Glycoforms are types of proteins (isoforms) with specific type of glycoprotein attached to them by either posttranslational or cotranslational modifications. In other words, two proteins would be of the same glycoform if they carried the same glycoprotein.

According to Glycoforum, "Glycoform is defined as a subunit of molecules with identical polypeptide sequences but with different glycans present at the sites of glycosylation. It is very important to analyze the glycoform, because different glycoforms of the same glycoprotein have different biological properties. It has been estimated, for example, that recombinant tissue plasminogen activator (rtPA) may contain as many as 11,500 different glycoforms.

"Ion-exchange chromatography, reversed phase HPLC, and a variety of electrophoretic methods are used to separate the glycoforms. In these cases, the separation, which is negatively charged at neutral pH values, is attributed to the hydrophobicity of the samples, and the different degrees of sialic acids. In general, it is quite difficult to analyze the the glycoform populations of the glycoprotein directly, even when careful selection of the conditions can be made. Therefore, it is common practice to first release carbohydrates by chemical or enzymatic methods before analyzing them. The characterization methods of carbohydrates released from glycoproteins used so far are as follows."

Glycoforms are glycoprotein variants described and discovered by microarray studies and cDNA libraries.