C-Reactive Protein (CRP / hs-CRP): Normal Range, High & Low Causes
What CRP / hs-CRP measures
CRP is made by the liver in response to inflammation. A standard CRP test detects significant inflammation or infection, while the high-sensitivity (hs-CRP) version picks up tiny rises that relate to long-term heart risk.
CRP / hs-CRP reference ranges
| Category | Conventional units | SI units |
|---|---|---|
| hs-CRP: lower cardiovascular risk | Below 1 mg/L | Same (mg/L) |
| hs-CRP: average risk | 1 – 3 mg/L | Same (mg/L) |
| hs-CRP: higher risk | Above 3 mg/L | Same (mg/L) |
| Standard CRP: active inflammation likely | Above about 10 mg/L | Same (mg/L) |
Some labs report CRP in mg/dL. Multiply mg/dL by 10 to get mg/L. hs-CRP should be measured when you are well, because infections raise it temporarily.
Common causes of a high result
- Infections (bacterial, and some viral)
- Autoimmune and inflammatory diseases such as rheumatoid arthritis
- Recent injury, surgery or heart attack
- Obesity, smoking and poor sleep (modest long-term rise)
- Periodontal disease
Common causes of a low result
- A low CRP is the goal and is not a concern
How to prepare for the test
No fasting needed. For hs-CRP, avoid testing during an illness and repeat an unexpectedly high result after two weeks.
How often to retest
Repeated while an infection or inflammatory condition is being treated, or as advised.
Track CRP / hs-CRP over time
Upload your reports and Labgist plots every CRP / hs-CRP result on one timeline, converts units and shows what changed.
Get the appFrequently asked questions
What is the difference between CRP and hs-CRP?
Both measure the same protein. hs-CRP is more sensitive at very low levels and is used to estimate long-term heart risk, while standard CRP detects active inflammation.
What is a normal CRP?
Below 3 mg/L is usually normal for standard CRP. Above about 10 mg/L suggests active inflammation or infection.
Can I lower my hs-CRP?
Not smoking, regular exercise, a healthy weight, good sleep and treating gum disease can lower chronic inflammation. Medicines like statins also lower it.
Related tests
Sources
- MedlinePlus: C-Reactive Protein (CRP) Test
- MedlinePlus: Medical tests (U.S. National Library of Medicine)
This page is general education and was last updated 2026-10-30. It is not a substitute for medical advice. See our editorial approach.