1. An insoluble composition, comprising: a) a protein selected from the group consisting of insulin, insulin analog, and proinsulin; b) a derivatized protein selected from the group consisting of derivatized insulin, derivatized insulin analog, and derivatized proinsulin; c) a complexing compound; d) a hexamer-stabilizing compound; and e) a divalent metal cation. 2. The composition of Claim 1, which is an amorphous precipitate. 3. The composition of Claim 1, which is a microcrystal. 4. The composition of Claim 3, wherein the microcrystal has rod-like morphology. 5. The composition of Claim 3, wherein the microcrystal has irregular morphology. 6. The composition of Claim 1, wherein the complexing compound is protamine, the hexamer-stabilizing compound is a phenolic preservative, and the divalent metal cation is zinc. 6. The composition of Claim 1, wherein the derivatized protein is selected from the group consisting of fatty acid-acylated insulin, fatty acid-acylated insulin analogs, and fatty acid acylated proinsulins. 7. The composition of Claim 1, wherein the derivatized protein is mono-acylated at its Lys-Nepsil amino group. 8. The composition of Claim 7, wherein the complexing compound is protamine, which is present at about 0.15 mg to about 0.5 mg per 3.5 mg of total protein. 9. The composition of Claim 8, wherein the divalent metal cation is zinc, which is present at about 0.3 mole to about 0.7 mole per mole of total protein. 10. The composition of Claim 9, wherein the hexamer-stabilizing compound is a phenolic preservative selected from the group consisting of phenol, m-cresol, o-cresol, p-cresol, chlorocresol, methylparaben, and mixtures thereof, and is present at a ratio of at least 3 moles of phenolic preservative to 6 moles of total protein. 11. The composition of Claim 10, wherein the protein is selected from the group consisting of insulin and insulin analogs. 12. The composition of Claim 11, wherein the protein is insulin. 13. The composition of Claim 12, wherein the derivatized protein is insulin that is mono-acylated at the LysB29-Nepsil-amino group. 14. The composition of Claim 13, wherein the derivatized protein is insulin that is acylated with a straight-chain, saturated fatty acid. 15. The composition of Claim 14, wherein the straight-chain, saturated fatty acid is selected from the group consisting of n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, and n-decanoic acid. 16. The composition of Claim 15, wherein the mole ratio between the protein and the derivatized protein is from about 1:9 to about 9:1. 17. The composition of Claim 16, wherein the straight-chain, saturated fatty acid is selected from the group consisting of n-hexanoic acid, n-octanoic acid, and n-decanoic acid. 18. The composition of Claim 17, wherein the straight-chain, saturated fatty acid is selected from the group consisting of n-octanoic acid and n-decanoic acid. 19. The composition of Claim 18, wherein the straight-chain, saturated fatty acid is n-octanoic acid. 20. The composition of Claim 19, wherein the mole ratio between the protein and the derivatized protein is from about 1:3 to about 3:1. 21. The composition of Claim 17, wherein the mole ratio between the protein and the derivatized protein is from about 1:9 to about 1:1. 22. The composition of Claim 11, wherein the protein is an insulin analog. 23. The composition of Claim 22, wherein the protein is LysB28,ProB29-human insulin analog. 24. The composition of Claim 22, wherein the protein is AspB28-human insulin analog. 25. The composition of Claim 1, wherein the derivatized protein is insulin that is mono-acylated at its LysB29-Nepsil-amino group with a straight-chain, saturated fatty acid. 26. The composition of Claim 25, wherein the straight-chain, saturated fatty acid is selected from the group consisting of n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, and n-decanoic acid. 27. The composition of Claim 26, wherein the derivatized protein is selected from the group consisting of B29-Nepsil-hexanoyl-human insulin, B29-Nepsil-octanoyl-human insulin, and B29-Nepsil-decanoyl-human insulin. 28. The composition of Claim 25, wherein the straight-chain, saturated fatty acid selected from the group consisting of n-dodecanoic acid, n-tetradecanoic acid, and n-hexadecanoic acid. 29. The composition of Claim 1, wherein the derivatized protein is di-acylated at the Lys-Nepsil-amino group and is also acylated at one N-terminal Nalpha-amino group, and wherein the fatty acid is selected from the group consisting of n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, and n-decanoic acid. 30. The composition of Claim 1, wherein the derivatized protein is acylated with a branched-chain, saturated fatty acid. 31. The composition of Claim 30, wherein the derivatized protein is acylated with a branched-chain, saturated fatty acid having from three to ten carbon atoms in its longest branch. 32. The composition of Claim 1, wherein the derivatized protein is an insulin analog that is mono-acylated at its Lys-Nepsil-amino group with a straight-chain, saturated fatty acid. 33. The composition of Claim 32, wherein the fatty acid is selected from the group consisting of n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, and n-decanoic acid. 34. The composition of Claim 32, wherein the derivatized protein is an insulin analog that is mono-acylated at the Nepsil-amino group with a fatty acid selected from the group consisting of n-dodecanoic acid, n-tetradecanoic acid, and n-hexadecanoic acid. 35. The composition of Claim 32, wherein the derivatized protein is selected from the group consisting of fatty acid-acylated animal insulins, fatty acid-acylated monomeric insulin analogs, fatty acid-acylated deletion analogs, and fatty acid-acylated pI-shifted insulin analogs. 36. The composition of Claim 35, wherein the derivatized protein is fatty acid-acylated des(B30)-human insulin analog, fatty acid-acylated LysB28,ProB29-human insulin analog, or fatty acid-acylated AspB28-human insulin analog. 37. The composition of Claim 36, wherein the derivatized protein is fatty acid-acylated des(B30)-human insulin analog. 38. The composition of Claim 37, wherein the derivatized protein is B29-Nepsil-myristoyl-des(B30)-human insulin analog. 39. The composition of Claim 36, wherein the derivatized protein is fatty acid-acylated LysB28,ProB29-human insulin analog. 40. The composition of Claim 39, wherein the derivatized protein is B28-Nepsil-myristoyl-LysB28,ProB29-human insulin analog. 41. The composition of Claim 36, wherein the derivatized protein is fatty acid-acylated AspB28-human insulin analog. 42. The composition of Claim 1, wherein the mole ratio between the protein and the derivatized protein is from about 1:9 to about 9:1. 43. The composition of Claim 42, wherein the ratio is from about 1:3 to about 3:1. 44. The composition of Claim 42, wherein the ratio is from about 1:9 to about 1:1. 45. The composition of Claim 1, wherein the protein is insulin. 46. The composition of Claim 1, wherein the protein is an insulin analog. 47. The composition of Claim 46, wherein the protein is a monomeric insulin analog. 48. A suspension formulation, comprising an insoluble phase and a solution phase, wherein the insoluble phase comprises the insoluble composition of Claim 1, and the solution phase comprises an aqueous solvent. 49. The suspension formulation of Claim 48, wherein the solution phase further comprises a phenolic preservative at a concentration of about 0.5 mg per mL to about 6 mg per mL of solution; a pharmaceutically acceptable buffer, and an isotonicity agent. 50. The suspension formulation of Claim 48, wherein the solution phase further comprises insulin, an insulin analog, a derivatized insulin, or a derivatized insulin analog. 51. The suspension formulation of Claim 50, wherein the solution phase comprises insulin. 52. The suspension formulation of Claim 50, wherein the solution phase comprises derivatized insulin. 53. The suspension formulation of Claim 50, wherein the solution phase comprises an insulin analog. 54. The suspension formulation of Claim 50, wherein the insulin analog is a monomeric insulin analog. 55. The suspension formulation of Claim 50, wherein the insulin analog is LysB28,ProB29-human insulin analog. 56. The suspension formulation of Claim 50, wherein the insulin analog is AspB28-human insulin analog. 57. The suspension formulation of Claim 48, wherein the solution phase further comprises a protein selected from insulin and insulin analogs and a derivatized protein selected from derivatized insulin and derivatized insulin analogs. 58. The suspension formulation of Claim 57 wherein the protein in the solution phase is the same protein that is in the insoluble phase, and wherein the derivatized protein in the solution phase is the same derivatized protein that is in the insoluble phase. 59. The suspension formulation of Claim 48, wherein the insoluble phase consists essentially of an amorphous precipitate. 60. The suspension formulation of Claim 48, wherein the insoluble phase consists essentially of a microcrystal. 61. The suspension formulation of Claim 48, wherein the insoluble phase consists of a mixture of amorphous precipitate and microcrystal. 62. The suspension formulation of Claim 48, wherein the solution phase further comprises zinc and protamine, wherein the ratio of zinc to total protein in the suspension formulation is from about 5 to about 7 mole of zinc atoms per mole of total protein, and the ratio of protamine to total protein in the suspension formulation is from about 0.25 mg to about 0.5 mg per mg of total protein. 63. A method of treating diabetes comprising administering the composition of Claim 1 to a patient in need thereof in a quantity sufficient to regulate blood glucose levels in the patient. 64. A method of treating hyperglycemia comprising administering the composition