Losartan side effects and how to avoid them

In this article:

• Common side effects
• Serious side effects
• Does losartan cause weight gain?
• Side effects of losartan by dose
• How soon do side effects start?
• How long do side effects last?
• What are the long-term side effects of losartan?
• Losartan interactions
• Safety measures while using losartan
• How to avoid side effects
• How to treat side effects

In this article

• Common side effects
• Serious side effects
• Does losartan cause weight gain?
• Side effects of losartan by dose
• How soon do side effects start?
• How long do side effects last?
• What are the long-term side effects of losartan?
• Losartan interactions
• Safety measures while using losartan
• How to avoid side effects
• How to treat side effects

Losartan potassium (generic Cozaar) is a prescription angiotensin II receptor blocker (ARB) used to treat hypertension (high blood pressure), reduce the risk of stroke, and prevent diabetes-related kidney disease. It’s sometimes used off-label to treat heart failure or non-diabetic kidney problems. It relaxes blood vessels, allowing blood to flow more easily.

Losartan is generally well-tolerated and may be better tolerated than ACE inhibitor blood pressure medications. Still, side effects can occur. Knowing what to watch for can help you respond early and seek medical care when needed.

Common side effects of losartan

According to the FDA drug label, the most common side effects of losartan include dizziness and upper respiratory infection (such as the common cold). In clinical trials, about 8% of people taking losartan developed a cold, compared with 7% of those taking a placebo. 

The most commonly reported side effects include:

• Dizziness 
• Upper respiratory infection
• Nasal congestion
• Back pain 

People taking losartan for diabetic nephropathy also experience:

• Fatigue or weakness
• Low blood pressure
• High potassium levels
• Chest pain

Serious side effects of losartan

Although less common, losartan can cause serious side effects that require prompt medical attention. These include:

• Severely low blood pressure
• High potassium levels (hyperkalemia)
• Kidney problems or failure
• Irregular heartbeats (arrhythmias)
• Liver disease
• Severe allergic reaction, including trouble breathing and/or swelling of the face and throat)

Does losartan cause weight gain?

Weight gain is not listed as a side effect of losartan in the drug label. In fact, some post-market research suggests that losartan may be associated with weight loss in certain patients. 

There are a few possible explanations for this. Some studies suggest losartan may improve insulin sensitivity, which can play a role in weight regulation. Other research indicates it may affect leptin signaling, a hormone involved in appetite and cravings. However, these findings are largely based on animal studies and limited data.

Overall, there’s no strong evidence that losartan causes weight gain. While some people may experience weight loss, this effect is not common or guaranteed. 

Side effects of losartan by dose

The typical losartan dosage ranges from 50-100 milligrams (mg) per day. It is taken orally as losartan film-coated tablets in strengths of 25 mg, 50 mg, and 100 mg.

A study published in the American Heart Association Journals compared side effects across different doses of losartan (an ARB), enalapril (an ACE inhibitor), and a placebo. While side effects varied slightly between doses, researchers concluded that these differences were not clinically significant.

Can you overdose on losartan?

Yes, as with any prescription medication, taking too much losartan is a medical emergency. The typical maximum dose is 100 milligrams (mg) per day. 

Contact a poison control center or a healthcare provider right away if an overdose is suspected. Symptoms may include low blood pressure and changes in heart rate, such as a fast or slow heartbeat.

How soon do losartan side effects start?

Losartan starts working soon after the first dose, and common side effects may develop within the first few days to weeks of treatment, according to JaLorean Hayes, MPH, BSN, a registered nurse, public health advocate, and founder of Meal Maps. 

Symptoms of severe allergic reaction to losartan, such as hives, shortness of breath, or swelling of the face or tongue, may occur within minutes to hours after taking the first dose.

How long do losartan side effects last?

According to the drug label, it takes about two hours for the body to eliminate half a dose of losartan. Because of this, some side effects may begin to improve within a few hours to a couple of days after stopping the medication.

However, the duration of the side effects depends on the severity of what you experience. Mild side effects, such as nasal congestion and back pain, don’t last long, according to Cynthia Odogwu, MD, a family and lifestyle medicine physician in Maryland. 

In rare cases, a serious side effect such as kidney failure may take more time and additional treatment to resolve. 

What are the long-term side effects of losartan?

Losartan is generally considered safe and effective for long-term use. The drug label does not list specific long-term side effects. That said, rare but serious effects, such as a decline in kidney function, may have lasting consequences. People with existing kidney conditions may be at higher risk. Regular monitoring, such as routing blood work and kidney function tests, is recommended while taking losartan.

Losartan interactions

Losartan is generally a well-tolerated drug, but the risk of adverse reactions increases when taking multiple medications. Drug interactions to avoid include:

• Potassium-raising agents: Potassium-sparing diuretics, potassium supplements, or potassium-rich foods can raise potassium levels too high when combined with losartan. This includes common concerns around losartan and bananas, since bananas are high in potassium and may contribute to elevated levels (hyperkalemia).
• Nonsteroidal antiinflammatory drugs: NSAIDs such as ibuprofen or naproxen can increase the risk of kidney damage when used with losartan.
• Other drugs that block the renin-angiotensin hormone system: Combining losartan with ACE inhibitors or other ARBs can intensify the risk of kidney problems.
• Other blood pressure drugs: Losartan widens blood vessels to lower blood pressure. Combining it with other blood pressure-lowering drugs can result in dangerously low blood pressure.

In patients with diabetes, losartan is also contraindicated. This means it should not be mixed with Tekturna (aliskiren).

Safety measures while using losartan

Losartan is a well-tolerated drug. It is not habit-forming, and only a small number of recalls have been reported. However, it may not be safe for everyone. 

Who should not take losartan?

According to the drug label, losartan is not recommended for:

• People who are pregnant: Losartan can cause serious harm to a fetus and may lead to fetal death. The FDA has issued a black box warning advising that the drug should be discontinued as soon as pregnancy is detected.
• Children younger than 6 years old: Losartan is not approved for use in very young children. It is also contraindicated in pediatric patients with severe kidney disease. 
• Breastfeeding mothers: It’s not known whether losartan passes into breast milk. Other blood pressure drugs may be preferred while breastfeeding. 
• People with an allergy to any of the medication’s components

Who should use caution when taking losartan?

The FDA also advises caution in people with:

• Kidney disease or impairment
• Dehydration
• Low sodium
• Liver disease
• Severe congestive heart failure

Losartan may affect kidney function and blood pressure levels, so monitoring is important in these groups.

Older adults are not restricted from using losartan, but they may be more sensitive to its blood pressure–lowering effects and should be monitored closely.

Some studies suggest that ARBs, including losartan, may be less effective in lowering blood pressure in Black patients. Treatment response can vary, so a healthcare provider may adjust therapy based on individual needs.

How to avoid losartan side effects

Losartan has few side effects, but there are practical ways to reduce the risk or minimize symptoms while taking this medication.

1. Take losartan as instructed

Losartan is available in multiple strengths. Take only the dose prescribed by your healthcare provider.

It is typically taken once or twice daily. If you miss a dose, take it as soon as you remember unless it’s almost time for your next dose. In that case, skip the missed dose. Do not take two doses at the same time.

2. Stay hydrated

Proper hydration helps maintain stable blood pressure and may reduce the risk of dizziness.

People taking diuretics (water pills) or laxatives should be especially mindful of fluid intake, as these can increase the risk of dehydration.

3. Limit alcohol

Losartan can cause dizziness, which may worsen with alcohol consumption. Alcohol may also interfere with blood pressure control. Limiting or avoiding alcohol is generally recommended while taking losartan.

4. Monitor potassium intake

Though losartan can be taken with or without food, according to Hayes, it’s important to pay attention to your overall diet while on losartan, particularly potassium intake.

“Foods high in potassium or potassium supplements can increase the risk of too much potassium in the body,” Hayes says. “Some salt substitutes also have potassium chloride, which can contribute to developing hyperkalemia as well.”

RELATED: What causes high potassium?

5. Take losartan at the same time each day.

There is no specific “best” time of day to take losartan, but consistency is important. Dr. Odogwu suggests finding a time that is comfortable for you. 

“It is important to take it at the same time each day, so that it is in your system for 24 hours,” she adds. “My patients are more likely to remember to take their Losartan if they stick to taking it at the same time, every day.”

How to treat the side effects of losartan

Many common side effects can be treated at home as your body adjusts to the medication. However, seek medical attention right away if you experience signs of a serious reaction, such as:

• Allergic reaction (hives, swelling of the face or throat, trouble breathing)
• High potassium (weakness, nausea, tingling)
• Kidney problems (changes in urination, swelling, or unexplained weight gain)

For milder side effects, the following strategies may help:

• Dizziness: Move slowly when standing up or sitting down. Sit or lie down until symptoms pass.
• Upper respiratory infection: Rest and stay hydrated.
• Nasal congestion: Ask a healthcare provider about appropriate over-the-counter (OTC) options. Using a humidifier or taking steamy showers may also help.
• Back pain: Ask your provider about OTC pain relief. Gentle stretching, heat therapy, or massage may provide relief.

Bottom line: Is losartan safe?

Yes, Losartan is generally considered safe for people with the conditions it is prescribed to treat: 

• Hypertension (high blood pressure)
• Nephropathy in people with Type 2 diabetes
• Stroke risk reduction
• Heart disease (off-label use)

Because losartan is a prescription medication, it should only be used under the guidance of a healthcare provider. Do not start, stop, or change your dose without medical advice.