Losartan (Losartan Potassium) – Patient Information

Losartan potassium is a prescription medicine used to treat conditions affecting the heart, blood vessels and kidneys. This page explains how it works, how it’s typically taken, and what to consider for safe use in the United Kingdom.

If you are unsure about your dose or how to take your medicine, check the information provided with your product or speak to a pharmacist.

1) Basic product information

*Strengths differ between products. Use the strength you have been given and follow your dosing instructions.

2) How losartan works (mechanism of action)

Losartan belongs to a group of medicines called angiotensin II receptor blockers (ARBs). In the body, the hormone angiotensin II helps tighten blood vessels and increases salt and water retention. This raises blood pressure and can strain the heart and kidneys.

Losartan blocks the action of angiotensin II at its main receptor (AT1 receptor). This helps:

• Lower blood pressure by relaxing blood vessels
• Reduce strain on the heart and improve symptoms in some people with heart failure
• Protect the kidneys in certain high-risk patients (especially where diabetes and protein in the urine are present)

3) Pharmacokinetics – what the body does to losartan

“Pharmacokinetics” describes how the medicine is absorbed, processed and removed from the body.

• Absorption: After taking a tablet, losartan is absorbed from the digestive tract. Taking with food does not usually prevent absorption, although timing can affect how quickly levels rise for some people.
• Metabolism: Losartan is metabolised in the liver to form an active metabolite (often called EXP-3174), which also contributes to blood-pressure effects.
• Distribution: The medicine circulates in the bloodstream and reaches tissues involved in cardiovascular and kidney function.
• Elimination: Losartan and its metabolites are removed mainly via the bile and faeces (with some excretion through the kidneys). Clearance can be affected by liver function.
• Half-life (duration of action): Losartan’s effects last long enough that many people take it once daily, though individual response varies.

Your doctor may adjust the dose if you have liver problems or other relevant conditions.

4) Typical uses and who it may be for

Losartan is used for several cardiovascular and kidney-related conditions. The exact choice of medicine and dose depends on your health history and test results.

4.1 High blood pressure (hypertension)

Losartan helps reduce elevated blood pressure, lowering the risk of complications such as stroke, heart disease and kidney problems.

4.2 Heart failure

In some patients with heart failure, losartan can help improve symptoms and reduce risk of hospitalisation, particularly if other medicines are not suitable.

4.3 Kidney protection in certain people with diabetes

Losartan may be used to help protect kidney function in people with type 2 diabetes and signs of kidney stress (for example, protein in the urine), depending on overall treatment plan.

5) Indications (when losartan is prescribed)

In the UK, losartan is indicated for:

• Treatment of hypertension in adults and in some situations for children and adolescents, where appropriate.
• Heart failure in adults when an ARB is considered suitable.
• Renal protection in certain adult patients with diabetes and evidence of kidney disease (as defined in the product licence/clinical guidance).

Your clinician will tailor the approach based on guideline recommendations and your individual risk factors.

6) Dosing: typical starting doses and how to take it

Always follow the dose on your label or the instructions you were given. The information below describes common patterns.

6.1 Typical adult dosing for hypertension

• Common starting dose: once daily.
• Possible adjustment: the dose may be increased gradually depending on your blood pressure and tolerance.

6.2 Heart failure

• Often started low to reduce the chance of dizziness or low blood pressure.
• Up-titration may follow based on symptoms, blood pressure and blood tests.

6.3 Diabetes with kidney protection

• Dose is chosen to achieve kidney protection targets while monitoring potassium and kidney function.

6.4 Children and adolescents

Losartan may be used in paediatric patients for hypertension in certain circumstances. Dosing is weight-based and requires careful monitoring.

6.5 Timing and missed doses

Timing: Losartan is usually taken once daily, at about the same time each day. You can take it morning or evening—choose what best suits you and your routine.

If you miss a dose:

• If you remember on the same day, take it when you remember.
• If it is almost time for the next dose, skip the missed dose and take the next one at the usual time.
• Do not take a double dose to make up for the missed tablet.

If you frequently miss doses, speak to a pharmacist about reminders or blister packing options.

7) Food interactions and what to expect

Losartan can be taken with or without food. Food does not usually significantly change how the medicine works.

That said, some people notice they feel slightly more dizzy when starting treatment, especially if they also have dehydration or are already taking other blood-pressure-lowering medicines. If dizziness occurs, taking your dose at a time when you’re more likely to be resting can help you manage it while your body adjusts.

8) Alcohol and medicine interactions

8.1 Alcohol

Alcohol may lower blood pressure further and can increase the risk of dizziness or light-headedness, particularly when you first start losartan or when your dose is increased.

To reduce the chance of side effects:

• Consider limiting alcohol, especially during the first few weeks of therapy.
• Stand up slowly if you feel light-headed.
• Avoid binge drinking.

8.2 Common medicine interactions

Losartan can interact with other medicines, particularly those affecting kidney function and potassium levels, or those that also lower blood pressure.

Tell your pharmacist or prescriber if you take:

• Potassium supplements or salt substitutes containing potassium
• Other medicines that increase potassium (some diuretics, certain heart medicines)
• Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or diclofenac (regular/high-dose use may affect kidney function and reduce antihypertensive effects)
• Other blood pressure medicines (may increase the chance of low blood pressure)
• Diuretics (“water tablets”), especially when starting therapy (may contribute to low blood pressure)
• Lithium (requires close monitoring)
• Medicines affecting the liver (since losartan is metabolised in the liver)
• Other RAAS medicines (rarely, combining can increase risk of kidney problems and high potassium)

This is not a complete list. Always check interactions for any new medicine, including over-the-counter products and herbal remedies.

9) Safety profile: important cautions and side effects

Like all medicines, losartan can cause side effects. Many people tolerate it well, but it’s important to know what to watch for.

9.1 Common side effects

• Dizziness or light-headedness (especially at the start or after dose increases)
• Low blood pressure symptoms (feeling faint)
• Fatigue
• Headache

9.2 Less common but important effects

• Increased potassium in the blood (hyperkalaemia), which may be detected by blood tests
• Changes in kidney function (also monitored via blood tests)
• Gastrointestinal symptoms such as nausea or stomach upset (varies by person)

9.3 Seek urgent medical advice if

• Signs of allergy such as swelling of the face/lips, rash, or breathing difficulties
• Severe dizziness, fainting, or chest pain
• Marked weakness or abnormal heartbeats (possible potassium imbalance)
• Very little urine or sudden worsening of kidney-related symptoms

9.4 Pregnancy and breastfeeding

Losartan is not recommended in pregnancy due to risks to the developing baby. If you are planning pregnancy, already pregnant, or could become pregnant, discuss this promptly with a clinician.

Breastfeeding guidance depends on the specific medicine and your situation—speak with a pharmacist or prescriber for personalised advice.

9.5 Kidney and liver conditions

• If you have kidney artery narrowing or significant kidney impairment, you may need extra monitoring.
• If you have liver impairment, your clinician may choose a lower starting dose and monitor more closely.

10) Practical use tips for getting the best results

• Measure your blood pressure if you’ve been advised to. Keep a note of readings to help your clinician adjust treatment.
• Don’t stop suddenly without advice—blood pressure may rise again.
• Attend blood tests (kidney function and potassium). These are especially important when starting, after dose changes, or if you become unwell.
• Stay hydrated during hot weather or illness unless your doctor has restricted fluids.
• Be careful with dehydration (e.g., vomiting/diarrhoea). Dehydration can increase the risk of kidney-related side effects.
• Use the same routine daily to avoid missed doses.

11) When to be extra careful (illness, vomiting/diarrhoea, surgery)

If you develop a serious illness (for example, persistent vomiting or diarrhoea), your blood pressure and kidney function can change quickly. In these situations, some people need temporary review of medicines that affect the kidney and blood pressure.

Speak to a clinician promptly if you become very unwell, especially if you:

• cannot keep fluids down
• have reduced urine output
• feel faint when standing
• experience severe weakness or palpitations

12) Alternative options to consider

Depending on your condition and medical history, a prescriber may consider other blood-pressure or heart/kidney-protecting medicines. Options may include:

• ACE inhibitors (another class that targets the renin–angiotensin system)
• Other ARBs (similar mechanism, different active ingredient)
• Calcium channel blockers
• Thiazide-type diuretics
• Beta blockers (particularly in certain heart conditions)

Your clinician will select the option that best fits your goals and tolerability, including blood test results and other medicines you take.

13) United Kingdom: market and legal context

In the UK, medicines containing losartan are regulated and supplied according to national medicines legislation and professional standards. Information on licensed indications, dosing and warnings is provided in the product’s Summary of Product Characteristics (SmPC) and patient-facing materials.

Clinical recommendations for treating hypertension, heart failure and diabetic kidney disease are supported by UK and international guidance, and may be updated as new evidence emerges.

14) Recent guidance and ongoing monitoring

Treatment pathways for blood pressure and cardiovascular risk typically emphasise:

• Individualised targets based on age, comorbidities and overall cardiovascular risk
• Regular review after starting or changing doses
• Monitoring kidney function and potassium when using RAAS-influencing medicines (including ARBs)
• Medication safety during acute illness (e.g., dehydration) and when combining with interacting medicines

Your healthcare team may also review your overall regimen (e.g., diet, salt intake, lifestyle measures, and other cardiovascular medicines).

15) Delivery and availability in the UK

Losartan products may be available from pharmacies and online pharmacy services. Availability can vary by brand and tablet strength.

• Delivery: delivery times depend on supplier and your location across the UK.
• Packaging: medicines are usually dispatched in protective packaging to keep them secure during transit.
• Stock levels: if a specific strength or brand is temporarily unavailable, you may be offered an alternative that contains the same active ingredient (subject to availability and the rules applicable to your supply).

When ordering online, ensure you select the correct strength, quantity and form matching your prescribed regimen.

16) FAQ – Frequently asked questions

How quickly does losartan start working?

Many people begin to notice blood pressure changes within the first days to weeks. Full benefit can take longer. If you’re monitoring at home, your readings may gradually improve over time.

Should I take losartan every day?

Yes. Losartan is usually taken daily to keep blood pressure and cardiovascular risk under control. Missing doses can reduce effectiveness.

Can I take losartan with food?

Yes. Losartan can be taken with or without food.

What should I do if I feel dizzy?

Sit or lie down until the dizziness passes. If dizziness is frequent, severe, or you feel faint, contact a healthcare professional. Dizziness is more likely at the start of treatment or after dose increases.

Will I need blood tests?

Often, yes. Blood tests help check kidney function and potassium levels, particularly after starting losartan or changing the dose, or if you become unwell.

Can I take ibuprofen or other painkillers?

Some NSAIDs (like ibuprofen) may affect kidney function and interact with blood-pressure medicines in certain circumstances, especially with regular/high-dose use. If you need pain relief, ask a pharmacist what is safest for you.

Is there a “best time” of day to take losartan?

Many people take it once daily at a consistent time. Choose a time that helps you remember it. If dizziness occurs, your pharmacist may suggest taking it at a time that best suits your routine (for example, when you’re less likely to be standing for long periods).

Can I drink alcohol while taking losartan?

Moderate alcohol may be possible for some people, but alcohol can increase the chance of dizziness and low blood pressure. If you experience light-headedness, reduce alcohol and speak to a pharmacist or clinician.

What happens if I stop taking losartan?

Stopping can cause your blood pressure to rise again and may reduce protective benefits for the heart and kidneys. Do not stop without medical advice.

Who should not take losartan?

Losartan may not be suitable for everyone. It may be unsuitable if you have had an allergic reaction to an ARB, certain pregnancy situations, or specific kidney/liver conditions without close supervision. Your clinician will consider your medical history and blood test results.

Are there alternatives if losartan doesn’t suit me?

Yes. Alternatives may include different ARBs, ACE inhibitors, calcium channel blockers, or other medicines depending on why you’re taking losartan and how you respond.

17) Summary

Losartan (losartan potassium) is an ARB medicine widely used in the UK to treat high blood pressure, support some cases of heart failure, and help protect kidney function in selected patients—particularly where diabetes and protein in the urine are present.

• Take it once daily, usually at the same time each day.
• Food does not usually matter; you can take it with or without meals.
• Be mindful of alcohol and medicines that can affect kidneys or potassium.
• Blood tests may be needed to ensure safe kidney and potassium levels.

If you have questions about your specific product, dose, or side effects, a pharmacist can help.