gives non-Newtonian characteristics to blood (i.e. Fahraeus-Lindqvist effect)

adds little to the osmotic pressure of the plasma

prevents loss of the respiratory pigment from the body via the kidneys, seepage into the lymphatics, intercellular space, etc.

allows use of a Hb of relatively small m.w. and size. Provides high oxygen carrying capacity.

provides enhanced control of oxygen affinity (e.g. 2,3 - DPG) (i.e. Hb in solu., would need much higher B.P. to maintain equilibrium