Medically Approved

How does losartan potassium treat high blood pressure?  

Man talking to doctor about high blood pressure

This powerful pill can lower your blood pressure without causing as many side effects as other medications. Learn what to expect if you start taking it. 

Hallie Levine

By Hallie Levine

Imagine you have a serious condition that has no symptoms — and as the years pass, it makes you much more likely to have a stroke or heart attack. What is this scary disease? High blood pressure, also known as hypertension.  

High blood pressure isn’t only scary. It’s common — nearly half of all adults in the U.S. have it. But it’s easily treated. There are many types of blood pressure medication out there. One of them is losartan potassium.  

“It’s part of a class of drugs known as angiotensin II receptor blockers (ARBs). It’s often used as a first-line treatment for high blood pressure,” explains Nieca Goldberg, MD. She’s the medical director at Atria New York City and a cardiologist at NYU Langone Health in New York.  

If your doctor suggests that you take losartan potassium (brand name Cozaar®), here’s what you need to know, from how it works to how you may feel.  

And if you’ve been given a losartan potassium prescription, don’t forget to bring this free prescription discount card with you to the pharmacy. It could save you up to 80% on your medications. 

How does losartan potassium work? 

Blood pressure is the force of blood as it pushes against the large veins leading to and from the heart. When your blood pressure is constantly high, those blood vessels can become less flexible over time. Losartan potassium works by blocking angiotensin. That’s a chemical in the body that causes blood vessels to narrow. Angiotensin itself needs a slot, or a receptor, to fit into to make the arteries tighten. Losartan potassium and other ARBs block those receptors so that they can’t narrow your blood vessels. As a result, your blood vessels stay open, and your blood pressure is lowered. 

Your doctor may recommend that you take losartan potassium if your blood pressure is consistently above 130/80, which is considered stage 1 hypertension. They may also prescribe it for other reasons, including: 

  • To lower the risk of a stroke in people who have high blood pressure and/or an enlarged heart. 
  • To treat kidney problems in people who have type 2 diabetes and high blood pressure.  

How to take losartan potassium 

It comes in tablets that you swallow. Usually, you take it once or twice a day. If you take it once a day, try taking it at night.

Your doctor will probably start you on a low dose, usually 50 milligrams (mg) a day. Then they’ll gradually raise the dose as needed. The maximum daily dose you can take is 100 mg.  

Your blood pressure should go down during the first week that you take it. But it may take up to 6 weeks for you to see the full benefits.  

If your blood pressure doesn’t reach the target level (usually 120/80 or under), your doctor may increase your dose and/or add a second medication, notes Dr. Goldberg. Or they may prescribe a different blood pressure medication altogether. “Losartan potassium is one of the weaker ARBs. So if a patient doesn’t respond, we may try another ARB,” she says.  

Recommended reading: The Optum Perks guide to blood pressure medications

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How does losartan potassium compare to other blood pressure medications?  

Doctors often recommend that patients try losartan potassium first. It not only works well but also has few side effects, says Michael Hochman, MD. He’s a Los Angeles-based internist and the host of the podcast The Healthy Skeptic.  

Research backs that up. A study published in Hypertension found that ARBs work just as well as another common type of blood pressure medication called an ACE inhibitor. Both do a great job of lowering the odds of a heart attack or stroke. But ARBs tended to do better at minimizing certain side effects. In fact, people who took ARBs were:  

  • 3.3 times less likely to develop swelling from extra fluids trapped in the deep layers of the skin 
  • 32% less likely to develop a chronic cough 
  • 32% less likely to develop inflammation of the pancreas 
  • 18% less likely to develop bleeding in their gastrointestinal tract 

(Be sure to download our free mobile app to find the best price on your medications at a pharmacy near you.) 

What are losartan potassium’s side effects? 

Losartan potassium doesn’t cause as many side effects as other blood pressure medications. But there may still be some. The most common ones include: 

  • Knee or back pain 
  • Muscle cramps or weakness 
  • Diarrhea 
  • Heartburn 
  • Being less sensitive to touch 

Your doctor will also want you to get a blood test occasionally to check your electrolyte levels, says Dr. Goldberg. “Sometimes ARBs can increase your potassium levels or lower your sodium levels, so we watch that,” she explains.  

Those levels tend to rise and fall when you take losartan potassium with a diuretic, Dr. Goldberg says. Diuretics are another type of blood pressure medication that works on your kidneys. But you can stop the fluctuations by adjusting the losartan potassium dosage.  

You might need to get blood tests more often if you have kidney disease, says Dr. Hochman. That way, doctors can keep an eye on it. “While losartan potassium does protect the kidneys, it can also push kidneys over the edge,” he explains. “We always want to be careful.”  

Can losartan potassium cure my high blood pressure?  

Losartan works well, but it’s not a magic pill. And no medication “cures” high blood pressure. Doctors recommend that you also make the following little changes to lower it even more.  

  • Lose some weight. With every 2.2 pounds you lose, your blood pressure may go down by about 1 mm Hg. 
  • Eat less salt. It can lower blood pressure by about 5 to 6 mm Hg. 
  • Go for a heart-healthy diet. Eating more fruits, veggies, whole grains and low-fat dairy products can reduce your blood pressure by up to 11 mm Hg.  
  • Move more. Walking, dancing or bicycling a few times a week can lower your blood pressure by up to 8 mm Hg. 

No matter how you manage your blood pressure, Optum Perks wants to help you save at the pharmacy. Here’s how it works


Additional sources:  
Blood pressure stats: American Heart Association  
ARBs vs. ACE inhibitors: American Heart Association
Best time to take losartan potassium: European Heart Journal (2019). “Bedtime hypertension treatment improves cardiovascular risk reduction: the Hygia Chronotherapy Trial”