Losartan (Losartan potassium) – Patient Information (UK)

Losartan is a medicine used to treat certain cardiovascular conditions and to help protect the kidneys in specific patients. It belongs to a group of medicines called angiotensin II receptor blockers (ARBs). Many people take losartan daily as part of long-term care.

This guide explains how losartan works, how it is used, what to expect, and important safety information. If you have any concerns about your own treatment, speak to your doctor or pharmacist.

Quick Facts

• Medicine name: Losartan (losartan potassium)
• Medicine type: Angiotensin II receptor blocker (ARB)
• Main uses (common in the UK): High blood pressure (hypertension), kidney protection in type 2 diabetes with protein in the urine, and certain heart-related indications (as advised by your clinician)
• How it’s taken: Usually once daily, by mouth (tablets)
• Onset: Blood pressure may begin to improve within days; full effect can take several weeks

What Losartan Is

Losartan potassium is the active ingredient in losartan tablets. In the body, losartan blocks the action of angiotensin II, a substance that narrows blood vessels and increases blood pressure.

Losartan is available as tablets in different strengths (the exact options depend on the product you select).

How Losartan Works (Mechanism of Action)

Angiotensin II is part of the body’s renin–angiotensin–aldosterone system (RAAS). It helps regulate blood vessel tone, salt and water balance, and blood pressure.

Losartan blocks angiotensin II at the AT1 receptor. This leads to:

• Widening of blood vessels (reducing vascular resistance)
• Lowering of blood pressure
• Reduced strain on the heart over time
• Kidney protection in suitable patients by reducing the pressures that damage delicate kidney filters

Unlike some other blood pressure medicines, ARBs generally do not cause the dry cough commonly associated with ACE inhibitors.

Pharmacokinetics: How the Body Handles Losartan

“Pharmacokinetics” describes what the body does to the medicine—how it is absorbed, processed, and eliminated.

Absorption

Losartan is absorbed after oral dosing. It is metabolised in the liver to an active metabolite (often referred to as E-3174).

Metabolism

The liver converts losartan to its active metabolite, which contributes to the overall effect. Metabolism involves enzyme pathways in the liver; this is one reason liver function can matter when dosing is considered.

Distribution

Losartan and its metabolites circulate in the bloodstream and bind to proteins to varying degrees.

Elimination

Elimination occurs through the kidneys (urine) and the gut/bile (faeces). The effective duration of action is long enough for many people to take the medicine once daily.

Individual results can vary depending on age, kidney function, liver function, and other medicines taken.

Typical Uses in the UK

Losartan is used for several cardiovascular and kidney-related conditions. Your clinician chooses the indication based on your health history and risk factors.

Common indications include:

• Hypertension (high blood pressure): to lower blood pressure and reduce cardiovascular risk.
• Kidney protection in type 2 diabetes: in people who have protein in the urine (proteinuria), helping slow progression of kidney disease.
• Certain heart failure or heart-related indications: depending on clinical assessment and suitability, including when specific options are not appropriate.

Treatment plans in the UK are typically aligned with national clinical guidance and local formularies.

How to Take Losartan: Timing and Practical Advice

Many people take losartan once daily. Consistency is important—try to take it at the same time each day.

When to take it

• Any time of day can work, but pick a time that suits your routine.
• If it makes you feel a little light-headed, some people prefer taking it in the evening—however, discuss this with your pharmacist if symptoms occur.
• If you forget a dose, take it when you remember unless it is close to the time for your next dose (in which case skip the missed dose).

How to take it

• Swallow the tablet with water.
• You can usually take losartan with or without food.
• Keep taking it regularly even if you feel well—blood pressure often has no symptoms.

How long until it works?

Blood pressure may start to improve within a few days. The full effect can take several weeks. Kidney benefits and longer-term cardiovascular protection occur over months to years.

Dosing: What Is Typical?

The exact dose depends on the condition being treated, your age, blood pressure response, and kidney/liver function. Dosing decisions should be made with your clinician.

Common dosing approaches (general guidance):

• Hypertension: often started at a standard daily dose and then adjusted based on blood pressure measurements.
• Kidney protection in type 2 diabetes (proteinuria): dose selection is individualised; your doctor may start at a particular strength and adjust if needed.
• Older adults: dose may be adjusted based on overall health and kidney function.

If you are uncertain about your personal dose, check the label on your medicine pack or speak to your pharmacist.

Food Interactions

Food generally does not have a major interaction with losartan. This means you can usually take it with or without meals.

The most important factors are usually kidney and liver function and interactions with other medicines (see below).

Alcohol and Medicine Interactions

Alcohol

Alcohol can lower blood pressure and may increase the chance of dizziness or light-headedness, especially when you first start treatment or if your dose is increased. For many people, moderate alcohol is compatible, but it’s wise to be cautious.

• Avoid heavy drinking, particularly early in treatment.
• If you feel faint or dizzy, reduce alcohol and speak to your pharmacist or clinician.

Medicine interactions

Losartan can interact with other medicines that affect blood pressure, potassium levels, kidney function, or fluid balance. Tell your pharmacist about all medicines you take, including over-the-counter products and herbal supplements.

Important interaction groups include:

• Potassium-raising medicines: e.g., potassium supplements, potassium-sparing diuretics (such as spironolactone or amiloride), and some salt substitutes that contain potassium. This can increase the risk of high potassium (hyperkalaemia).
• NSAIDs (painkillers such as ibuprofen or naproxen): regular or high-dose NSAID use can affect kidney function and may reduce blood pressure-lowering effect. Caution is especially important if you are dehydrated or have existing kidney issues.
• Diuretics: “water tablets” can contribute to dehydration or lower blood pressure. Your clinician may need to adjust doses or monitor you more closely at start.
• Other blood pressure medicines: combined therapy may increase the chance of dizziness or low blood pressure but may be appropriate depending on your condition.
• Lithium: lithium levels can become elevated when combined with some RAAS medicines. Close monitoring is needed if the combination is used.
• Aliskiren: combination with certain RAAS medicines may not be suitable, depending on circumstances. Your clinician will advise if relevant.

If you’re unsure whether a particular medicine is an NSAID or contains potassium, ask your pharmacist.

Safety Profile: Side Effects and When to Get Help

Like all medicines, losartan can cause side effects. Many are mild and improve as your body adjusts. Some side effects require prompt medical attention.

Common or mild side effects

• Dizziness, especially when standing up quickly
• Low blood pressure symptoms such as light-headedness
• Tiredness
• Headache
• Changes in blood test results (such as potassium or kidney function markers)

Less common but important risks

• High potassium (hyperkalaemia): may show up in blood tests. Symptoms can include muscle weakness or unusual heart rhythm.
• Kidney function changes: particularly in people with existing kidney disease, dehydration, or when combined with certain medicines (e.g., NSAIDs or diuretics).
• Allergic-type reactions (rare): swelling of face/lips, difficulty breathing, or severe rash needs urgent assessment.
• Angioedema (rare): swelling under the skin, often around eyes and lips, or swelling affecting breathing. Seek urgent help if this occurs.

Seek urgent medical help if you have:

• Signs of severe allergic reaction (e.g., swelling of face/lips, trouble breathing)
• Severe dizziness/fainting
• Chest pain, severe shortness of breath, or symptoms suggesting a serious heart rhythm problem
• Severe symptoms of very high potassium, such as profound weakness or palpitations (if advised by a clinician)

Monitoring (blood tests)

Your clinician may check kidney function (creatinine/eGFR) and potassium levels, particularly after starting treatment or changing dose. This is a normal safety measure.

Practical Tips for Safe, Effective Use

• Check your blood pressure regularly if advised. Home monitoring helps your doctor adjust treatment.
• Stand up slowly if you feel dizzy, especially in the first days of treatment.
• Stay hydrated unless your clinician has restricted fluids. Dehydration can increase the risk of kidney issues.
• Keep track of medicines you use for pain. If you frequently take ibuprofen/naproxen, ask whether an alternative is safer for you.
• Avoid potassium salt substitutes unless your doctor has said they’re safe.
• Don’t stop suddenly without advice—blood pressure may rise again.
• Attend blood test appointments if scheduled.

Special Considerations

Pregnancy and breastfeeding

RAAS medicines can be harmful to an unborn baby. If you are planning a pregnancy or could become pregnant, speak to your clinician as early as possible for safer alternatives.

If you are breastfeeding, discuss with your clinician; suitability depends on your health profile and the specific medicine used.

Kidney disease

Losartan may be used in kidney-related conditions, but kidney function and potassium levels must be monitored. Your dose may be adjusted based on test results.

Liver impairment

Since losartan is processed by the liver, liver impairment may affect dosing decisions. Your clinician will advise the safest approach.

Dehydration, vomiting, or diarrhoea

If you become significantly dehydrated (for example, due to illness with vomiting or diarrhoea), you may need extra monitoring. If you feel unwell and are at risk of dehydration, contact your healthcare team for guidance.

Alternative Options (If Losartan Is Not Suitable)

Treatment choices depend on your condition, side-effect history, and what other medicines are appropriate for you. If losartan is not suitable, clinicians may consider other options such as:

• Other ARBs: e.g., candesartan, valsartan, telmisartan, depending on availability and suitability.
• ACE inhibitors: e.g., lisinopril/enalapril (may cause cough in some people).
• Calcium channel blockers: e.g., amlodipine for blood pressure control.
• Thiazide-like diuretics: e.g., indapamide or chlortalidone in selected patients.
• Other heart failure treatments: depending on the exact diagnosis and guidelines (may include beta-blockers and others).

Do not switch medicines on your own. Your pharmacist or doctor can help ensure the transition is safe.

UK Market and Legal Context (Overview)

Losartan is a widely used medicine in the UK for cardiovascular and kidney-related indications. In the UK, medicines are regulated and dispensed according to the Medicines and Healthcare products Regulatory Agency (MHRA) requirements and guidance.

Availability may vary between brands and strengths. Pharmacy supply is typically subject to pharmacy procedures and clinical suitability checks.

The UK also follows evidence-based clinical pathways and prescribing frameworks that may influence first-line and combination choices.

Recent Guidance and Clinical Updates (General Themes)

Over time, UK clinical practice continues to emphasise:

• Using RAAS medicines appropriately for suitable patients (e.g., kidney protection in appropriate diabetes cases).
• Monitoring kidney function and potassium after initiation and dose changes.
• Avoiding inappropriate combinations that increase risk (for example, unnecessary dual RAAS blockade).
• Considering safer alternatives in pregnancy and during breastfeeding.

Your healthcare team will base decisions on current evidence and local guidance.

Delivery, Availability, and Product Condition (Online Pharmacy)

Losartan tablets are typically available in the UK through authorised supply routes. On an online pharmacy, availability depends on stock levels and the specific strength/brand you select.

• Delivery: Delivery options and timescales vary by provider, location, and courier service.
• Packaging: Medicines are usually supplied in original packaging with clear labelling, patient information, and batch details where relevant.
• Storage: Follow storage instructions on the pack (commonly keep below a specified temperature, protect from moisture, and keep out of reach of children).

If you have urgent need of your medicine, contact the pharmacy support team before ordering so you can confirm delivery options.

FAQ – Frequently Asked Questions

1) Is losartan the same as losartan potassium?

Yes. Losartan potassium is the chemical form used in tablets. It’s commonly referred to simply as losartan.

2) How quickly will my blood pressure improve?

Some improvement can begin within days, but the full effect may take up to several weeks. Keep taking it regularly and monitor as advised.

3) Can I take losartan with food?

Yes. You can generally take losartan with or without food.

4) What should I do if I miss a dose?

Take it when you remember unless it is nearly time for your next dose. If it’s close to the next dose, skip the missed one. Do not take a double dose.

5) Will losartan make me dizzy?

Dizziness can happen, especially when starting or increasing the dose. Stand up slowly. If dizziness is frequent, severe, or affects your daily activities, speak to a healthcare professional.

6) Do I need blood tests?

Blood tests may be recommended to check kidney function and potassium, particularly after starting or adjusting treatment.

7) Can I drink alcohol while taking losartan?

Moderate alcohol may be compatible for many people, but alcohol can worsen light-headedness. Avoid heavy drinking and seek advice if you notice symptoms.

8) Are NSAIDs like ibuprofen safe with losartan?

Occasional use may be acceptable for some people, but regular or high-dose NSAID use can increase risk to kidney function and may affect blood pressure control. Ask your pharmacist for advice tailored to you.

9) What if I’m on a potassium supplement?

Combining losartan with potassium supplements can raise potassium levels. Do not change or stop supplements without medical advice—your clinician may monitor potassium or adjust your regimen.

10) Can I take losartan if I have kidney disease?

Losartan may be used in kidney conditions, but dosing and monitoring are important. Your blood tests and eGFR help guide safe use.

11) Is losartan suitable during pregnancy?

RAAS medicines are generally not recommended during pregnancy. If pregnancy is possible, discuss options promptly with your clinician.

12) What are common alternatives if losartan doesn’t suit me?

Alternatives may include other ARBs, ACE inhibitors, calcium channel blockers, or diuretics—depending on your condition and risk profile.

Summary

Losartan (losartan potassium) is an ARB commonly used in the UK for high blood pressure and for kidney/cardiovascular protection in selected patients. It works by blocking angiotensin II at the AT1 receptor, helping relax blood vessels and reduce strain on the heart and kidneys.

For safe and effective use, take it consistently, be mindful of interactions (especially medicines that affect potassium or kidney function), and attend any recommended blood test monitoring. If you experience significant dizziness, swelling, or other concerning symptoms, seek medical advice promptly.