The Full form of CRP is C-Reactive Protein. CRP is a substance that the liver makes in response to inflammation. The C-reactive protein test measures the amount of this protein in the blood. The test can help to diagnose acute and chronic conditions that cause inflammation. CRP is classified as an acute phase reactant, which means that its levels will rise in response to inflammation. Other common acute phase reactants include the ESR (Erythrocyte Sedimentation Rate) and blood platelet count. Many people who have moderate infections or injuries, or conditions that cause chronic inflammation, may experience similar symptoms. These include unexplained exhaustion, pain, muscle stiffness, soreness, and weakness, low-grade fever, chills, a headache, nausea, loss of appetite, and indigestion, difficulty sleeping or insomnia and unexplained weight loss. People with very high CRP levels are most likely to have an acute bacterial infection. The signs of acute infection include high fever, rapid heart rate, uncontrollable sweating, chills, or shaking, uncontrollable or persistent vomiting, retching, or diarrhea, difficulty breathing, rash or hives, parched lips, mouth, and skin, dizziness or lightheadedness, a severe headache, body pain, stiffness, or soreness and loss of consciousness.