Overview: Losartan is used for high blood pressure or in certain people with high blood pressure or diabetes. Common side effects may include dizziness, stuffy nose, or back pain. Do not drive or. Losartan, sold under the brand name Cozaar among others, is a medication used to treat high blood pressure (hypertension). [4] It is in the angiotensin receptor blocker (ARB) family of medication, and is considered protective of the kidneys. Learn about the side effects of losartan, from common to rare, for consumers and healthcare professionals. Losartan is a safe, effective and widely prescribed blood pressure medication that offers real benefits for heart health. While it does come with one key potential side effect—elevated potassium levels—this can actually work in your favor depending on your individual health needs. Losartan is used to treat high blood pressure and to help protect the kidneys from damage due to diabetes. Learn about side effects, drug interactions, dosages, warnings, and more. Losartan is a prescription drug to treat high blood pressure, diabetic nephropathy, and stroke risk. Learn about side effects, warnings, dosage, and more. Losartan is used to treat high blood pressure (hypertension). It is also used to lower the risk of stroke in certain people with heart disease. Losartan (Cozaar) is an angiotensin II receptor blocker (ARB) commonly prescribed to treat high blood pressure. Common losartan side effects include dizziness, respiratory infections, and back or joint pain. Fatigue, headache, and digestive issues are also possible. NHS information about the medicine losartan, including what it's used for, who can use it, how to use it and side effects. Losartan is an angiotensin II receptor blocker (ARB). It works by blocking a substance in the body that causes blood vessels to tighten. As a result, losartan relaxes the blood vessels. A lower blood pressure will increase the supply of the blood and oxygen to the heart.