IUPAC defines dextrans as "Branched poly-α-d-glucosides of microbial origin having glycosidic bonds predominantly C-1 → C-6".

This characteristic branching distinguishes a dextran from a dextrin, which is a straight chain glucose polymer tethered by α-1,4 or α-1,6 linkages.

[5] Dextran is a complicating contaminant in the refining of sugar because it elevates the viscosity of sucrose solutions and fouls plumbing.

Clots formed after administration of dextrans are more easily lysed due to an altered thrombus structure (more evenly distributed platelets with coarser fibrin[citation needed]).

Outside of these features, larger dextrans, which do not pass out of the vessels, are potent osmotic agents, thus have been used urgently to treat hypovolemia [citation needed].

The larger dextrans (>60,000 Da) are excreted poorly from the kidney, so remain in the blood for as long as weeks until they are metabolized.

[15] The pathogenesis of this kidney failure is the subject of many debates with direct toxic effect on tubules and glomerulus versus intraluminal hyperviscosity being some of the proposed mechanisms.

[citation needed] Patients with history of diabetes mellitus, chronic kidney disease, or vascular disorders are most at risk.