Learn About Losartan Side Effects to Manage Hypertension Safely

Learn About Losartan Side Effects To Manage Hypertension Safely

Blood pressure is the force exerted by the blood against the walls of the blood vessel. If this pressure is higher than 130/80 mmHg per the American Heart Association guidelines, it is called high blood pressure (hypertension). Nearly half of American adults suffer from hypertension, and many are unaware of their condition. (1-2)

High blood pressure can damage the circulatory system over time, so regulating it is crucial. Hypertension is a risk factor for heart attacks and stroke, some of the leading causes of death in the U.S. Yet, only about one in four adults with hypertension has their blood pressure well controlled. (1-2)

Losartan is a prescription medicine used to manage hypertension alone or in combination with other blood pressure drugs. It has been shown to be a well-tolerated medication, but it still has possible side effects that each patient should know. (3)

If your doctor has prescribed losartan, this article will help you to learn about common and serious side effects. Keep reading to find out in which situations you need to call your doctor immediately.

Losartan Relaxes Blood Vessels And Lowers The Pressure

Before going into details about losartan’s side effects, it is helpful to understand how it works and the other health conditions which losartan can be used for.

Losartan belongs to a group of medications called angiotensin II receptor blockers (ARBs). ARBs block angiotensin II receptors in the body, preventing its function. Angiotensin II is a substance that tightens blood vessels, increasing blood pressure. As a result, losartan relaxes blood vessels; allowing blood to flow more easily. (4)

This mechanism makes losartan effective against other diseases, such as:

  • Lowering the chances of strokes in patients with high blood pressure and a heart problem called left ventricular hypertrophy (LVH). LVH is an enlargement of the heart’s left chamber muscle/walls, which is the main pumping chamber. High blood pressure is the most common cause of LVH. You should know that losartan may not decrease the risk of stroke in African Americans with these conditions. (3-4)
  • Slow the worsening of diabetic kidney disease (nephropathy) in people with type 2 diabetes who have or had high blood pressure before. Type 2 diabetes happens mainly in adults and can damage the kidney, so the kidney will not work properly. (3-4)

Losartan’s Possible Side Effects

People with high blood pressure need medical treatment to regulate the pressure, and losartan can be an option. Losartan is generally well tolerated and has been in use since 1995. In the initial clinical trials, only 2.3% of the patients discontinued the treatment with losartan due to side effects. (3)

Common Side Effects

However, there are side effects that people with high blood pressure using losartan may experience. The most common side effects with an incidence of over 2 in 100 patients are: (3, 5)

Losartan Side Effects

Losartan Side Effects – Common side effects

  • “Colds” (upper respiratory infection);
  • Dizziness;
  • Stuffy nose;
  • Back pain;
  • Leg pain;
  • Muscle cramps;
  • Sinusitis.

It is good to mention that the incidence of these side effects in the treatment group was similar to that of the subjects on placebo (not taking losartan), indicating that these were not “true” side effects due to losartan. (3)

You may feel dizzy after the first dose. It could happen when you take losartan, particularly with a diuretic. If you experience dizziness, lie down for a while, then sit and wait to feel better. You should avoid driving and operating machinery. (6)

People with type 2 diabetes and diabetic kidney disease may have the following most common side effects of losartan:

  • Diarrhea;
  • Anemia;
  • Urinary tract infections;
  • Cough;
  • Respiratory tract infections;
  • Tiredness;
  • Cellulitis;
  • Muscular weakness;
  • Knee pain;
  • Leg pain;
  • Low blood sugar;
  • Chest pain;
  • High blood potassium;
  • Low blood pressure. (3, 5)

You might have heard about a persistent dry cough associated with other high blood pressure medications (Angiotensin-converting enzyme inhibitors such as enalapril, lisinopril, captopril, and many more). Two double-blind controlled clinical trials assessed the losartan’s effect on the incidence of the cough. Patients previously treated with lisinopril who had the cough were switched to losartan for eight weeks. The incidence of cough in the losartan group was lower than in the Lisinopril group and was comparable to that in the placebo or hydrochlorothiazide group. (3)

Serious Side Effects

Tell Your Doctor If You Get Any Of The Following Side Effects: (3)

  • Allergic reaction – if you experience swelling of the face, lips, throat, or tongue, it can be due to an allergic reaction or angioedema. If this happens, you should stop taking the medication and get emergency medical attention right away.
  • Low blood pressure – if you feel faint or dizzy, it could be a symptom of hypotension. If you feel so, lie down and call your doctor immediately.
  • Worsening of the kidneys happens in people who already have kidney problems – in such cases, you may have swelling in your feet, ankles, or hands or gain weight unexpectedly due to water retention.
  • High blood levels of potassium frequently cause heart rhythm problems, muscle weakness, chest pain, nausea, vomiting, or diarrhea. (3, 7)
  • Muscle pain and weakness and darkened urine, usually tea-colored, are symptoms of rhabdomyolysis. This condition is due to the breakdown of muscle cells and could be a severe side effect of losartan, requiring immediate medical attention.
  • Low platelet count can be seen in people taking losartan. It can be asymptomatic or produce nose or gums bleeding and/or purple spots on the skin. Visit your doctor if you see the above manifestations.
  • Hepatitis is another reported severe side effect of losartan. It may manifest with yellow-colored skin and the white part of the eye (jaundice), stomach pain, fatigue, and darkened urine. This condition requires prompt medical attention.

You may find out about side effects in the patient information inserted in the losartan pack. (3) Ask your doctor or pharmacist for a complete list of side effects.

Warning And Precautions

Fetal toxicity – The major warning that the Food and Drug Administration has issued to losartan is fetal toxicity. Drugs that act on the renin-angiotensin system during the second and third trimesters of pregnancy reduce fetal renal function and increase fetal and neonatal morbidity and death. You can find the warning in the patient information:

“When pregnancy is detected, discontinue losartan as soon as possible. Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus.” (3)

Hypotension may occur after the beginning of losartan treatment in patients who use high doses of diuretics. It results from depleted salt and liquid volume. In this case, the doctor will correct volume or salt depletion before losartan treatment begins. (3)

Renal function and potassium levels monitoring – Losartan and diuretics may change renal function, including acute renal injury, or cause hyperkalemia (higher than normal potassium levels). Therefore, your doctor will monitor renal function and potassium levels. (3)

Patients with renal artery stenosis, chronic kidney disease, severe congestive heart failure, or volume depletion are at risk of developing acute renal failure if using losartan. If you are one of this group of patients, regularly visit your doctor to monitor renal function. The doctor might discontinue losartan if a significant decrease in renal function is identified. (3)

If you experience a serious side effect, you or your doctor can report it to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (https://www.fda.gov/safety/medwatch-fda-safety-information-and-adverse-event-reporting-program) or by phone (1-800-332-1088). (8)

Dosage And Administration

Losartan is available in tablets with a strength of 25 mg, 50 mg, and 100 mg.

For hypertension treatment patients with hypertension, left ventricular hypertrophy, and diabetes nephropathy, the usual adult starting dose is 50 mg once daily. The dose can be increased to 100 mg daily.

In patients with hypertension and left ventricular hypertrophy, losartan can be administered in combination with the diuretic hydrochlorothiazide, which helps the body to get rid of extra salt and water.

In the pediatric population older than six years, the starting dose is 0.7 mg per kg once daily (up to 50 mg).

If you take losartan more than needed, it could lead to hypotension and tachycardia. Dizziness, fainting, or a fast or slow heartbeat are overdose symptoms. In some cases of overdose, supportive treatment might be necessary. Therefore, call the poison control helpline at 1-800-222-1222. You may find available information online at https://www.poisonhelp.org/help. (3, 8)

What You Should Tell Your Doctor Before Taking Losartan

Before you start taking losartan, tell your doctor about all of your medical conditions, including:

  • Pregnancy or planning to become pregnant as explained before;
  • Breastfeeding – it is unknown whether losartan passes into your breast milk. Therefore, losartan should not be used, or the mother should stop breastfeeding;
  • Excessive vomiting or diarrhea;
  • Having liver problems;
  • Having kidney problems;

Remember to mention all the medication, supplements, and vitamins you take due to possible interaction with losartan or dual activity on blood pressure reduction. (3)

Hypertension management requires blood pressure monitoring and lifestyle changes. Once you get high blood pressure, it cannot be cured, but you can certainly control it. Regular medical treatment plays an important role; sometimes, it takes time to find the appropriate drug or combination of drugs that works for you.

High blood pressure monitoring at home will give your doctor feedback on how the medication(s) work. Regular and proper use of a home blood pressure monitor will tell you if your pressure is in the normal range, elevated, or high. Learn how to measure properly; here are some useful tips:

  • No cigarettes, caffeinated drinks, or exercise 30 minutes before measurements;
  • Sitting down for at least 5 minutes before measurements;
  • Sit with a straight back and flat feet on the floor during measurements;
  • Put your arm on a flat surface and your upper arm at the heart level;
  • Don’t measure your blood pressure over clothes;
  • Measure daily at the same time at least two to three times, or as your doctor advised you;
  • Write the results in a tracker. (2)

This lifetime blood pressure management means making changes that will contribute to the best results. American Heart Association recommends the following:

  • Decrease salt and salty food;
  • Introduce a heart-healthy diet rich in vegetables, fruits, whole grains, fish, nuts, legumes, and other healthy food;
  • Limit food rich in saturated fats, red meat, sweets, and sweetened beverages;
  • Be physically active for at least 150 minutes weekly, with activities that you like;
  • Learn to manage stress;
  • Keep your weight healthy;
  • Quit smoking. (2)

The list looks long; however, making these lifestyle changes can lower your risk of heart attack, stroke, kidney damage, and other health complications.


High blood pressure is a disease that requires medical treatment. Hypertension cannot be cured, but the pressure needs to be regulated to prevent stroke or heart attack. Take losartan and other high blood pressure medication as your doctor prescribed, and be aware of your condition.

Read the patient information carefully and get familiar with all possible side effects. If you experience any adverse event, talk to your doctor. If you are pregnant or plan to be, talk to your doctor before starting losartan treatment. In case of serious side effects, call your doctor or emergency immediately.

Visit your doctor regularly and follow instructions for medical checks and monitoring of specific parameters even when you feel better. Your doctor and the medication you use can do a lot; you can do even more to get you to feel better.

See Also

Amoxicillin Side Effects

Amlodipine Side Effects

Sertraline Side Effects

Doxycycline Side Effects

Lisinopril Side Effects

Lexapro Side Effects

  1. CDC Centers for Disease Control and Prevention, Facts About Hypertension, 2023 Jan, https://www.cdc.gov/bloodpressure/facts.htm
  2. American Heart Association, The Facts About High Blood Pressure, 2017 Nov, https://www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure
  3. FDA Food and drug administration, COZAAR® (losartan potassium) tablets, for oral use, 2018 Oct, https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/020386s062lbl.pdf
  4. NIH National Library of Medicine, Losartan, Sana Mulla; Waqas J. Siddiqui., 2022 Jul, https://www.ncbi.nlm.nih.gov/books/NBK526065/
  5. Losartan – AMBOSS [Internet]. [cited 2023 Jul 22]. Available from: https://next.amboss.com/us/pharma/losartan?q=losartan
  6. Mayo Clinic, Losartan (Oral Route), 2023 Jan, https://www.mayoclinic.org/drugs-supplements/losartan-oral-route/side-effects/drg-20067341?p=1
  7. Cleveland Clinic, Hyperkalemia (High Potassium), 2020 Oct, https://my.clevelandclinic.org/health/diseases/15184-hyperkalemia-high-blood-potassium
  8. MedlinePlus, Losartan, 2018 Feb, https://medlineplus.gov/druginfo/meds/a695008.html

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