Furosemide
Furosemide is a potent loop diuretic used clinically for oedema and heart failure. In the PED and physique world it is used — dangerously — for rapid water loss before contests or weigh-ins. Its efficacy is well established, but so are its risks: it causes brisk electrolyte and fluid loss that has produced hospitalisations and deaths among bodybuilders, and it is banned in sport as a masking agent.
01 Overview
Furosemide inhibits the sodium-potassium-chloride co-transporter in the thick ascending limb of the loop of Henle, producing rapid, high-volume diuresis. Onset is fast and the effect large, which is exactly why it is abused for last-minute 'drying out' before bodybuilding shows.
That same potency is the danger. Aggressive diuresis strips potassium, sodium and magnesium, causing cramps, dizziness, arrhythmia and, in severe cases, cardiovascular collapse — a repeatedly documented cause of on-stage collapse and death in the sport. It is also a WADA-prohibited masking agent because it dilutes urine. Any use for physique purposes carries meaningful risk and should be regarded as one of the more hazardous practices in the field.
02 Mechanism
Inhibits the Na-K-2Cl co-transporter in the ascending loop of Henle, blocking sodium and chloride reabsorption and producing rapid, high-volume diuresis with substantial electrolyte loss.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Physique water-cutting (hazardous) | 20–40 mg | Oral | Contest-prep misuse; high risk of dangerous electrolyte disturbance. |
| Oedema (label) | 20–80 mg | Oral | Clinical dosing, titrated; may be repeated. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Rapid diuresis / water lossFast, high-volume fluid loss; the property exploited for physique drying and weight cutting. | large, rapid | Clinical | |
| Blood-pressure reductionLowers blood pressure via volume reduction in fluid-overloaded states. | moderate | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Electrolyte depletionLoss of potassium, sodium and magnesium causing cramps, arrhythmia and, in extreme cases, cardiac collapse — documented in bodybuilder deaths. | Life-threatening | Very common with aggressive use | Clinical | |
| Dehydration / hypotensionVolume depletion causing dizziness, fainting and kidney strain. | Severe | Common with aggressive use | Clinical |