Some say that too much protein can cause strain on yoru kidneys. I have had diabetic nephropathy for about 4 years nwo, and they have never asked me to cut back.
The way albumen/creatinine was explained to me is as follows:
When your kidneys are damaged from out of control diabetes, the walls of your kidneys transform from being like a t-shirt weave to being like a gauze bandage weave. Healthy kidneys keep albumen (protein) at the right levels, but when the kidneys are damaged, the albumen and can spill through those gaps and the levels will drop. Albumin is a protein in the blood that binds calcium, sodium, potassium, fatty acids and water.
Creatinine is a protein produced by your liver.
If your albumen levels get too low, because your kidneys are spilling the albumen (protein) through into your urine, your liver will create and release creatinine so there is enough protein in yoru blood. A byproduct of producing the extra creatinine is the release of extra LDL cholesterol (the bad one). That is why they check your creatinine levels and cholesterol levels when they are checking kidney function.
I was told that they may restrict protein levels, but I was never told to.