The normal range for a C-reactive protein test is less than 1.0 milligrams per deciliter, which is equivalent to 10 milligrams per liter, according to WebMD. A C-reactive protein value greater than 10 milligrams per liter requires further testing to determine the cause, according to Mayo Clinic.
The underlying cause of elevated C-reactive protein level may be a serious infection, trauma or chronic disease, according to Mayo Clinic. Highly sensitive laboratory values for C-reactive protein levels evaluate the risk of heart disease, according to WebMD. Levels less than 1.0 milligrams per deciliter indicate low risk, values between 1.0 and 3.0 milligrams per deciliter indicate average risk, and levels over 3.0 milligrams per deciliter indicate high risk of heart disease.