Which labs typically improve after a successful dialysis session?

• A. Blood Urea Nitrogen and Potassium Only
• B. Creatinine and Phosphate
• C. Blood Urea Nitrogen, Creatinine, and Potassium
• D. Phosphate and Calcium

Answer: (C)

Dialysis works by clearing waste products and rebalancing electrolytes that build up when the kidneys aren’t functioning. The labs that most reliably show improvement right after a session are those that reflect the clearance of small solutes and potassium.

Blood urea nitrogen decreases because urea is a small waste product that dialysis efficiently removes from the blood. Serum creatinine also declines after dialysis since creatinine is cleared by the dialysis membranes, and its level drops as waste is filtered out. Potassium, a key electrolyte that can accumulate and lead to dangerous arrhythmias, is actively removed by dialysis, so its level often falls into a safer range post-treatment.

Phosphate and calcium don’t always show the same immediate, predictable improvement after one dialysis session. Phosphate removal can be variable due to its distribution between body compartments and the influence of dialysate phosphate concentration and binders used between sessions. Calcium levels can be affected by several factors, including dialysate calcium and bone-mineral metabolism, making their short-term changes less consistent.

So the labs that typically improve after a successful dialysis session are BUN, creatinine, and potassium.