Furosemide

1. About furosemide

Furosemide is a type of medicine called a diuretic. It's used to treat high blood pressure, heart failure 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.

Diuretics are sometimes called 'water pills' because they make you pee more.

Furosemide is only available on prescription. It comes as tablets and as a liquid that you swallow. It can also be given by injection, but this is usually only done in hospital.

Furosemide sometimes comes mixed with other diuretics or potassium.

2. Key facts

  • 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.
  • Furosemide doesn't usually upset your tummy. You can take it whether or not you've eaten a meal or snack recently.
  • The main side effect of furosemide is peeing more often than normal. Most people need to pee about 30 minutes after taking furosemide, and again within a few hours.
  • Don't take furosemide after 4pm or you may have to wake in the night to go to the toilet.
  • Furosemide is also called by the brand names Frusol and Lasix.

3. Who can and can't take furosemide

Furosemide can be taken by most adults and children, including babies.

However, furosemide isn't suitable for everyone. To make sure furosemide is safe for you, tell your doctor if you have:

  • had an allergic reaction to furosemide or any other medicine in the past
  • low blood pressure
  • symptoms of dehydration, such as being thirsty, having a dry mouth and dark pee
  • liver disease
  • diabetes
  • difficulty peeing
  • a disorder of your adrenal glands called Addison's disease
  • gout
  • an intolerance to, or you cannot absorb, some sugars such as lactose (in milk) or maltitol (in corn syrup)

Tell your doctor that you are taking furosemide if you're going to have:

  • a glucose test
  • a test (such as an X-ray or scan) that involves a dye containing iodine being injected into your blood
  • a major operation or a general anaesthetic to put you to sleep

4. How and when to take it

When will I take it?

It's usual to take furosemide once a day in the morning.

Sometimes you take it twice a day – once in the morning and again at lunchtime. Occasionally, you take it every other day.

You don't need to take furosemide at the same time every day. You can occasionally take it at a different time if it's more convenient for you, for example if you need to go out for a few hours in the morning and you won't be near a toilet.

But don't take furosemide too late in the day (after 4pm) or at night, otherwise you may have to wake up to go to the toilet. Your doctor or pharmacist will tell you the best times for you to take your medicine.

How much will I take?

Doses are usually lower for people over 65 years as they may be more prone to side effects.

For babies and children, your doctor will use your child's weight or age to work out the right dose.

How to take it

Furosemide doesn't usually upset your tummy so you can take it whether or not you've eaten recently.

Swallow the tablets whole with a drink of water.

If you're taking furosemide as a liquid, it will come with a plastic spoon or syringe to help you measure out the correct dose. If you don't have one, ask your pharmacist for one. Do not measure the liquid with a kitchen teaspoon as it won't give the right amount.

Some people take furosemide mixed with other diuretics or potassium:

  • with amiloride (also called co-amilofruse, Frumil or Frumil LS)
  • with spironolactone (also called Lasilactone)
  • with triamterene (also called Frusene)
  • with potassium (also called Diumide-K Continus)

What if I forget to take it?

Take your forgotten dose as soon as you remember, unless it is after 4pm in the afternoon. In this case, leave out the missed dose and take your next dose at the usual time. Do not take a double dose to make up for a forgotten dose.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicines.

What if I take too much?

Too much furosemide can cause headaches, dizziness, a pounding or irregular heartbeat and fainting. You may also pee more than normal and feel thirsty.

The amount of furosemide that can lead to an overdose varies from person to person.

Call your doctor or go to A&E straight away if you take too much furosemide and:

  • feel unwell
  • are over 65
  • have kidney, liver or heart failure

Contact your doctor or go to your nearest hospital accident and emergency (A&E) department straight away, even if you don't have any symptoms.

If you have to go to hospital take the furosemide packet, or the leaflet inside it, plus any remaining medicine with you.

5. Side effects

Like all medicines, furosemide can cause side effects although not everyone gets them.

Side effects often get better as your body gets used to the medicine.

Common side effects

Common side effects of furosemide happen in more than 1 in 100 people. They include:

  • peeing more than normal – most people need to pee a couple of times within a few hours of taking furosemide. You may also lose a bit of weight as your body loses water
  • feeling thirsty with a dry mouth
  • headaches
  • feeling confused or dizzy
  • muscle cramps, or weak muscles
  • feeling or being sick (nausea or vomiting)
  • a fast or irregular heartbeat

Serious side effects

Some people have serious side effects after taking furosemide.

Tell your doctor straight away if you get:

  • unexplained bruising or bleeding, fever, sore throat and mouth ulcers – these could be signs of a blood disorder
  • severe tummy pain which could reach through to your back – this could be a sign of an inflamed pancreas (pancreatitis)
  • severe pain in your side or blood in your urine – these could be signs of inflamed kidneys
  • tinnitus (ringing in your ears) or loss of hearing

Serious allergic reaction

It's possible to have a serious allergic reaction (anaphylaxis) to furosemide.

Contact a doctor 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 or throat start swelling

These are warning signs of a serious allergic reaction. A serious allergic reaction is an emergency.

These are not all the side effects of furosemide. For a full list see the leaflet inside your medicines packet.

Information:

You can report any suspected side effects to the UK safety scheme.

6. How to cope with side effects

What to do about:

  • peeing more than normal – this will last for about 6 hours after taking furosemide. It's nothing to worry about, but if it's inconvenient for you, change the time you take furosemide to one that suits you better (provided it's no later than 4pm). If peeing a lot is still a problem for you, talk to your doctor or pharmacist.
  • feeling thirsty – it's important not to get dehydrated, but how much you drink will depend on why you're taking furosemide. Check with your doctor how much liquid you can drink while you're taking this medicine.
  • dry mouth – chew sugar-free gum or suck sugar-free sweets.
  • headaches – make sure you rest and drink plenty of fluids. Don't drink too much alcohol. Ask your pharmacist to recommend a painkiller. Talk to your doctor if the headaches last longer than a week or are severe.
  • feeling confused or dizzy – if furosemide makes you feel dizzy when you stand up, try getting up very slowly or stay sitting down until you feel better. If you begin to feel dizzy, lie down so that you don't faint, then sit until you feel better. Don't drive or use tools or machines while you're feeling dizzy or shaky.
  • muscle cramps or weak muscles – if you get unusual muscle pain or weakness which isn't from exercise or hard work, talk to your doctor. You may need a blood test to check what might be causing it.
  • feeling or being sick (nausea or vomiting) – take furosemide with or just after a meal or snack. It may help if you stick to simple meals and don't eat rich or spicy food. This side effect usually wears off after a few days. Talk to your doctor about taking an anti-sickness medicine if it carries on for longer.

7. Pregnancy and breastfeeding

Furosemide is not normally recommended in pregnancy or when breastfeeding. However, your doctor may prescribe it if they think the benefits of the medicine outweigh the risks.

If you're trying to get pregnant or you're already pregnant, talk to your doctor about the benefits and possible harms of taking furosemide. These will depend on how many weeks pregnant you are and the reason you need to take it. There may be other treatments that are safer for you.

Furosemide and breastfeeding

Small amounts of furosemide may get into breast milk. It's also possible that furosemide may reduce the amount of milk you produce.

If you need to take furosemide while you're breastfeeding, your doctor and midwife will monitor your baby's weight.

Talk to your doctor, as other medicines might be better while you're breastfeeding.

Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

8. Cautions with other medicines

Some medicines interfere with furosemide to stop it working properly or increase the chances of you having side effects.

Tell your doctor if you're taking:

  • medicines to treat – or which have the side effect of – an irregular heartbeat, including amiodarone, digoxin, disopyramide, flecainide and sotalol
  • medicines that can change the level of potassium in your blood, such as potassium supplements, steroids, or other diuretics
  • medicines used to treat mental health problems, such as amisulpride, lithium, pimozide and risperidone
  • painkillers known as non-steroidal anti-inflammatory drugs (NSAIDs), including diclofenac, ibuprofen and naproxen
  • medicines that treat high blood pressure, or those that have a side effect of low blood pressure
  • a medicine used to treat ulcers called sucralfate. Leave about 2 hours between the time you take furosemide and sucralfate.

Mixing furosemide with medicines that you buy from a pharmacy or supermarket

Some painkillers and remedies that you can buy from a pharmacy or supermarket contain a lot of sodium, which is found in salt. Too much salt can stop furosemide working properly.

Medicines that contain a lot of salt include soluble paracetamol and soluble co-codamol, and remedies for heartburn and indigestion like Gaviscon.

Speak to a pharmacist or doctor to see if these medicines are safe for you to take alongside furosemide.

Mixing furosemide with herbal remedies and supplements

There's very little information about taking herbal remedies and supplements with furosemide.

Important

Tell your pharmacist or doctor if you're taking any other medicines, including herbal remedies, vitamins or supplements.

9. Common questions

How does furosemide work?

Furosemide is a type of medicine called a loop diuretic.

A diuretic makes your body get rid of extra fluid through your kidneys. A loop diuretic works on a specific part of the kidney called the 'loop of Henle' to increase the salt and water you pee out.

This means you have less fluid in your tissues which helps get rid of oedema (swelling). You will also have less fluid in your blood, which helps reduce blood pressure.

How long does furosemide take to work?

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

If you're taking furosemide for high blood pressure, you may not have any symptoms. In this case, you may not feel any different when you take furosemide. This doesn't mean that the medicine isn't working. It's important to keep taking it.

How long does it work for?

A dose of furosemide works for about 6 hours.

How long will I take it for?

Depending on the reason why you're on furosemide, you may have to take it for a long time, even for the rest of your life.

Is it safe to take for a long time?

Furosemide is safe to take for a long time, but you will have to see your doctor or nurse every so often for blood and urine tests. These make sure the chemicals in your blood are properly balanced.

How often you need to see your doctor or nurse for these tests will depend on the reason why you're taking furosemide, if your dose has changed recently, or if you have any other health problems.

Can I come off furosemide now my blood pressure is lower?

Even if furosemide brings down your blood pressure successfully, it's best to carry on taking it. If you stop taking it, your blood pressure could go back up again.

If you need medicines to lower your blood pressure, you'll probably need them for the rest of your life.

Remember, by keeping your blood pressure low, you're protecting yourself against having a heart attack or stroke in the future.

What will happen if I come off it?

Talk to your doctor if you want to stop taking furosemide.

Stopping it may cause your blood pressure to rise – and this may increase your risk of heart attack and stroke.

If you're bothered by side effects, your doctor may be able to prescribe you a different medicine.

Can I drink alcohol with it?

It's best not to drink alcohol while you're taking furosemide. It may lower your blood pressure too much.

Are there similar medicines to furosemide?

There are other diuretics that work in a similar way to furosemide.

There are 3 different types of diuretic: loop diuretics (such as furosemide), thiazide diuretics and potassium-sparing diuretics. Each type of diuretic works on a different part of the kidney.

  • Like furosemide, bumetanide and torasemide are loop diuretics that can be used to treat heart failure. Torasemide can also be used to treat high blood pressure.
  • Thiazide diuretics, such as bendroflumethiazide and indapamide, are used in low doses to treat high blood pressure, and in higher doses to treat heart failure.
  • Potassium-sparing diuretics, such as spironolactone and eplerenone, can be used to treat heart failure. These can also be used if you lose too much potassium with other diuretics.
How much fluid should I drink while I'm taking furosemide?

It's usually best to drink normally while you're taking furosemide. A good rule is to drink enough fluid so that you're not thirsty for long periods. And to steadily increase your fluid intake when exercising and during hot weather. Passing clear pee is a good sign that you're drinking enough.

However, if you have heart failure or kidney problems you might need to limit how much fluid you drink. Your doctor or nurse will tell you exactly how much you need to drink each day.

Is it safe to take furosemide when I'm ill?

If you're ill with a fever (a high temperature above 38C), sweats and shaking, vomiting or diarrhoea, it's best to stop taking furosemide for 1 to 2 days. You can start to take it again when you're eating and drinking normally. If you take furosemide when you have an illness that can make you dehydrated, it can make the dehydration worse.

If you're ill for more than 2 days, contact your doctor.

Can I take furosemide to lose weight?

If you're taking furosemide for high blood pressure or oedema (a build up of fluid), you may lose a bit of weight as your body loses water. But don't take furosemide specifically to lose weight.

Only take furosemide if it's been prescribed, and only for the reason your doctor has prescribed it for you.

Can I take furosemide before surgery?

Tell your doctor that you're taking furosemide if you're going to be put to sleep with a general anaesthetic for an operation or you're going to have a major operation – such as a Caesarean section – without a general anaesthetic.

Furosemide can reduce your blood pressure when it's used with a general anaesthetic.

Your doctor may advise you to stop taking furosemide 24 hours before surgery.

Is there any food or drink I need to avoid?

If you're taking a diuretic such as furosemide, it's important not to have too much salt in your food because this can stop it working.

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

Also, don't buy salt substitutes instead of ordinary table salt, as they contain a lot of potassium, which can interfere with certain medicines or cause side effects.

Adults generally are advised to eat no more than 6 grams of salt a day. Your doctor will tell you if you need to eat even less than this.

Will it affect my contraception?

Furosemide won't affect any type of contraception.

However, some types of hormonal contraception, like the combined contraceptive pill and contraceptive patch, aren't usually recommended for women taking furosemide. This is because some hormonal contraceptives can raise your blood pressure and stop the medicine working properly.

Talk to your doctor if you're taking hormonal contraceptives.

Will it affect my fertility?

There's no evidence that furosemide reduces fertility in men or women. However, if you're a woman and you're trying to get pregnant, talk to your doctor first as this medicine is usually not recommended in pregnancy.

Can lifestyle changes help?

You can boost your general health – plus the health of your heart – by making some key lifestyle changes. These will also help if you have high blood pressure or heart failure.

  • Stop smoking –smoking increases your heart rate and blood pressure. Quitting smoking brings down your blood pressure and relieves heart failure symptoms. Try to avoid secondhand smoke too.
  • Drink alcohol sensibly – drinking too much alcohol raises blood pressure over time and also makes heart failure worse. Men and women shouldn't drink more than 14 units of alcohol a week.
  • Be more active – regular exercise lowers blood pressure by keeping your heart and blood vessels in good condition. It doesn't need to be too energetic – walking every day can help.
  • Eat healthily – aim to eat a diet that includes plenty of fruit and veg, wholegrains, fat-free or low-fat dairy products and lean proteins. It's a good idea to cut down on salt too. Eating too much salt is the biggest cause of high blood pressure – the more salt you eat, the higher your blood pressure will be. Aim for no more than 6g of salt a day.
  • Manage stress – when you're anxious or upset, your heart beats faster, you breathe more heavily and your blood pressure often goes up. This can make heart failure worse too. Find ways to reduce stress in your life. To give your heart a rest, try napping or putting your feet up when possible. Spend time with friends and family to be social and help avoid stress.
  • Vaccinations – if you have heart failure, it's recommended that you have a flu jab every year and a pneumonia vaccination every 5 years. Ask your doctor about these vaccinations. You can have them free on the NHS if you have heart failure.

Page last reviewed: 15/01/2018
Next review due: 15/01/2021