Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)

What this test is

ESR and CRP are two blood tests. Both go up when there is swelling or irritation somewhere in the body. CRP reacts faster and is the more useful of the two, so Canadian lab guidance says CRP should be the main test for this. Your doctor may check CRP for a clear reason, such as swollen joints or a fever that won't go away. CRP is also one of a few tests used to help sort out widespread pain and tiredness. ESR is only added in certain cases, such as an older adult with new stiffness in the shoulders or hips. If you feel well and have no signs of swelling or irritation, these tests do not usually help as routine bloodwork.