Losartan, marketed under the brand name Cozaar, is taken with other drugs to help lower high blood pressure (hypertension).¹ It is available as an oral tablet and requires a prescription.

You can also access losartan as a generic medication. Generic medications are typically less expensive than their brand-name counterparts, but you might not be able to access them in every strength or form.

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What is losartan used to treat?

Losartan is used to treat the following conditions:

  • High blood pressure in adults and children

  • Diabetic nephropathy (a type of kidney disease induced by diabetes) in people who have or had type 2 diabetes and high blood pressure

  • Congestive heart failure

Losartan is also used to reduce the risk of stroke in people with hypertension and left ventricular hypertrophy (LVH), which occurs when the walls of the heart’s left ventricle thicken.

How do you take losartan?

Your doctor will prescribe a dose considering these factors:

  • The health condition being treated

  • Age

  • Weight

  • Other medical conditions (e.g., kidney damage)

Your doctor may prescribe a low dose to start with and gradually increase it until you are taking the right dose for you.

Always follow your doctor’s instructions when taking losartan — don’t take a higher dose than prescribed or take the drug more often.

Losartan tablets are usually taken in the following starting doses² when prescribed to treat high blood pressure:

  • Adults: 50mg once a day

  • Children aged six to 16: 0.7mg daily per kilogram of body weight

Seeing results

Losartan is an angiotensin II receptor antagonist (AIIRA) that works by preventing angiotensin II from binding to the angiotensin II receptor located in the muscles surrounding the blood vessels. Angiotensin II is a chemical that causes blood vessels to tighten when it binds to its receptor.

Taking losartan causes the blood vessels to dilate, lowering your blood pressure and enabling more blood and oxygen to flow to your organs.

Losartan can start to lower blood pressure after around two to six hours, but it may take a few weeks for you to notice its full effects.

Hypertension rarely causes symptoms, so you might only notice that losartan is working when you take a blood pressure reading.

Potential losartan side effects

Losartan may cause various adverse side effects, both moderate and severe.

The following is a list of some of the most common adverse side effects associated with losartan use:

  • Dizziness

  • Cough

  • Kidney problems

  • Elevated potassium levels

  • Stuffy nose

  • Back pain

  • Diarrhea

  • Fatigue

  • Low blood sugar

  • Chest pain

  • Low blood pressure

Talk to your doctor or pharmacist about any possible side effects you might develop when taking losartan. They may be able to give you some recommendations for avoiding or easing them.

Long-term losartan use

Losartan is generally safe to use for an extended time, but it does carry risks, including kidney damage. As a result, your doctor should order regular blood tests to assess your kidney function while taking losartan.

Missed doses

If you forget to take a dose of losartan, take it as soon as possible. Skip the missed dose if it’s nearly time to take the next one and then resume your usual dosing schedule. Do not take two doses to make up for the one you missed.

Losartan overdose

Signs of a losartan overdose² include:

  • Weakness

  • Dizziness

  • Pounding heart

If you think you or someone you know has taken an overdose of losartan, seek medical help straight away.

What to discuss with your doctor before taking losartan

Before you start taking losartan, inform your doctor about any prescription or over-the-counter medication you are currently taking. You should tell them about any vitamins, herbs, or supplements you use or plan to use.

Sharing this information helps prevent potentially harmful medication interactions.

Stopping losartan

Don’t stop taking losartan without consulting your doctor first. Abruptly stopping treatment can cause a rapid rise in blood pressure which significantly increases your chance of heart attack or stroke.

Talk to your doctor if you want to stop taking losartan. They will gradually decrease your dose until you can stop taking it without the risk of complications.

Losartan and pregnancy

Losartan should not be used during pregnancy³ as it can cause significant harm to a fetus. If you become pregnant while taking losartan, immediately stop taking the drug and contact your doctor.

Interactions with other drugs

Losartan can interact with a number of other drugs with several consequences. For example, some drugs can reduce losartan’s effectiveness, while others can raise your risk of experiencing adverse side effects.

Here is a list of medications that may interact with losartan:

  • Lithium

  • Certain blood pressure drugs

  • Nonsteroidal anti-inflammatory drugs (NSAIDs)

  • Rifampin

  • Diuretics (water pills)

  • Drugs or supplements that contain potassium

This list is not exhaustive, so you must tell your doctor about any medication you are currently taking to reduce the risk of potentially harmful interactions.

Allergy information

Seek medical assistance immediately if you develop any of the following symptoms of a severe allergic reaction:

  • Rash

  • Itching or swelling (particularly in the face, tongue, or throat)

  • Extreme dizziness

  • Trouble breathing

Clinical trial history

A countrywide, prospective, multicenter, observational trial⁴ of 29,850 participants evaluated losartan for effectiveness and safety.

Most participants took a daily dose of 25–50mg of losartan. The average follow-up time was 2.9 years. Before treatment, the participants’ mean systolic/diastolic blood pressure was 165.8/94.38mm Hg.

During the research period, losartan alone or in combination with other losartan-based drugs was found to effectively regulate blood pressure. Blood pressure in over half of the participants decreased to less than 140/90mm Hg.

In addition to lowering blood pressure, losartan was also found to lower uric acid and slow the development of proteinuria (protein in urine).

1,081 of the 29,850 participants experienced an adverse response to losartan.

Tips and advice for taking losartan

  • Take losartan with or without meals.

  • Hydrate yourself before taking losartan.

  • Your doctor may recommend taking losartan alongside other blood pressure-lowering medications (such as diuretics).

  • Losartan may cause your blood pressure to decrease rapidly, particularly after standing up from a seated or lying down position. This may cause dizziness and raise your risk of collapsing. Consult your doctor if this happens.

  • Talk to your doctor if you get swelling in your feet, ankles, or hands, or if you have unexplained weight gain. This might suggest your kidneys are not functioning properly.

  • Your doctor may recommend regular blood pressure, renal function, and electrolyte level checks while you take losartan.

  • Use appropriate contraception to avoid becoming pregnant while taking losartan as it can harm an unborn child. Inform your doctor immediately if you become pregnant while taking losartan.

  • Only take potassium supplements with losartan if your doctor has told you to.

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Here at HealthMatch, we’ve done our best to ensure that the information provided in this article is helpful, up to date, and, most importantly, accurate.

However, we can’t replace the one-to-one advice of a qualified medical practitioner or outline all of the possible risks associated with this particular drug and your circumstances.

It is therefore important for you to note that the information contained in this article does not constitute professional medical or healthcare advice, diagnosis or recommendation of treatment and is not intended to, nor should be used to, replace professional medical advice. This article may not always be up to date and is not exhaustive of all of the risks and considerations relevant to this particular drug. In no circumstances should this article be relied upon without independent consideration and confirmation by a qualified medical practitioner.

Your doctor will be able to explain all possible uses, dosages, precautions, interactions with other drugs, and other potential adverse effects, and you should always talk to them about any kind of medication you are taking, thinking about taking or wanting to stop taking.

Curious about clinical trials?

Access the latest treatments and medications. unavailable elsewhere - entirely free of charge. We make it easy to take part.