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Furosemide is a type of medicine called a diuretic.

Diuretics are sometimes called water pills or water tablets because they make you wee more.

Furosemide is only available on prescription. It comes as tablets and as a liquid that you swallow. You can also get it by injection. But this is usually only done in hospital.

Furosemide sometimes comes mixed with other diuretics or potassium.

Uses of furosemide

Furosemide is used to treat high blood pressure and oedema (a build-up of fluid in the body).

It's also sometimes used to help you pee when your kidneys aren't working properly.

Get emergency help

You might have to get emergency help if you:

  • get serious side effects
  • have a serious allergic reaction
  • take too much furosemide

Serious allergic reaction

A serious allergic reaction (anaphylaxis) to furosemide is rare. But you may need to go to an emergency department (ED) if you experience a reaction.

Emergency action required: Call 999 or 112 or go to an ED straight away if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue, eyelids or throat start swelling
  • you have a high temperature (38 degrees Celsius or higher)
  • you feel faint
  • you have blood in your pee or you are peeing less often, sometimes along with a high temperature, drowsiness drowsy swelling of your ankles - these may be signs of swollen kidneys

If you take too much

Emergency action required: Go to your nearest ED straight away or phone your GP if you:

  • take more than your recommended dose of furosemide

Take the furosemide packet or leaflet with you, as well as any remaining medicine with you.

Too much furosemide can cause you to:

  • have a headache
  • feel dizzy, confused or light headed
  • be unable to focus
  • feel weak or have cramps
  • develop blood clots
  • have a pounding or irregular heartbeat
  • faint 

You may also wee more than normal, feel thirsty or feel no interest in anything.

Serious side effects

Urgent advice: Tell your GP straight away if you get:

  • unexplained bruising or bleeding, fever, sore throat and mouth ulcers
  • severe tummy pain which could reach through to your back
  • severe pain in your side or blood in your pee
  • ringing in your ears (tinnitus) or loss of hearing
  • sensitivity to touch or sunlight
  • spasms, muscle twitching or cramps
  • yellowing of your skin or eyes
  • pain when you pee, blood in your pee, dark urine or you find it hard to pee
  • forgetfulness, fits, mood changes and passing out
  • skin rashes
  • headaches or confusion
  • muscle or joint pains
  • dizziness, light-headedness and fainting

When you start taking furosemide

Furosemide starts to work within 1 hour but it may take a few weeks to fully take effect.

The main side effect of furosemide is weeing more often than normal. 

You may not have any symptoms if you're taking furosemide for high blood pressure. In this case, you may not feel any different when you take furosemide. This doesn't mean that the medicine is not working. 

Do not take furosemide in the evening time or you may need to go to the toilet during the night.

A dose of furosemide works for about 6 hours.

You should avoid drinking alcohol while taking furosemide as it may lower your blood pressure further.

Driving and using machines

You may feel drowsy, dizzy or have blurred vision after taking furosemide. Do not drive or operate machinery if you experience these side effects.

Check if you can take furosemide

Most adults and children can take furosemide.

Check with your GP before starting to take furosemide.

You should particularly talk to your GP if you:

  • already have a medical condition
  • have had an allergic reaction to medicine in the past
  • are dehydrated or have lost a lot of blood
  • are trying to get pregnant, already pregnant or breastfeeding
  • have an intolerance to, or you cannot absorb, some sugars such as lactose (in milk) or maltitol (in corn syrup)


Furosemide should not be used during pregnancy as it can pass to your baby.

Talk to your GP straight away if:

  • you become pregnant while taking furosemide

They will need to check the growth of your baby.

If you are pregnant, your GP will only give you furosemide if they think it is absolutely necessary.

If you are pregnant, think you may be pregnant or are planning to have a baby, talk to your GP or pharmacist before taking furosemide.


Do not take furosemide if you are breastfeeding.

The medicine can pass into breast milk.

How and when to take furosemide

Always take furosemide exactly as your GP has told you. Check with your doctor or pharmacist if you are not sure. You should not adjust the dose unless your GP tells you to.

It's usual to take furosemide once a day in the morning. Some people take it twice a day - once in the morning and again at lunchtime.

You can occasionally take furosemide at a different time of day if it's more convenient for you. For example if you need to go out for a few hours in the morning and you will not be near a toilet. Ask your GP or pharmacist to help you plan the best time for you.

You do not need to take furosemide with food. 

If you’re taking it as a liquid, do not use a kitchen teaspoon to measure it as you will not get the right amount. The medicine will come with a plastic syringe or spoon to help you measure the right dose. If you do not have one, ask a pharmacist for one. 

Eating and drinking

Drink normally while you're taking furosemide. Passing pale, clear wee is a sign that you're drinking enough.

Do not eat foods that have a lot of salt in them, such as processed foods or ready-meals. Do not add extra salt when you're cooking or at the table.

Do not buy salt substitutes instead of ordinary table salt. They contain a lot of potassium. This can interfere with certain medicines or cause side effects.

Drinking alcohol

Avoid drinking alcohol while taking furosemide.

It may lower your blood pressure and make you feel dizzy.

If you forget to take it

Do not take a double dose to make up for a forgotten dose.

Take your forgotten dose as soon as you remember. If it's evening time, leave out the missed dose and take your next dose at the usual time. 

Side effects of furosemide

Not everyone gets side effects. If you do get them they often get better as your body gets used to the medicine.

Common side effects

Common side effects include:

  • peeing more than normal, most people need to pee a couple of times within a few hours of taking furosemide
  • feeling thirsty with a dry mouth
  • headaches
  • feeling confused, light-headed or dizzy
  • fainting
  • muscle or joint pains, cramps, spasms or weak muscles
  • feeling or being sick (nausea or vomiting)
  • a fast or irregular heartbeat

Read the patient information leaflet that came with your medicine for a full list of possible side effects.

Non-urgent advice: Find your patient information leaflet

Your patient information leaflet is the leaflet that comes with your medicine. You can find a digital version of the leaflet online.

Report side effects

You can report any suspected side effects to the the Health Products Regulatory Authority (HPRA): report an issue -

Taking furosemide with other medicines

If you’re taking any other medicines or supplements, talk to your GP or pharmacist before you start taking furosemide.

Some medicines interfere with the way furosemide works.

Medicines you buy from a pharmacy or supermarket

Speak to a pharmacist or your GP before taking the following with furosemide: 

  • soluble paracetamol
  • soluble co-codamol
  • remedies for heartburn and indigestion

They may contain a lot of sodium, which is found in salt. Too much salt can stop furosemide working properly.

Read the patient information leaflet that came with your medicine for a full list of medicines that may interfere with furosemide.

Fact check

This content was fact checked by a pharmacist, a GP, the National Medication Safety Programme (Safermeds) and the Health Products Regulatory Authority (HPRA).

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

Page last reviewed: 24 September 2021
Next review due: 24 September 2024