Furosemide is a type of medicine called a diuretic. Diuretics are sometimes called water pills or water tablets. This is because they make you pee more.
Furosemide is only available on prescription.
It comes as:
- tablets
- a liquid that you swallow
- an injection - 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
- oedema (a build-up of fluid in the body)
It's also sometimes used to help you pee when your kidneys are not working properly.
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 peeing more often than normal. Most people need to pee about 30 minutes after taking furosemide, and again within a few hours.
You may have been prescribed furosemide for high blood pressure without having any symptoms of that condition. So you may not feel any different when you take the medicine. This does not mean that the medicine is not working. It's important to keep taking it.
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.
Avoid drinking alcohol while taking furosemide. Drinking alcohol while on the medicine 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
- have an intolerance to, or you cannot absorb, some sugars such as lactose (in milk) or maltitol (in corn syrup)
- are trying to get pregnant, already pregnant or breastfeeding
Pregnancy and furosemide
If you are pregnant, your GP will only give you furosemide if they think it is absolutely necessary.
Non-urgent advice: Talk to your GP or pharmacist if you are:
- pregnant
- think you may be pregnant
- are planning to have a baby
Urgent advice: Talk to your GP straight away if:
- you become pregnant while taking furosemide
Your GP will need to check the growth of your baby.
Do not take if breastfeeding
Do not take furosemide if you are breastfeeding. It can pass into breast milk.
Talk to your GP or pharmacist if you're:
- breastfeeding
- planning to breastfeed
Other medicines might be better while breastfeeding.
Furosemide and fertility
There's no evidence that furosemide reduces fertility in men or women.
But if you're trying to get pregnant, talk to your GP first. They will need to review your medical condition and medicine before you try for a baby.
How and when to take furosemide
Always take furosemide exactly as your GP has told you. Check with your GP 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.
Try not to take furosemide too late in the day or at night. You may have to wake up to go to the toilet. Talk to your GP or pharmacist about the best times for you to take your medicine.
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 pee is a sign that you're drinking enough.
But if you have heart failure or kidney problems you might need to limit how much you drink. Your GP or nurse can tell you how much you need to drink each day.
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.
Avoid 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.
If you take too much
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 pee more than normal, feel thirsty or feel no interest in anything.
Emergency action required: Go to your nearest emergency department (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.
Side effects
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
These are common side effects of furosemide. There are things you can do to help cope with them:
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 (as long as it's not too late in the evening).
If peeing a lot is still a problem for you, talk to your GP 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 fluids - ask your GP how much you can drink while taking this medicine. Avoid alcohol.
Ask your pharmacist to recommend a painkiller. Talk to your GP 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 do not faint, then sit until you feel better.
Do not drive, ride a bike or use tools or machinery while you're feeling dizzy.
Feeling or getting sick
Stick to simple meals if you feel sick (nausea) or you have been getting sick (vomiting). Do not eat rich or spicy food. If you're getting sick, try small frequent sips of water to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee.
If you take contraceptive pills and you're getting sick, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Speak to a GP or pharmacist if any of these side effects bother you or last more than a few days.
Serious side effects
Urgent advice: Tell your GP 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 pee - these could be signs of inflamed kidneys
- 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 - these could be signs of a liver problem
- 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
Serious allergic reaction
A serious allergic reaction (anaphylaxis) to furosemide is rare.
Emergency action required: Call 112 or 999 or go to an emergency department (ED) straight away if:
- you get a skin rash that may is itchy, red, swollen, blistered or peeling
- 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
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 Health Products Regulatory Authority (HPRA): report an issue - hpra.ie
Taking furosemide with other medicines
Some medicines interfere with the way furosemide works.
Non-urgent advice: Talk to your GP or pharmacist:
before starting on furosemide if you're taking:
- any other medicines
- supplements including potassium supplements - these change the levels of potassium in your blood and can affect the way furosemide works
Read the patient information leaflet that came with your medicine for a full list of medicines that may interfere with furosemide.
Medicines you buy without a prescription
If you are taking furosemide, talk to a pharmacist or your GP before taking:
- soluble paracetamol
- soluble co-codamol (paracetamol combined with codeine)
- 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.
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).
