Patient-Friendly Explanation

Diuretics, often called water tablets, help the body pass extra salt and water as urine. This can drop the scale by one or two kilograms within days, but that is water, not fat, and it returns as soon as you rehydrate. They are prescribed for heart, kidney and blood-pressure conditions, not for weight loss.

Clinical Definition

Loop and thiazide diuretics produce rapid natriuresis and extracellular fluid loss, transiently lowering body weight without changing fat mass. Misuse for weight loss risks hypokalaemia, hyponatraemia, dehydration, metabolic alkalosis and rebound fluid retention on cessation. Diuretic-driven scale drops can also mask genuine fat loss during a weight-management programme, so trends should be read over weeks rather than days.

Why It Matters

Understanding the difference between water weight and fat loss stops patients from misreading short-term scale changes, and it discourages the dangerous practice of self-prescribing diuretics for slimming.