Carrageenan is a family of naturally occurring high molecular weight polysaccharides extracted from red seaweed which yield kappa, iota and lambda types. They differ in properties mainly due to the number and position of ester sulfate groups on the galactose units. While kappa forms a brittle gel, iota forms an elastic gel and lambda does not form a gel. All carrageenans display protein and polyol reactivity.

Based on their properties, they are used as stabilizers, thickeners, suspending agents, gelling agents and flow regulators in pharmaceutical dosage forms.