Blood serum

In blood, the serum (/ˈsɪərəm/ or /ˈsɪrəm/) is the component that is neither a blood cell (serum does not contain white or red blood cells) nor a clotting factor; it is the blood plasma not including the fibrinogens. Serum includes all proteins not used in blood clotting (coagulation) and all the electrolytes, antibodies, antigens, hormones, and any exogenous substances (e.g., drugs and microorganisms).

The study of serum is serology, which may also include proteomics. Serum is used in numerous diagnostic tests, as well as blood typing.

Blood is centrifuged to remove cellular components. Anti-coagulated blood yields plasma containing fibrinogen and clotting factors. Coagulated blood (clotted blood) yields serum without fibrinogen, although some clotting factors remain.

...
Wikipedia