What it is used for

Fluid build-up (oedema) caused by heart failure, liver disease or kidney disease
Fluid on the lungs
High blood pressure, occasionally

Read our guides:

Off-label uses

Doctors sometimes prescribe a medicine for a condition it is not officially licensed for. This is called off-label use. It is legal and common when there is good evidence it helps, and your doctor should explain why they are suggesting it.

Furosemide is not commonly used off-label.

How it works

Furosemide acts on part of the kidney called the loop of Henle. It stops salt being reabsorbed, so more salt and water are passed out in your pee. This reduces swelling and breathlessness.

Side effects

Like all medicines, Furosemide can cause side effects, although not everyone gets them. Many are mild and ease after the first few weeks.

Common side effects

needing to pee more often in the hours after a dose
feeling dizzy or light-headed
feeling thirsty
headache
muscle cramps

Tell your doctor or pharmacist if these bother you or do not go away.

Serious side effects

These are rare. Call 111 or contact your doctor straight away if you get:

signs of dehydration, such as confusion, very dark pee, peeing very little or feeling faint
muscle weakness, cramps or an irregular heartbeat, which can be signs of low potassium
ringing in the ears or hearing loss

Call 999 if you have signs of a serious allergic reaction, such as swelling of your lips, mouth, throat or tongue, or trouble breathing.

You can report any side effect to the Yellow Card scheme, run by the medicines regulator.

Stopping and withdrawal

Important safety information

Take it in the morning so you are not up at night to pee.
You need regular blood tests to check your salts and kidneys.
Weigh yourself daily if you have heart failure, and tell your team about sudden weight gain.

Questions about your medicine?

A pharmacist can answer questions about your medicines for free, without an appointment. You can also ask your GP for a medication review. Check if you can get free prescriptions.