Losartan: Uses, Side Effects & Safety

What it is and what it's used for

Losartan belongs to the angiotensin receptor blocker (ARB) group of blood-pressure medicines and was the first medicine of its kind. Its main use is treating high blood pressure. It is also prescribed to slow kidney damage in people with type 2 diabetes and high blood pressure, and to lower the risk of stroke in people with hypertension and thickening of the heart's main pumping chamber.

Losartan is a prescription-only medicine in India, usually taken once daily for the long term. Because high blood pressure usually has no symptoms, treatment is about preventing future harm — stroke, heart attack, heart failure, and kidney damage — rather than relieving anything you feel today.

How it works (simple language)

A hormone called angiotensin II narrows blood vessels and raises blood pressure. Losartan blocks the receptors this hormone acts on, so blood vessels stay relaxed and open, and blood pressure falls. By easing the pressure on artery and kidney walls, it also helps protect the kidneys and the heart over time.

Dosage forms available in India (general info only)

In India, losartan is commonly available as 25 mg, 50 mg and 100 mg tablets. You may know it by brand names such as Losar or Covance — brands vary by region and manufacturer, and the medicine inside is the same losartan. It is taken once a day, with or without food.

Never decide the dose yourself from this article. Always follow your doctor's prescription or the directions on the pack, and check with your pharmacist if you are unsure — especially for children, where the dose depends on the child's weight and age.

Side effects

Common: Dizziness or light-headedness (especially when standing up quickly), a stuffy nose or sinus-type symptoms, back pain, leg or muscle cramps, and tiredness are the most commonly reported side effects.

Serious — seek medical care: Swelling of the face, lips, tongue, or throat, or difficulty breathing, can signal a rare allergic reaction (angioedema) — seek emergency care immediately. Passing very little urine, swelling of the legs or feet, muscle weakness, or an irregular heartbeat can indicate kidney problems or dangerously high potassium — contact your doctor promptly.

Precautions and warnings

• Never use in pregnancy. Losartan can cause serious harm or death to an unborn baby, especially in the second and third trimesters. Women who could become pregnant should use effective contraception and tell their doctor immediately if pregnancy occurs.
• Watch your potassium. Losartan can raise blood potassium. Avoid potassium supplements and potassium-based salt substitutes unless your doctor specifically approves them.
• Kidney and liver disease: Tell your doctor if you have kidney problems, liver problems, or narrowing of the kidney arteries — monitoring or a different medicine may be needed.
• Dehydration risk. Vomiting, diarrhoea, or very low fluid intake while on losartan can lower blood pressure too much and strain the kidneys. Contact your doctor if you become dehydrated.
• Stand up slowly. Rise slowly from sitting or lying down to avoid dizziness or fainting, especially when starting treatment or after a dose change.
• Keep taking it daily. Losartan protects you only while you take it. Do not stop without your doctor's advice — blood pressure can rebound.
• Surgery and procedures: Tell your doctor or anaesthetist that you take losartan before any surgery.

Interactions (general)

Losartan can interact with several medicines. NSAID painkillers (such as ibuprofen and diclofenac) can blunt its blood-pressure effect and harm the kidneys when combined. Potassium-sparing diuretics, potassium supplements, and trimethoprim-containing medicines can push potassium dangerously high. It can also raise lithium levels. Always tell your doctor or pharmacist about *all* medicines you take — including ayurvedic, herbal, and over-the-counter products — so they can check for interactions.

Pregnancy and breastfeeding (general guidance)

Losartan must not be used during pregnancy — it can seriously harm or kill the developing baby. It is also not recommended while breastfeeding, as safer alternatives are available. If you are pregnant, planning pregnancy, or breastfeeding, consult your doctor first; do not stop a blood-pressure medicine on your own without guidance on a replacement.

Storage

Store tablets at room temperature, away from moisture and direct sunlight, in their original pack. Keep all medicines out of the reach and sight of children. Check the expiry date and do not use expired medicine.

When to see a doctor

See a doctor if: you feel faint or very dizzy; you notice swelling of the face, lips, or tongue; you pass very little urine; your legs or feet swell; you have persistent vomiting or diarrhoea; or you experience muscle weakness or an irregular heartbeat. Seek emergency care immediately for swelling of the face, lips, tongue, or throat, or difficulty breathing.

FAQs

1. What is the difference between losartan and telmisartan?

Both are ARBs that lower blood pressure by blocking angiotensin II. They differ in how long they act and in approved uses — for example, telmisartan is also used for stroke-risk reduction in certain high-risk patients. Your doctor chooses based on your condition, other medicines, and response.

2. What should I do if I miss a dose?

Take it when you remember, unless it is nearly time for your next dose — then skip the missed one and continue normally. Never take two doses together.

3. Can I take losartan with painkillers like ibuprofen?

Regular use of NSAID painkillers with losartan can reduce its effect and harm the kidneys. Occasional use should still be discussed with your doctor or pharmacist, who may suggest a safer alternative.

4. Will losartan make me cough?

A persistent dry cough is mainly linked to ACE inhibitors (like enalapril). Losartan causes cough far less often and is frequently prescribed to people who could not tolerate an ACE inhibitor — but report any new persistent cough to your doctor.