Glucose sparing is a central component of modern peritoneal dialysis therapy, necessary to reduce the trade-offs of the therapy in terms of membrane protection and alleviation of systemic consequences. We present a detailed exploration of a metric for this approach in the form of the index of ultrafiltration efficiency, that we propose as a guide for designing therapeutic regimens and for the development of new dialysis solutions. Based on insights from exploration of ultrafiltration efficiency with various dialysis solutions, we propose an approach to optimizing dialysis prescription.