Losartan Tablets

Treating high blood pressure consistently over time helps to protect the heart, blood vessels, and kidneys from serious damage. Losartan tablets are a prescription-only angiotensin receptor blocker (ARB) used in adults for several cardiovascular indications including hypertension, cardiovascular risk reduction in patients with left ventricular hypertrophy, and kidney protection in adults with type 2 diabetes and established kidney disease. Losartan is one of the most widely prescribed ARBs in the UK and features prominently in antihypertensive medication guidelines. A prescription can only be issued following a clinical consultation.

Losartan tablets are an oral prescription medicine containing losartan potassium as the active ingredient. Losartan was the first ARB to be developed and approved for clinical use and belongs to the angiotensin receptor blocker class of medicines, also known as angiotensin II receptor antagonists. The ARB class is widely used in cardiovascular therapy.

Losartan is licensed in the UK for three distinct indications. First, it is used for the treatment of hypertension (high blood pressure). Second, it is used for the reduction of cardiovascular morbidity and mortality in hypertensive patients with left ventricular hypertrophy (thickening of the heart's main pumping chamber), as evidenced by clinical outcomes data including the LIFE study. Third, it is used for the treatment of kidney disease in adults with type 2 diabetes who have high blood pressure and nephropathy.

Losartan is available as a generic medicine from multiple manufacturers. Four strengths are available through this service: 12.5 mg, 25 mg, 50 mg, and 100 mg. The wide range of strengths allows careful dose titration across all three licensed indications.

Losartan works by blocking the angiotensin II receptor, a key target in the renin angiotensin system. This hormonal pathway plays a central role in regulating blood pressure and protecting end organs such as the heart and kidneys.

Angiotensin II and Blood Pressure

Angiotensin II is a hormone that causes blood vessels to narrow and the body to retain sodium and water. It does this primarily by binding to the AT1 receptor found in blood vessel walls, the heart, and the kidneys. The result is raised blood pressure and, over time, harmful structural changes to the heart and kidneys.

Losartan and AT1 Receptor Blockade

Losartan selectively blocks the AT1 receptor without activating it. By occupying this receptor, losartan prevents angiotensin II from binding and exerting its effects. Blood vessels relax and widen, sodium and water retention decreases, and blood pressure falls. In the left ventricle, reduced angiotensin II activity over time can help to reduce the pathological thickening of the heart muscle associated with left ventricular hypertrophy.

Unlike ACE inhibitors, losartan does not inhibit the breakdown of bradykinin. This is why losartan does not typically cause the dry persistent cough associated with ACE inhibitors such as lisinopril or ramipril. Losartan is therefore a suitable alternative for patients who cannot tolerate an ACE inhibitor due to cough. Losartan is also converted in the body to an active metabolite called E-3174, which contributes significantly to its blood pressure lowering effect and has a longer duration of action than losartan itself.

Always take losartan exactly as your prescriber instructs. The information below summarises key points from the current UK SmPC. Read the Patient Information Leaflet supplied with your medicine before starting treatment.

• Take losartan once daily, at approximately the same time each day.
• Losartan can be taken with or without food.
• Swallow the tablet whole with a glass of water.
• If you miss a dose, take it as soon as you remember on the same day. If you only remember the following day, skip the missed dose and continue with your normal schedule. Do not take two doses on the same day.
• Do not stop taking losartan without speaking to your prescriber first. Blood pressure and the conditions losartan is used to treat require ongoing management.
• Depending on the indication and your individual circumstances, your prescriber may start you at a lower dose and increase it gradually. Blood pressure should be reviewed regularly, and kidney function and potassium levels may be checked periodically. Attend all follow up appointments so that your response to treatment can be monitored safely.

Losartan is available in four strengths, reflecting the wide range of doses used across its licensed indications. All dose decisions are made by your prescriber.

Losartan 12.5 mg Tablets

The 12.5 mg tablet is the lowest available strength. It is typically used as a starting dose in patients who may be at increased risk of a significant blood pressure drop with their first dose, particularly patients with heart failure, volume depletion, or significant kidney impairment. Starting at 12.5 mg allows very careful dose titration. This strength is also used when a small incremental dose increase from 25 mg is needed.

Losartan 25 mg Tablets

The 25 mg tablet is a common starting dose for many patients. In patients with heart failure or those with significant volume depletion, starting at 25 mg allows assessment of tolerability before any increase. Some patients who are more sensitive to blood pressure lowering medicines may be maintained at 25 mg.

Losartan 50 mg Tablets

The 50 mg tablet is the standard starting and maintenance dose for most adults with hypertension. For hypertension, the usual dose is 50 mg once daily. If blood pressure is not adequately controlled after several weeks, the dose may be increased to 100 mg. For diabetic nephropathy, the SmPC recommends starting at 50 mg once daily.

Losartan 100 mg Tablets

The 100 mg tablet is the maximum recommended daily dose for both hypertension and diabetic nephropathy. For the left ventricular hypertrophy cardiovascular risk reduction indication, the SmPC target dose is 50 mg once daily, with the option to add a low dose diuretic if further blood pressure reduction is needed. Do not take more than 100 mg per day without specific medical instruction. All dose adjustments are made by your prescriber.

Like all medicines, losartan can cause side effects, although not everyone experiences them. The information below is based on the current UK SmPC. Refer to the Patient Information Leaflet for the full list of side effects.

Common Side Effects (may affect up to 1 in 10 people)

• Dizziness, particularly on standing up quickly
• Raised blood potassium (hyperkalaemia), which may cause muscle weakness or palpitations. This is more likely in patients with kidney disease, diabetes, or those taking potassium supplements or potassium-sparing diuretics.
• Changes in kidney function, particularly at the start of treatment in patients with pre existing kidney impairment
• Hypoglycaemia (low blood sugar) in patients with type 2 diabetes and nephropathy who are taking losartan

Uncommon Side Effects (may affect up to 1 in 100 people)

• Low blood pressure (hypotension), particularly in patients who are dehydrated or on diuretics
• Headache
• Fatigue
• Nausea or abdominal pain
• Skin rash

Rare and Serious Side Effects

Unlike ACE inhibitors, losartan does not commonly cause a dry cough. However, a small number of patients may develop a cough. Angioedema (swelling of the face, lips, tongue, or throat) has been reported rarely with ARBs, including losartan.

Go to your nearest accident and emergency department or call 999 immediately if you experience:

• Sudden swelling of the face, lips, tongue, or throat. This is angioedema and requires immediate emergency medical attention.
• Signs of severely raised potassium such as muscle weakness, irregular heartbeat, or confusion
• A significant reduction in urine output, which may indicate worsening kidney function

Report any suspected side effect to your prescriber, pharmacist, or via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk.

Losartan Tablets May Be Suitable If You:

• Are an adult with a confirmed diagnosis of hypertension
• Have hypertension with left ventricular hypertrophy and your prescriber has determined cardiovascular risk reduction treatment is appropriate
• Have type 2 diabetes with high blood pressure and established kidney disease
• Cannot tolerate ACE inhibitors due to a persistent dry cough and require an antihypertensive medication in the ARB class
• Are already prescribed losartan and require a repeat prescription through an online prescribing service

Losartan Tablets Are Not Suitable If You:

• Are pregnant or planning to become pregnant. Losartan is contraindicated in pregnancy. ARBs cause serious harm to the developing baby, particularly in the second and third trimesters, including kidney damage, skull abnormalities, and foetal death. Contact your prescriber immediately if you become pregnant while taking losartan.
• Are breastfeeding
• Have severe liver impairment
• Have diabetes or moderate to severe kidney impairment and are also taking aliskiren. This combination is contraindicated.
• Have a known allergy or hypersensitivity to losartan or any excipient listed in the SmPC
• Are under 18 years of age (this service is for adults only)

Tell your prescriberabout all medicines you take, including over the counter products and herbal supplements. The following interactions are of particular clinical importance:

• Potassium supplements, potassium-sparing diuretics (such as spironolactone or amiloride), and potassium-containing salt substitutes: these can raise blood potassium to dangerous levels when combined with losartan.
• NSAIDs such as ibuprofen: regular use may reduce the blood pressure lowering effect of losartan and increase the risk of kidney problems, particularly in older patients or those with reduced kidney function.
• Lithium: ARBs can increase lithium blood levels, raising the risk of lithium toxicity. Close monitoring is required if this combination is used.
• Aliskiren: contraindicated in combination with losartan in patients with diabetes or significant kidney impairment.
• Other antihypertensive medicines and diuretics: additive blood pressure lowering effects should be considered, particularly at the start of treatment.
• Fluconazole and rifampicin: these medicines can affect the metabolism of losartan and its active metabolite. Your prescriber will be aware of relevant interactions and will factor them into their clinical assessment.

Your prescriber will review all current medicines during the clinical assessment before any prescription is considered.

Losartan is a Prescription Only Medicine. The clinical consultation is the essential first step. A prescription will only be issued if a registered prescriber concludes, based on their individual assessment of your circumstances, that losartan is clinically appropriate for you.

During your online consultation with Pharmacy Planet, a registered prescriber will review the information you provide. This includes your blood pressure history, any relevant cardiac or renal diagnoses, whether you have type 2 diabetes with kidney disease, your current medicines, kidney function and potassium results where available, and other relevant medical history. Based on this, the prescriber will decide whether losartan is appropriate, which strength is suitable, and whether the online service is appropriate for your situation.

If you are under the care of your GP, a cardiologist, or a nephrologist for any of the conditions losartan is used to treat, please keep them informed of all medicines prescribed through online services. Coordinated care supports the safest approach to BP regulation and cardiovascular therapy.

• Store below 30°C.
• Store in the original packaging to protect from moisture and light.
• Keep out of the sight and reach of children.
• Do not use after the expiry date printed on the packaging.
• Do not dispose of medicines via household waste or wastewater. Return unused or out of date tablets to your pharmacist for safe disposal.
• Full storage instructions are provided in the Patient Information Leaflet supplied with your medicine.

The table below compares ARB tablets and Rasilez (aliskiren), the only direct renin inhibitor licensed for hypertension in the UK. All act on the renin-angiotensin-aldosterone system (RAAS) and are taken once daily as tablets.

Important: This comparison is for general information only and does not replace medical advice. A prescriber will decide which treatment is suitable for you following an online consultation.

Pharmacy Planet is a GPhC-registered online pharmacy providing access to prescription medicines through a clinically led consultation process. Our registered prescribers and pharmacists are committed to patient safety, clinical accuracy, and responsible prescribing.

We follow GPhC standards, MHRA guidance, and ASA advertising regulations in all aspects of our service. Every prescription is reviewed and dispensed by qualified healthcare professionals. We provide clear, factual information to help patients understand their antihypertensive medication and make informed decisions about their cardiovascular therapy and heart health.

If you have questions about losartan or any other medicine, our pharmacy team is available to help. We are committed to transparent, patient centred care.

References

1. Electronic Medicines Compendium (eMC). Losartan 12.5 mg, 25 mg, 50 mg and 100 mg tablets — Summary of Product Characteristics. https://www.medicines.org.uk/emc. Accessed May 2026.
2. National Institute for Health and Care Excellence (NICE). Hypertension in adults: diagnosis and management. NICE guideline NG136. https://www.nice.org.uk/guidance/ng136. Accessed May 2026.
3. NHS. High blood pressure (hypertension). https://www.nhs.uk/conditions/high-blood-pressure-hypertension. Accessed May 2026.
4. Joint Formulary Committee. British National Formulary (BNF). Losartan potassium. BMJ Group and Pharmaceutical Press. https://bnf.nice.org.uk. Accessed May 2026.
5. Medicines and Healthcare products Regulatory Agency (MHRA). Yellow Card — report a side effect. https://yellowcard.mhra.gov.uk. Accessed May 2026.