Erythrocyte sedimentation rate

How far red cells settle in a tube in an hour. Inflammatory proteins make them clump and fall faster.

It is a slow inflammation marker, and reading it against CRP tells you roughly how long something has been going on.

It lags CRP by days at both ends -- rising later and taking weeks to come back down -- so a raised ESR with a normal CRP usually means an episode that has already passed. It rises with age, in pregnancy and with anemia, none of which is inflammation.

Worth discussing a raised value that persists once you are well again.