Losartan

What is losartan?

Losartan is a medicine used to treat several conditions related to the heart and kidneys. It belongs to a group of drugs called angiotensin receptor blockers (ARBs), which help relax blood vessels and reduce blood pressure[1]. 

What is losartan used to treat?

Doctors commonly prescribe losartan for[1]: 

• High blood pressure (hypertension) 

• Heart failure 

• Protecting the kidneys in people with kidney disease or type 2 diabetes 

• Reducing stroke or heart attack risk in people with high blood pressure and left ventricular hypertrophy (enlarged heart) 

Who can take losartan?

Losartan can be taken by most adults and children over 6 years (for high blood pressure only). 

You should make sure your doctor is aware if you[1]: 

• Are pregnant, especially in the second or third trimester 

• Have severe liver, heart, or kidney problems 

• Have diabetes 

• Are on a low salt diet 

• Have low blood pressure 

• Are allergic to losartan  

Please tell your doctor or pharmacist about any conditions you may have or medication you take before you start treatment, and always follow the instructions in the Patient Information Leaflet[2].

What is the usual dose of losartan?

Losartan comes as 12.5mg, 25mg, 50mg and 100mg tablets. The standard dose for adults[1]: 

• Starting dose is usually 50mg once daily for high blood pressure or kidney protection, 12.5mg to 150mg once daily for heart failure, and 25mg once daily for kidney protection in over 75s 

• Dose may be adjusted between 25-100mg depending on response 

For children (6–16 years): 

• Dose is based on weight and condition, prescribed by a specialist 

For elderly patients: 

• May start on a lower dose due to increased sensitivity

How do you take losartan?

Take losartan once a day, with or without food[1]: 

• Swallow tablets whole with water 

• Try to take it at the same time each day 

• Avoid grapefruit juice, which may interfere with how losartan works 

Can you stop taking losartan?

Do not stop losartan suddenly without speaking to your doctor. Stopping can cause your blood pressure to rise again, increasing the risk of complications like stroke or heart attack[1]. 

What to do if you take too much losartan

Taking too much losartan may cause[1]: 

• Dizziness or fainting 

• Slow or fast heartbeat 

Call NHS 111 or go to A&E immediately if you suspect an overdose. Take the medicine packaging with you if possible. 

What if you forget a dose of losartan?

If you forget to take your dose[1]: 

• Take it as soon as you remember 

• If it’s almost time for your next dose, skip the missed one 

• Never take a double dose to make up for a missed tablet 

Medicines you can and can't take with losartan

Tell your doctor about all other medicines you're taking. Some drugs can interact with losartan, including[1]: 

• NSAIDs (e.g. ibuprofen) – may reduce its effectiveness 

• Diuretics (water tablets) – may lower your blood pressure too much 

• Lithium – can increase the risk of side effects 

• Other blood pressure medications – may increase the risk of low blood pressure 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2].

What are the side effects of losartan?

Common side effects (up to 1 in 10 people) include[1]: 

• Dizziness or light-headedness 

• Headache 

• Tiredness 

• Low blood pressure 

Uncommon or rare side effects include[1]: 

• Kidney problems 

• High potassium levels (may cause muscle cramps or irregular heartbeat) 

• Allergic reactions – including rash, swelling of the face or throat, and difficulty breathing 

You should contact your GP if you experience any of these symptoms. In rare cases, the medicine may cause a serious allergic reaction (anaphylaxis). You should call 999 or visit A&E immediately if you believe this is happening[1]. 

Symptoms of anaphylaxis include:  

• Difficulty breathing  

• Tightness in throat and chest  

• Swelling of the tongue or throat  

• Feeling faint or dizzy  

• Blue/grey skin or lips  

• Loss of consciousness

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice. 

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2].

Frequently asked questions about losartan

Can I drink alcohol while taking losartan? 
Yes, but alcohol may increase the risk of dizziness or fainting. Drink in moderation[1]. 

Is losartan safe in pregnancy? 
No. Losartan can harm an unborn baby, especially after the first trimester. Speak to your doctor about safer alternatives[1]. 

Can I take losartan long-term? 
Yes. It’s often used for long-term blood pressure or heart condition management. Regular check-ups are important[1]. 

Can I take losartan before surgery? 

Tell your doctor or surgeon if you’re taking losartan, as it can reduce blood pressure when used in combination with general anaesthetics[1]. 

Will losartan affect my contraception? 

It won’t affect your contraception, but it’s not recommended to use the contraceptive patch or combined pill if you have high blood pressure. Speak to your doctor if you’re concerned[1]. 

Can I take losartan with food? 
Yes, it can be taken with or without meals. However, you should avoid salt substitutes such as Lo-Salt that are high in potassium. Avoid drinking grapefruit juice[1]. 

What if I feel dizzy after taking it? 
Sit or lie down until the feeling passes. Avoid driving a car or riding a bike. Let your doctor know if it continues[1]. 

For the official NHS guide for losartan, visit their website.