Interdialytic weight gain is typically expressed as a percentage of which of the following?

• A. It is a percentage of the patient’s age
• B. It is the percentage of total body weight gained between sessions
• C. It is the percentage of body fat
• D. It is the percentage of lean body mass gained during dialysis

Answer: (B)

Interdialytic weight gain reflects how much fluid a patient accumulates between dialysis sessions. Clinically, it’s expressed as a percentage of the patient’s total body weight so the value is comparable across different body sizes. The amount gained between sessions (in kilograms) is divided by the patient’s current total body weight and multiplied by 100. This helps clinicians assess fluid status and guide fluid restrictions and dialysis planning. It’s not about age, body fat percentage, or lean body mass—the concept specifically tracks fluid gain between treatments.

Example: if a patient gains 2.8 kg between sessions and their total body weight is 70 kg, IDWG as a percent is (2.8 / 70) × 100 = 4%.