Red cell casts appear as clear cylinders containing red blood cells and may have an orange red tinge. Their presence indicates bleeding into the nephron.

Red cells within the cast are rapidly hemolyzed and the cast becomes a hemoglobin cast, having an orange color and a homogeneous ground-glass texture. In order for a cast to be considered an RBC cast, the outline of the red cells must be clearly visible in at least one area of the cast.