Monitoring Fluid Volume for Patients with Renal Disease. A method includes monitoring an indicator of fluid volume of a patient via a sensor device, and setting an initial fluid volume removal prescription for a blood fluid removal session based on the monitored indicator of fluid volume. The method may further include transmitting data regarding the indicator of fluid volume from the implantable sensor device to fluid removal device. In some embodiments, the fluid removal device sets or calculated the initial fluid volume removal prescription based on the data received from the implantable sensor. The indicator of fluid volume may be an indicator of tissue fluid volume or an indicator of blood fluid volume.