Furosemide
Also known as: Frusemide, Lasix
What it's for
Furosemide is a strong water tablet (diuretic). It removes extra fluid from your body. It treats heart failure, swollen ankles, and fluid in your lungs. It works quickly.
Comes as: Tablets or liquid
How to take it
- Adults: Usually 20mg to 80mg once a day in the morning.
- Take in the morning to avoid needing the toilet at night.
- Higher doses may be split between morning and lunchtime.
- Take with or without food.
Doses here are typical. Always follow the instructions from your prescriber or on the packet — they come first.
Common side effects
- Needing to pass urine more often (usually settles after a few weeks)
- Feeling thirsty or having a dry mouth
- Feeling dizzy when you stand up
- Headache
The leaflet inside the packet lists all known side effects.
Important safety points
- Can lower potassium, sodium, and magnesium - blood tests may be needed
- Stand up slowly to avoid dizziness
- May raise blood sugar if you have diabetes
- Tell your doctor if you have kidney or liver problems
Get medical help urgently if…
- You pass very little or no urine
- You have severe muscle cramps or weakness
- You have an irregular heartbeat
- You have severe thirst, confusion, or feel very unwell
Call NHS 111 for urgent advice, or 999 if someone is seriously unwell.
Before you act on anything here
This page is general information, written to help you understand — it is not personal medical advice and it cannot tell you what is right for you. Talk to your own GP, pharmacist or nurse about your own health.
- Need help now but it's not an emergency? Call NHS 111 or use 111.nhs.uk.
- Emergency? Call 999 or go to A&E.