High or Low C-Reactive Protein in Athletes: Causes and What to Do
C-reactive protein, or CRP, is one of the most common inflammation tests ordered in the United States. For athletes, interpreting the result is tricky: hard training can raise it, and very fit people often have strikingly low values. Our editorial team explains what high and low CRP mean for active people and what steps make sense.
What CRP is and how it is measured
CRP is a protein produced by the liver in response to inflammation, mainly under the influence of interleukin-6. Its levels can rise rapidly, within hours, during infections, injuries or inflammatory conditions, and fall again as inflammation resolves.
There are two common tests. Standard CRP is used to detect significant inflammation, such as infection. High-sensitivity CRP (hs-CRP) measures much lower levels and is used to estimate cardiovascular risk.
In the US, results are usually reported in mg/L for hs-CRP and sometimes in mg/dL for standard CRP, so units on your lab report are important to check.
For cardiovascular risk assessment, the American Heart Association and CDC have described hs-CRP categories: under 1 mg/L as lower risk, 1–3 mg/L as average, and above 3 mg/L as higher risk. Values above 10 mg/L usually suggest acute inflammation and should be repeated after recovery.
Why CRP can be high in athletes
Strenuous exercise triggers a temporary inflammatory response, especially after long-distance events or heavy eccentric work. CRP can rise significantly after a marathon or ultramarathon, often peaking about 24–48 hours later.
Other common causes of elevated CRP in active people include:
- Upper respiratory infections and other viral or bacterial infections.
- Injuries such as muscle strains, tendon problems or fractures.
- Overreaching and overtraining, though CRP is not a reliable stand-alone marker for it.
- Dental infections and gum disease.
- Chronic inflammatory conditions such as rheumatoid arthritis or inflammatory bowel disease.
- Excess body fat, poor sleep and smoking.
Because exercise affects CRP, testing shortly after a hard session or race can give a misleading result. Many sports medicine physicians recommend avoiding intense training for at least 48 hours before the test.
Why CRP can be very low
Strictly speaking, there is no clinically meaningful "too low" CRP. Low hs-CRP values, below 1 mg/L, are typically associated with lower cardiovascular risk.
Regular physical activity is associated with lower baseline CRP. Observational studies consistently show lower levels in fitter people, likely reflecting reduced body fat, better insulin sensitivity and anti-inflammatory effects of regular training.
Certain medications can lower CRP, including statins, NSAIDs, corticosteroids and some biologic drugs. If you take these, a low value might reflect treatment rather than baseline health.
In rare cases, people with severe liver disease may produce less CRP, but this is a clinical context, not something typically seen in healthy athletes.
How to interpret your result
A single result should always be interpreted in context: how you felt, recent training, illness and other blood tests.
| hs-CRP (mg/L) | General interpretation | Possible next step |
|---|---|---|
| < 1 | Low cardiovascular risk category | No action needed |
| 1–3 | Average risk category | Review lifestyle, retest if needed |
| 3–10 | Higher risk category or recent stress | Repeat after 2 weeks of rest from hard training |
| > 10 | Likely acute inflammation or infection | Look for cause; see physician |
The CDC and AHA recommend averaging two hs-CRP measurements taken about two weeks apart when using it for cardiovascular risk assessment.
Persistently elevated CRP without an obvious cause, especially with symptoms such as fever, weight loss, joint pain or night sweats, requires medical evaluation.
What to do if CRP is high
First, consider timing. Was the test taken within two days of a hard workout, race or illness? If so, retesting after recovery is the logical next step.
If CRP remains elevated, work with your physician to identify the cause. Basic evaluation might include a complete blood count, kidney and liver tests, and in some cases specific tests for infection or autoimmune disease.
Lifestyle factors with evidence for lowering chronic CRP include reducing excess body fat, improving sleep, not smoking and following a dietary pattern rich in vegetables, fruits, whole grains and fish, such as the Mediterranean diet.
Supplements such as omega-3s or curcumin are sometimes promoted to lower CRP. Some trials show modest reductions, but they should not replace investigation of the underlying cause.
Editorial team conclusions
For athletes, a high CRP result often reflects recent exercise or minor illness, so timing of the test is critical.
Persistently high CRP needs medical evaluation to rule out infection, injury or inflammatory disease. A low CRP is generally a good sign and is common in fit people.
Plan blood tests after at least 48 hours without intense training and interpret results together with your physician.
Related topics on our site: creatine kinase in athletes, ferritin and iron status in endurance sports, and how to prepare for blood tests.
References
- Pearson TA, Mensah GA, Alexander RW, et al. Markers of inflammation and cardiovascular disease: application to clinical and public health practice: a statement for healthcare professionals from the CDC and AHA. Circulation. 2003;107(3):499–511.
- Kasapis C, Thompson PD. The effects of physical activity on serum C-reactive protein and inflammatory markers: a systematic review. J Am Coll Cardiol. 2005;45(10):1563–1569.
- Ridker PM. Clinical application of C-reactive protein for cardiovascular disease detection and prevention. Circulation. 2003;107(3):363–369.
- Pepys MB, Hirschfield GM. C-reactive protein: a critical update. J Clin Invest. 2003;111(12):1805–1812.
- Fallon KE. The acute phase response and exercise: the ultramarathon as prototype exercise. Clin J Sport Med. 2001;11(1):38–43.
- Lee EC, Fragala MS, Kavouras SA, et al. Biomarkers in sports and exercise: tracking health, performance, and recovery in athletes. J Strength Cond Res. 2017;31(10):2920–2937.
- https://farmaciadeportivaes.com/
