Albumin is a protein in your blood plasma. In healthy kidneys, the albumin does not pass from the blood in to the urine. There are filters in the kidneys that prevent large molecules, such as albumin, from passing through. This filter is the glomerular membrane.
High blood sugar levels associated with diabetes can damage this membrane over time. If your kidneys are damaged, albumin can be excreted in your urine, instead of filtering through the kidneys.
This condition is called "albuminuria" and is an indicator of kidney disease. Kidney disease is a serious long-term complication of diabetes.

