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hs-CRP

C-reactive protein is an inflammatory biomarker and tests for hs-CRP can detect low-grade inflammation which could have negative heart health effects.

Author: Leanne Edermaniger

May 20, 2024

Reviewed by: Dr Thom Phillips

In this article:

What is CRP?

C-reactive protein or CRP is a protein made in the liver which rises in response to inflammation, infection, or trauma. Levels can also increase after a heart attack or may be monitored if you have an inflammatory condition like arthritis[1].

CRP binds to damaged tissue, nuclear antigens present in autoimmune conditions, and some pathogenic organisms. It is thought that CRP acts like a surveillance molecule, signalling when inflammation is present, and activating the body’s adaptive immune system to deal with the source[2].

What’s the difference between CRP and hs-CRP?

During acute infection, CRP levels can rise to as much as 500 mg/L, which makes it easy to detect. However, chronic low-grade inflammation plays an important role in developing diseases such as atherosclerosis, so more sensitive tests are needed to detect this type of inflammation[3]. Therefore, high-sensitivity CRP (hs-CRP) can accurately detect low levels of inflammation and predict your heart disease risk[4].

What is a hs-CRP Blood Test?

A hs-CRP blood test is a biomarker for inflammation. It can give you a good indication of your cardiovascular disease risk and predict the likelihood of heart attacks, stroke, peripheral arterial disease, and sudden cardiac death in healthy people with no history of heart disease[5].

hs-CRP is a good biomarker for inflammation, especially the low-level, long-term type associated with the development of atherosclerosis, which produces very small amounts of C-reactive protein. So, the hs-CRP test is a more sensitive detector of low-grade inflammation which could increase the risk of heart attacks and strokes.

What is a Normal hs-CRP Level?

A healthy hs-CRP level is between 0 and 5 mg/L. At Forth, the average hs-CRP level for our customers is 1.9 mg/L: 2.2 mg/L for women and 1.7 mg/L for men.

Our data also shows that hs-CRP levels appear to increase with age:

Age hs-CRP level (mg/L)
18 – 29 1.6
30 – 39 1.9
40 – 49 1.9
50 – 59 2
60+ 2.3

It’s important to note that CRP itself is not harmful, but a higher level demonstrates a higher-than-normal amount of inflammation in the body.

What Causes a High hs-CRP Level?

An elevated hs-CRP level indicates an increased risk of cardiovascular disease, so it may be measured alongside other biomarkers, including cholesterol and triglycerides, to determine your risk.

Short-term infections can also raise your hs-CRP levels, including:

  • Cold and flu viruses
  • Pneumonia
  • Urinary tract infections (UTIs)
  • Gastrointestinal infections
  • Fungal infections

Chronic inflammatory conditions and autoimmune diseases increase hs-CRP, and the test may be used to diagnose:

  • Rheumatoid arthritis
  • Lupus
  • Chronic obstructive pulmonary disorder (COPD)
  • Inflammatory bowel disease (IBD)
  • Cancer

A sedentary lifestyle can cause a high hs-CRP blood test level, leading to negative health outcomes, including obesity and an increased risk of heart disease[6].

If you have recently experienced an acute illness, such as a cough, or recovered from an injury[7], then a hs-CRP may return a falsely high result.

Overtraining and CRP levels

High CRP levels are a strong indicator of inflammation caused by tissue injuries resulting from overtraining or poor recovery.

A 2019 study found that athletes with a high exercise volume had significantly higher CRP levels than non-athletes. So, there is some evidence that high levels of physical activity can increase inflammatory biomarkers [12].

Although research shows that regular exercise with adequate recovery periods can lead to a long-term reduction in circulating CRP levels, overtraining can have the opposite effect[13]. Therefore, it is vital to build sufficient recovery and rest periods into your training schedule.

Is too high a hs-CRP level dangerous?

The consensus is that a hs-CRP level above 3 mg/L is a high risk for cardiovascular disease. There are links between inflammatory conditions, including gum disease and arthritis, and vascular disease risk. Therefore, suggesting that all types and causes of inflammation could negatively affect blood vessel walls, and increase the risk of developing atherosclerosis.

How to Lower hs-CRP Levels?

CRP levels can fluctuate in the body depending on the cause of inflammation. For example, if they are increased because of a recent infection, then they should naturally return to normal when the source of the infection has been cleared from the body.

If raised hs-CRP levels are believed to be caused by chronic low-grade inflammation, several lifestyle changes can be made to help reduce them.

Quit smoking

Smoking increases the level of inflammation in the body and as a direct result raises CRP levels. A study published in 2022 found that hs-CRP levels significantly reduced in smokers who quit for 17 months and had smoked for less than 20 years[8].

Exercise more

Exercise is hailed as one of the best ways to lower C-reactive protein levels, alongside diet and weight loss. Milani et al., (2004) demonstrated that a cardiac rehabilitation and exercise training programme significantly lowered hs-CRP levels independent of weight loss or statin use in coronary heart disease patients[9]. Further research has shown that circulating hs-CRP levels decrease in response to increased exercise[10].

Weight loss

Obesity is a contributing factor to elevated CRP levels[11], so weight loss can help. In 2007, Selvin and colleagues demonstrated that for each 1 kilogram of body weight lost, CRP levels decreased by 0.13 mg/L. Therefore, the more weight lost, the bigger the reduction in CRP levels, and the lower the risk of developing heart disease or experiencing a cardiac event.

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.

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Article references

  1. Wolska, A. and Remaley, A.T. (2022) ‘CRP and high-sensitivity CRP: “What’s in a name?”’, The Journal of Applied Laboratory Medicine, 7(6), pp. 1255–1258. doi:10.1093/jalm/jfac076.

  2. hs-CRP (2018) Lab Tests Online. Available at: https://labtestsonline.org.uk/tests/hs-crp (Accessed: 25 April 2024).

  3. Bassuk, S. S., Rifai, N., & Ridker, P. M. (2004). High-sensitivity C-reactive protein: clinical importance. Current problems in cardiology, 29(8), 439–493.

  4. Pritchett J. W. (1996). C-reactive protein levels determine the severity of soft-tissue injuries. American journal of orthopedics (Belle Mead, N.J.), 25(11), 759–761.

  5. Milani, R., Lavie, C. and Mehra, M. (2004) ‘Reduction in C-reactive protein through cardiac rehabilitation and exercise training’, Journal of Cardiopulmonary Rehabilitation, 24(4), pp. 281–282. doi:10.1097/00008483-200407000-00014.

  6. Aronson, D. et al. (2004) ‘Obesity is the major determinant of elevated C-reactive protein in subjects with the metabolic syndrome’, International Journal of Obesity, 28(5), pp. 674–679. doi:10.1038/sj.ijo.0802609.

This article was written by Leanne Edermaniger

This information has been medically reviewed by Dr Thom Phillips

Thom works in NHS general practice and has a decade of experience working in both male and female elite sport. He has a background in exercise physiology and has published research into fatigue biomarkers.

Dr Thom Phillips

Dr Thom Phillips

Head of Clinical Services