The present invention relates to methods and means for reducing the viscosity of a pharmaceutical formulation comprising an antibody or other therapeutic protein at a high concentration. The present invention provides a liquid pharmaceutical formulation comprising an antibody as active ingredient at a concentration of 220 to 400 mg/ml and acetate at a concentration of 20 to 150 mM. The liquid pharmaceutical formulation has reduced viscosity that does not impede processing or injection of the pharmaceutical formulation. Also provided is a container containing the liquid pharmaceutical formulation, a kit containing the container and instructions for use, and method for reducing viscosity of a liquid pharmaceutical formulation comprising a protein or an antibody at a concentration of 220 to 400 mg/ml, the method comprising providing the liquid pharmaceutical formulation, and adding acetate to a final concentration of 20 to 150 mM, wherein the viscosity of the liquid pharmaceutical formulation is reduced as compared to the same liquid pharmaceutical formulation without acetate.
