What is the most common side effect of losartan? An expert guide to managing side effects

October 10, 2025 •

4 min read

According to clinical trial data, dizziness is the most commonly reported side effect of losartan, affecting a small but notable percentage of patients. This mild but bothersome effect is often associated with a drop in blood pressure and can be more pronounced when first starting the medication or increasing the dose.

Quick Summary

Dizziness is the most frequently reported side effect of losartan, often occurring as the body adjusts to the medication's blood pressure-lowering effects. Other common, mild side effects include upper respiratory infections and nasal congestion, while more serious issues like high potassium are less frequent. Symptoms can usually be managed with simple strategies.

Key Points

Dizziness is the most common side effect: It is often reported, especially when treatment begins or the dose is changed, but usually subsides as the body adjusts.
Dizziness is linked to blood pressure changes: It is a result of the medication effectively lowering blood pressure, which can cause lightheadedness when standing up quickly.
Other common side effects include respiratory issues: Upper respiratory infections, nasal congestion, and back pain are also frequently reported side effects.
Losartan is an alternative to ACE inhibitors for cough: It has a significantly lower incidence of persistent cough compared to medications like lisinopril.
Serious but rare side effects exist: High blood potassium (hyperkalemia) and allergic reactions (angioedema) are possible and require immediate medical attention.
Management strategies are effective: Rising slowly, staying hydrated, and avoiding alcohol can help manage dizziness.
Open communication with a doctor is essential: It is crucial to report all side effects to your healthcare provider for proper management and dosage adjustment.

Understanding Losartan: How it Works and Why Side Effects Occur

Losartan, also known by its brand name Cozaar, is an angiotensin II receptor blocker (ARB) used primarily to treat high blood pressure (hypertension). It also helps reduce the risk of stroke in certain patients and can treat kidney disease in people with type 2 diabetes and high blood pressure. The medication works by blocking the action of angiotensin II, a chemical that narrows blood vessels. By preventing this action, losartan causes blood vessels to relax and widen, which in turn lowers blood pressure.

This mechanism is also the root cause of the most common side effect of losartan: dizziness. As the medication effectively lowers blood pressure, a person's body may need time to adjust. A rapid or significant drop in blood pressure can lead to lightheadedness, which is why dizziness is frequently reported, especially during the initial stages of treatment or after a dosage adjustment.

The Most Common Side Effect: Dizziness

Dizziness is the most prevalent side effect of losartan, affecting some individuals more than others. This symptom is often a form of orthostatic hypotension, which is a drop in blood pressure that occurs when a person stands up quickly from a sitting or lying position. For most people, this sensation is mild and temporary, resolving as the body adapts to the new blood pressure level.

How to manage dizziness:

Rise slowly: To minimize lightheadedness, it is recommended to get up slowly from a seated or lying position.
Stay hydrated: Dehydration can exacerbate low blood pressure. Drinking plenty of fluids can help maintain blood pressure and reduce dizziness.
Avoid alcohol: Alcohol can intensify the blood pressure-lowering effect of losartan, increasing the risk of dizziness.
Report persistent symptoms: If dizziness is severe or does not go away after the initial adjustment period, it is important to inform a healthcare provider. The dosage may need to be adjusted.

Other Frequently Reported Side Effects

While dizziness may be the most common, several other side effects are often reported during losartan treatment. These are typically mild and often improve over time. A number of studies indicate a higher incidence of upper respiratory tract infections in patients taking losartan compared to placebo.

Other common mild side effects include:

Upper respiratory tract infections: Symptoms similar to the common cold, such as a stuffy or runny nose, a sore throat, and sneezing, are common.
Back pain: Some patients experience mild to moderate back pain while on losartan. The exact reason for this is not fully understood.
Fatigue: A general feeling of tiredness or weakness can be a side effect.
Cough: Although significantly less common than with ACE inhibitors, a persistent dry cough can occur in some individuals taking losartan.

Comparison of Losartan and ACE Inhibitor Side Effects

Losartan is frequently prescribed to patients who cannot tolerate ACE inhibitors, a similar class of blood pressure medication, due to side effects like a persistent, dry cough. This difference is a key reason for switching medications.

Losartan vs. ACE Inhibitors: A Comparison of Common Side Effects


Side Effect	Losartan	ACE Inhibitors (e.g., Lisinopril)
Cough	Significantly lower incidence, similar to placebo	High incidence of persistent dry cough
Dizziness	Common, especially initially; milder in comparison	Also common due to blood pressure reduction
Angioedema	Rare risk, but occurs	Higher, but still rare, risk

Serious but Less Common Side Effects

It is important to be aware of potentially serious side effects, even if they are rare. These require immediate medical attention.

High potassium levels (Hyperkalemia): Losartan can cause an increase in blood potassium levels, especially in patients with pre-existing kidney disease or those taking potassium-sparing diuretics. Symptoms of hyperkalemia include muscle weakness, fatigue, an irregular heartbeat, or chest pain.
Kidney problems: Losartan may impact kidney function, particularly in individuals with pre-existing kidney conditions. Regular monitoring is essential.
Angioedema: This is a rare but severe allergic reaction causing swelling of the face, lips, throat, and tongue, which can lead to breathing difficulties.

If any of these serious symptoms occur, medical help should be sought immediately. It is crucial to have regular check-ups with a healthcare provider to monitor for these potential issues, especially if there are other risk factors present.

The Role of Open Communication with Your Doctor

To ensure the safest and most effective treatment with losartan, it is vital to maintain open communication with your healthcare provider. Discuss any side effects, no matter how mild, as they can provide strategies to manage them or adjust your medication if necessary. For those with a history of ACE inhibitor-induced cough, losartan often offers a suitable alternative with a lower risk of this specific side effect. Adhering to the prescribed dosage, along with regular monitoring of blood pressure and kidney function, is key to a positive outcome.

It is also important to consider lifestyle factors in conjunction with losartan therapy. Maintaining a healthy, low-salt diet and staying hydrated can help regulate blood pressure and minimize symptoms like dizziness. Additionally, avoiding non-prescription medications, herbal supplements, and salt substitutes that can affect blood pressure is recommended unless approved by your doctor. For more detailed information on losartan, consult the MedlinePlus drug information page.

Conclusion

Dizziness is the most commonly encountered side effect of losartan, typically occurring as the body adjusts to the medication's blood pressure-lowering action. While usually mild and manageable, other common side effects like upper respiratory infections and back pain are also possible. Serious but rare side effects such as hyperkalemia and angioedema require careful monitoring. Open communication with your doctor, along with adherence to prescribed treatment and recommended lifestyle changes, is crucial for safely and effectively managing your condition while minimizing side effects. Losartan offers a valuable alternative for patients who experience intolerable side effects, particularly cough, with ACE inhibitors.

Frequently Asked Questions

Dizziness from losartan is typically temporary, especially when first starting the medication or adjusting the dose, and should improve over time as your body gets used to the new blood pressure level.

Yes, losartan is often a preferred alternative for patients who experienced a persistent, dry cough with ACE inhibitors, as it has a significantly lower incidence of this side effect.

To reduce dizziness, try getting up slowly from a sitting or lying position, stay well-hydrated, and avoid excessive alcohol consumption. Report persistent or severe dizziness to your doctor.

Signs of high potassium (hyperkalemia) can include muscle weakness, an irregular heartbeat, unusual tiredness, and chest pain. If you experience these symptoms, contact your doctor immediately.

Swelling of the face, lips, tongue, or throat (angioedema) is a rare but serious allergic reaction to losartan. It requires immediate medical attention.

Yes, losartan can cause changes in kidney function, especially in people with pre-existing kidney disease. Your doctor will monitor your kidney health with regular blood tests.

While taking losartan, you should be mindful of your potassium intake and avoid salt substitutes that contain potassium, as this medication can raise potassium levels in the blood.