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Losartan Potassium Uses & Side Effects

Losartan Potassium Pill Bottles

Losartan potassium is a prescription drug that is commonly used to treat high blood pressure. Please continue reading to learn some of the uses, side effects, warnings, and risks of taking this medicine.

What is losartan potassium used to treat? 

Losartan potassium is an angiotensin II receptor blocker (ARB). It is available as a low-cost generic drug and under the brand name Cozaar. A combination of losartan potassium and hydrochlorothiazide is available under the brand name Hyzaar.

Losartan is used by itself or with other blood pressure medicines to treat hypertension (high blood pressure). Other uses of losartan include to:

  • Decrease stroke risk in people with high blood pressure and left ventricular hypertrophy (a condition in which the walls of the left heart are enlarged). 
  • Slow the progression of diabetic nephropathy (kidney disease) in individuals with high blood pressure and type 2 diabetes.

In combination with other heart medications, losartan can be used off-label for the treatment of heart failure. 

Due to how losartan works, this medication is not the first choice to treat high blood pressure in African American patients. Renin is an enzyme secreted by the kidneys. Losartan and other angiotensin II receptor blockers (ARBs) are the most effective if high renin levels cause high blood pressure, and Black patients with high blood pressure usually have low renin. Therefore, losartan or other ARBs are not used as monotherapy for Black patients but rather as the second medication added when one medication does not provide adequate blood pressure-lowering effects or if the patient also has heart failure. This concept also applies to angiotensin-converting enzyme inhibitors (ACE inhibitors). Talk to your doctor or pharmacist if you have questions about your blood pressure medication regimen.                                                                               

How does losartan treat high blood pressure?

Losartan potassium and other angiotensin receptor blockers (ARBs) block the action of a natural substance called angiotensin II in the body. Angiotensin II tightens the blood vessels, and this hormone also increases salt and water retention in the body; both of these factors contribute to a rise in blood pressure. Therefore, by blocking the action of angiotensin II, taking losartan helps relax the blood vessels, improving blood flow and lowering blood pressure.  

How to take losartan?



Losartan is available as 25 mg, 50 mg, and 100 mg oral tablets. Losartan potassium tablet is dosed once daily. The usual starting dose for losartan in adults is 50 mg once a day and 25 mg if it is combined with a diuretic (water pill) like hydrochlorothiazide. Based on tolerability and the blood pressure response, losartan dose can be increased to 100 mg as needed for blood pressure control. The recommended maximum daily dose of losartan for adults is 100 mg daily  

Children 6 years and older

The dosage in children depends on the child’s body weight. It typically starts at 0.7 mg/kg of the child’s body weight and can go up to 50 mg once daily. The maximum dose of losartan is 1.4 mg/kg or 100 mg once daily. This medicine is not for children younger than 6 years or children who are at a certain level of kidney disease. 

People with liver problems

If you have mild to moderate liver disease, your doctor may start losartan at 25 mg once daily. 

Take as directed 

You can take the losartan oral tablet with or without food. Losartan oral tablets can be cut or crushed.

Losartan treatment works to lower blood pressure. As a result, the risk of stroke and heart disease is also reduced. Most people won’t be able to tell when their blood pressure is high until it becomes a medical emergency presenting symptoms such as severe headache, blurry vision, lightheadedness, and fatigue. Therefore, it is important that you continue to take losartan even if you are feeling well. It can take from 3 to 6 weeks for you to get the full effects of this medicine. 

Missed Dose

If you miss a dose of losartan, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and take the next dose at the scheduled time. Do not take extra medicine to make up for a missed dose.


Store losartan tablets in a cool, dry place away from moisture and heat, and safely out of reach of children and pets.

What are the negative side effects of Losartan?

Common side effects of losartan include back pain, leg pain, muscle cramps, stomach pain, diarrhea, fatigue, headache, sleep problems, and cold or flu symptoms such as sneezing, sore throat, fever, and stuffy nose. Call your doctor for medical advice about side effects if they are severe or do not go away within a few days.

More serious side effects of losartan treatment include a severe allergic reaction with swelling of the face, lips, tongue, throat, hives, and breathing difficulty. Seek emergency medical attention if this occurs. 

Other serious side effects that you should call your doctor immediately or call 911 if you feel like you are having a medical emergency include:

  • Kidney injury with symptoms include swelling in the feet, ankles, and hands, producing a lot less urine, and shortness of breath
  • High blood potassium levels with symptoms include muscle weakness, tingly feelings in arms and legs, weak pulse, and slow heart rate
  • Very low blood pressure where you are very lightheaded and feel like fainting
  • Rhabdomyolysis (muscle tissue breakdown) happens in very rare cases, leading to the breaking down of skeletal muscle, which can lead to kidney failure. Call your doctor immediately if you have unusual muscle pain and weakness, fatigue, fever, and dark urine.

In case of a losartan overdose, call the Poison Control Centers at 1-800-222-1222. If a person has collapsed, cannot be awakened, has had a seizure, or has trouble breathing, call 911. Signs and symptoms of a losartan overdose may include dizziness, very low blood pressure,  loss of consciousness, and a fast or slow heart rate.

What are losartan drug interactions?

Taking losartan with certain other medications can lead to potentially dangerous drug interactions. Give your doctor or pharmacist a complete list of your medications, including prescription drugs, over-the-counter medicines, dietary supplements, and herbal products to avoid dangerous adverse effects from a particular drug combination. Losartan has known interactions with the following other drugs:

What should I avoid while taking losartan?

Here are some dos and don'ts while taking losartan:


  • Eat a healthy, low-salt diet to help control your blood pressure. You may be able to come off losartan and other blood pressure medicines in the future if your blood pressure comes under control with lifestyle changes.
  • Losartan may not be right for everyone, such as people with heart failure, kidney problems (kidney disease or kidney failure), and liver problems. Give your doctor a complete medical history before starting losartan to avoid potential complications.
  • Take losartan exactly as your doctor prescribes. Do not take a higher or lower dose or take the medication more or less frequently than advised. Too much losartan can lead to serious adverse effects. 
  • Check your blood pressure at home and record the readings. Share them with your healthcare professional during appointments. This will help your provider see if losartan is working for you. 
  • Keep all your healthcare appointments during losartan therapy. Your healthcare provider may want to check your blood pressure and adjust your dose. They may order blood work including potassium levels and kidney function during treatment and adjust your losartan dose based on the results.
  • Losartan can cause low blood pressure when rising from a sitting or lying position, especially when you first start taking it or if you are dehydrated. Get up slowly from a sitting or lying position. Tell your doctor if you develop dizziness, lightheadedness, fainting, unusual tiredness, or confusion while on losartan.
  • Tell your doctor if you are pregnant or nursing an infant with breast milk. Talk to your doctor about effective birth control while on losartan. This medicine can cause serious birth defects or the death of an unborn baby if it is taken in the last 6 months of pregnancy.


  • Don’t change your dose of losartan suddenly or stop taking it without talking to your healthcare provider. Doing so can lead to a dangerous increase in your blood pressure. This medicine can reduce blood pressure, but it will not cure your condition. Continue taking losartan even if you feel well. Tell your doctor if you want to come off losartan - they will tell you how to lower your dose gradually.
  • Losartan can make you feel dizzy. Don’t drive, operate heavy machinery, or do anything that requires full concentration until you know how this medicine affects you. This side effect is usually worse when you first start taking losartan and when your dose is increased. It typically gets better as your body gets used to the medicine. 
  • Losartan can increase potassium levels in the blood. Don’t take potassium supplements or salt substitutes containing potassium unless your doctor says it is okay. Call your doctor if you develop nausea, vomiting, or muscle weakness - these can be signs of high potassium.

Note: This drug information is for general information purposes only. Your doctor or pharmacist can provide you with information that is specific to your diagnosis and personal health history.



  1. https://medlineplus.gov/druginfo/meds/a695008.html#:
  2. https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/020386s061lbl.pdf