The present invention relates to an insoluble composition comprising an acylated 
protein selected from the group consisting of acylated 
insulin, acylated 
insulin analogs and acylated 
proinsulin and preparations thereof.  The formulations are suitable for parenteral or other delivery to a patient for prolonged control of blood glucose levels.  More specifically, the present invention relates to compositions comprising an acylated 
protein complexed with 
zinc, 
protamine and a phenolic compound such that the resulting microcrystals resemble the neutral 
protamine zinc (NPH) 
insulin crystalline form.  Surprisingly; this acylated 
protein composition has been found to have therapeutically superior subcutaneous release 
pharmacokinetics, and longer and flatter glucose 
kinetics than currently marketed NPH insulin formulations.  Furthermore, the crystals of the present invention retain some of the advantageous properties of NPH crystals, namely being able to be easily resuspended and also mixed with soluble insulin.