In dialysis for kidney failure patients, the dialysing fluid is iso-osmotic to

In the process of hemodialysis, the dialysing fluid (dialysate) is formulated to be iso-osmotic to blood (specifically blood plasma). This ensures that the osmotic pressure of the fluid matches that of the patient's blood.

• Purpose: Maintaining an iso-osmotic state prevents the net movement of water into or out of the red blood cells, which would otherwise cause them to burst or shrink.
• Mechanism: The dialysing fluid contains the same concentration of electrolytes and glucose as normal plasma but is devoid of nitrogenous wastes like urea.
• Diffusion: Due to the concentration gradient, toxic waste products move from the blood, through a semi-permeable membrane, into the dialysing fluid to be cleared from the body.

According to NCERT, the dialysing fluid has the same osmotic pressure as blood, making option A the most precise answer.