blood pressure, cholesterol or blood sugar did. Many things besides heart risk can push CRP up or down, including conditions that have nothing to do with infection.
And the experts are split. In 2018, the U.S. Preventive Services Task Force found that adding hs-CRP to standard risk scores made only small gains in sorting people by risk. It found too little evidence on whether test-guided treatment leads to fewer heart attacks or deaths. The 2025 cardiology statement reads the evidence more boldly. That gap is part of why we grade this Moderate.
What this means for you
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your hs-CRP is over 3 mg/L; you had a recent infection, injury or surgery; you have an autoimmune or inflammatory condition; you are pregnant; or you take a statin or any other medicine. Keep taking your medicine as prescribed, and talk to your provider before changing it.
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The bottom line
A protein found in pneumonia patients in 1930 now does two jobs. Measured the standard way, it is an alarm that helps doctors judge an infection. Measured with a finer ruler, it is a slow signal of heart risk that can sit quietly for years. The protein is the same. What changes is the question. So when you see either number, ask which question your test was meant to answer, and read the result in that light.
Common questions
Is hs-CRP more accurate than CRP?
It is more sensitive, not more accurate overall. Both measure the same protein. The hs version reads the low levels that matter for heart risk, where it adds about as much as blood pressure or cholesterol. For a big rise, such as a serious infection, a standard CRP test does the job, and doctors use it to guide decisions like antibiotics.
When is hs-CRP ordered?
Mostly to help judge heart attack and stroke risk in people without heart disease. A 2016 review said it fits best when a doctor and patient are unsure about starting a statin. The American College of Cardiology's 2025 statement backs wider use. The U.S. Preventive Services Task Force said in 2018 that the evidence was not enough to say.
What is the normal range for hs-CRP vs CRP?
For hs-CRP, the heart-risk bands are under 1 mg/L (lower risk), 1 to 3 (average) and over 3 (higher). Standard CRP results are read against the reference range printed on your lab report. We did not find one agreed cutoff in the research we read, so go by your report and your provider.
Does a high hs-CRP mean I have heart disease?
No. It is linked to a higher chance of heart disease later, not a diagnosis. Higher CRP is also linked to stroke and to death from some cancers and lung disease, and scientists say the reason for such a wide reach is unclear. Readings also shift over time, so one high number is a reason to talk, not to worry.
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How this article was made
Researched and written from 10 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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- ReviewC-reactive protein - My perspective on its first half century, 1930-1982.Kushner I Front Immunol, 2023.PubMedFull paper
- ReviewA Test in Context: High-Sensitivity C-Reactive Protein.Ridker PM J Am Coll Cardiol, 2016.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
- Randomized trialInflammation, Cholesterol, Lipoprotein(a), and 30-Year Cardiovascular Outcomes in Women.Ridker PM, Moorthy MV, Cook NR et al. N Engl J Med, 2024.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
- 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
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- ReviewErythrocyte Sedimentation Rate and C-reactive Protein Measurements and Their Relevance in Clinical Medicine.Bray C, Bell LN, Liang H et al. WMJ, 2016.PubMed
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