What is Losartan: Uses, Warnings & Interactions

Updated May 14, 2025  •  Published Dec 30, 2020

Losartan is a generic blood pressure medication primarily prescribed to people with high blood pressure. As a medicine that lowers blood pressure, it also has more specialized uses in people with an enlarged heart or kidney damage. Losartan has few side effects, but it can seriously harm a fetus, so it’s never given to pregnant women.

Losartan overview

BRAND NAMES:

  • Cozaar

Generic Names:

  • Losartan potassium

Uses:

  • Treats high blood pressure, reduces the risk of stroke in patients with high blood pressure and an enlarged heart, and treats kidney disease in patients with diabetes

Therapeutic Classes:

  • Angiotensin II receptor blocker (ARB), antihypertensive, cardiovascular agent, renal protective agent

Forms:

  • Tablet

How it’s taken:

  • By mouth

What is Losartan used for?

Losartan lowers blood pressure. Doctors primarily use losartan to lower blood pressure in adults and children older than 6 years old who have high blood pressure. Doctors also use it to reduce the risk of stroke in people with both high blood pressure and an enlarged chamber of their heart, a condition called left ventricular hypertrophy or LVH. Finally, losartan is prescribed to treat kidney damage in people with Type 2 diabetes and a history of high blood pressure.

What form(s) does Losartan come in

  • Tablet

    • 25 mg

    • 50 mg

    • 100 mg

What are common Losartan doses?

  • For high blood pressure in adults: 50–100 mg taken once per day or in two divided doses

  • For high blood pressure in children 6 years of age or older: 0.7 mg/kg taken per day up to a maximum of 50 mg

  • For stroke prevention in people with an enlarged heart and high blood pressure: 50–100 mg taken once per day

  • For diabetic nephropathy (kidney damage) in people with Type 2 diabetes and a history of high blood pressure: 50–100 mg taken once per day

RELATED: Cozaar dosage, forms, and strengths

Common Losartan prescriptions

  • Losartan Potassium
    30 tablets bottle

  • Losartan Potassium
    90 tablets bottle

  • Losartan Potassium
    30 tablets disp pack

  • Losartan Potassium
    100mg tablet

  • Losartan Potassium
    25mg tablet

  • Losartan Potassium
    50mg tablet

How to take Losartan

  • Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.

  • Losartan tablets can be taken with or without food.

  • Swallow losartan tablets with a drink of water.

  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

  • Store the medicine in a closed container at room temperature protected from light and out of the reach of children.

What to do if you miss a dose of Losartan

  • Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. 

  • Do not take extra medicine to make up for a missed dose.

Losartan contraindications

  • This medicine is not right for everyone. 

  • Do not take losartan if you are pregnant. Losartan can harm an unborn baby.

  • Do not use this medicine if you have had an allergic reaction to losartan.

  • If you have diabetes, do not use this medicine together with the blood pressure medication Tekturna (aliskiren).

Losartan warnings

  • It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant.

  • Tell any doctor or other healthcare provider who treats you that you are using this medicine.

  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.

  • Tell your doctor if have:

    • Plans to become pregnant

    • Kidney disease

    • Liver disease

    • Congestive heart failure

    • Diabetes

    • Have had an allergic reaction involving facial swelling and similar symptoms caused by another blood pressure drug.

  • Tell your doctor if you are breastfeeding or plan to breastfeed.

  • This medicine could lower your blood pressure too much, especially when you first use it or if you are dehydrated, salt-depleted, or using other blood pressure medications. Stand or sit up slowly if you feel lightheaded or dizzy.

  • When taking losartan, drink plenty of fluids if you exercise, sweat more than usual, or have diarrhea or vomiting.

Losartan interactions

  • To avoid potentially hazardous drug interactions, tell the prescribing healthcare provider about all prescription drugs, over-the-counter medicines, and supplements you are using before taking losartan.

  • Tell other healthcare providers you are using this medicine before they prescribe new medications.

  • Some medicines can affect how losartan works or worsen possible side effects. Tell your doctor if you are using any of the following: 

  • Ask your doctor before you use any medicine, supplement, or salt substitute that contains potassium.

  • Find out more about losartan interactions to avoid here.

Losartan side effects

Serious side effects

Talk to a doctor if you notice any signs or symptoms of a possible serious side effect, including:

  • Change in how much or how often you urinate, rapid weight gain, swelling in your hands, ankles, or feet

  • Lightheadedness, dizziness, fainting

  • Confusion, weakness, uneven heartbeat, trouble breathing, numbness or tingling in your hands, feet, or lips

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing

Losartan can cause serious side effects that may not have symptoms including:

  • Injury or death of an unborn baby

  • High potassium

Less serious side effects

  • Upper respiratory infections like colds

  • Dizziness

  • Stuffy nose

  • Back pain

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