How fluid affects your weight and BMI calculations
Why fluid retention can mask fat loss and how we adjust for oedema in clinical monitoring.
Written by Professor Mohammed Mahdi Althaf
Overview
In chronic kidney disease (CKD), the scales don't always tell the whole truth. Fluid retention (oedema) can significantly inflate your weight, making BMI calculations less accurate.
Fluid vs. Fat
Fluid can accumulate quickly in the legs, abdomen, or lungs. A gain of 2kg in two days is almost certainly fluid, not fat. Conversely, if you are losing fat while gaining fluid, your weight might stay the same on the scales, even though your health is improving.
Clinical Guidance
We use "oedema-free weight" where possible to calculate your dosage and targets. It is essential to report any new swelling or sudden weight changes to your care team.
References
NICE Guideline NG203: Chronic kidney disease: assessment and management.