In medicine, protein electrophoresis is a method of analysing the proteins mainly in blood serum.  Before the widespread use of gel electrophoresis, protein electrophoresis was performed as free-flow electrophoresis (on paper) or as immunoelectrophoresis.
Traditionally, two classes of blood proteins are considered: serum albumin and globulin. They are generally equal in proportion, but albumin as a molecule is much smaller and lightly, negatively-charged, leading to an accumulation of albumin on the electrophoretic gel. A small band before albumin represents transthyretin (also named prealbumin). Some forms of medication or body chemicals can cause their own band, but it usually is small. Abnormal bands (spikes) are seen in monoclonal gammopathy of undetermined significance and multiple myeloma, and are useful in the diagnosis of these conditions.
The globulins are classified by their banding pattern (with their main representatives):
* The alpha (α) band consists of two parts, 1 and 2:
** α - α-antitrypsin, α-acid glycoprotein.
** α - haptoglobin, α-macroglobulin, α-antiplasmin, ceruloplasmin.
* The beta (β) band - transferrin, LDL, complement
* The gamma (γ) band - immunoglobulin (IgA, IgD, IgE, IgG and IgM). Paraproteins (in multiple myeloma) usually appear in this band.