Like all medicines, losartan can cause side effects, although not everyone gets them. Side effects often improve as your body gets used to the medicine.
Common side effects
These common side effects of losartan happen in more than 1 in 100 people. There are things you can do to help cope with them:
Feeling dizzy
If losartan 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 if you feel dizzy.
Headaches
Make sure you rest, and drink plenty of fluids. It's best not to drink too much alcohol. Ask your pharmacist to recommend a painkiller.
Headaches should usually go away after the first week of taking losartan. Talk to your doctor if they last longer than a week or are severe.
Feeling sick (nausea)
Try taking your tablets with or after a meal or snack. It may also help if you do not eat rich or spicy food.
Being sick (vomiting)
Stick to simple meals and do not eat rich or spicy food. It might help to take your losartan after you have eaten.
Try drinking small, frequent sips of water to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee.
Do not take any other medicines to treat vomiting without speaking to a pharmacist or doctor.
If you take the combined pill, or progestogen-only pill and you're being sick, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Diarrhoea
Drink plenty of fluids, such as water or squash, to prevent dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee.
If you get severe diarrhoea from a stomach bug or illness, tell your doctor. You may need to stop taking losartan for a while until you feel better. Do not take any medicines to treat diarrhoea without talking to a pharmacist or doctor.
If you take the combined pill, or progestogen-only pill and you have severe diarrhoea, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Pain in your joints or muscles
If you get unusual muscle pain, weakness or tiredness which is not from exercise or physical hard work, talk to your doctor. You may need a blood test to check what might be causing it.
Speak to a doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or lasts more than a few days.
Serious side effects
It happens rarely, but some people have serious side effects after taking losartan.
Call a doctor or call 111 straight away if:
- the whites of your eyes turn yellow, or your skin turns yellow although this may be less obvious on brown or black skin – this can be a sign of liver problems
- you get severe stomach pain – this can be a sign of an inflamed pancreas
- your skin becomes more pale than usual, you feel tired, faint or dizzy, get purple spots (that come from superficial bleeding into the skin), show any sign of bleeding, or have a sore throat and high temperature – these can be signs of a blood or bone marrow disorder
- you feel weak, have an irregular heartbeat, pins and needles and muscle cramps – these can be signs of changes in the potassium levels in your blood
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to losartan.
Immediate action required: Call 999 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
Do not drive yourself to A&E.
The person you speak to at 999 will give you advice about what to do.
Long-term side effects
Sometimes, taking losartan for a long time can cause your kidneys not to work as well as they should. Your doctor will check how well your kidneys are working with regular blood tests.
Other side effects
These are not all the side effects of losartan. For a full list, see the leaflet inside your medicine packet.
Reporting side effects
You can report any suspected side effect using the Yellow Card safety scheme.
Visit the Yellow Card website for more information about reporting side effects.