What should you avoid while taking losartan? A guide to safe medication use

October 10, 2025 •

5 min read

Losartan is one of the most commonly prescribed blood pressure medications in the U.S., belonging to the class of drugs known as angiotensin II receptor blockers (ARBs). When taking losartan, it is crucial to understand what should you avoid while taking losartan to ensure its effectiveness and prevent dangerous side effects, particularly regarding certain medications, supplements, and dietary choices.

Quick Summary

Losartan requires caution with potassium supplements, certain salt substitutes, and specific medications like NSAIDs, ACE inhibitors, and diuretics. These interactions can lead to high potassium levels, kidney damage, or excessively low blood pressure.

Key Points

Avoid Potassium Supplements: Losartan can increase blood potassium levels, so taking extra supplements or using potassium-based salt substitutes can cause dangerous hyperkalemia.
Limit NSAIDs: Over-the-counter pain relievers like ibuprofen can reduce losartan's effectiveness and increase the risk of kidney damage, especially with prolonged use.
Do Not Double-Block the RAS System: Combining losartan with ACE inhibitors (like lisinopril) or aliskiren is unsafe and significantly increases the risk of hypotension, hyperkalemia, and kidney issues.
Stay Clear of Grapefruit: Grapefruit and its juice can interfere with losartan's metabolism, potentially making the medication less effective.
Moderate Alcohol Intake: Both alcohol and losartan lower blood pressure, and combining them can cause excessive drops in blood pressure, leading to dizziness and fainting.
Watch for Dehydration: Vomiting, diarrhea, or heavy sweating can lead to low blood pressure and dehydration, which compounds the risk of kidney problems while on losartan.
Inform Your Doctor of All Medications: It is crucial to tell your healthcare provider about all drugs, vitamins, and herbal products you take to prevent harmful interactions.

Understanding Losartan and Its Actions

Losartan, often sold under the brand name Cozaar, works by blocking a hormone called angiotensin II. Angiotensin II normally causes blood vessels to narrow, which raises blood pressure. By blocking this effect, losartan helps relax and widen blood vessels, allowing blood to flow more freely and reducing blood pressure. This mechanism, while effective for treating high blood pressure and other conditions like diabetic nephropathy, can also impact other systems in the body, leading to potential interactions with other substances. A key side effect to monitor is an increase in blood potassium levels, known as hyperkalemia, which forms the basis for many dietary and medication restrictions.

Medications to Avoid or Use with Caution

Combining losartan with certain other medications can be dangerous, amplifying side effects, reducing effectiveness, or causing organ damage. Always inform your doctor or pharmacist of all medications you take, including over-the-counter (OTC) drugs and supplements.

Nonsteroidal Anti-inflammatory Drugs (NSAIDs)

This class of pain relievers, which includes common OTC and prescription drugs, is a major concern when taken with losartan.

How they interact: NSAIDs, such as ibuprofen (Advil, Motrin) and naproxen (Aleve), can increase blood pressure, counteracting the effects of losartan. Additionally, both losartan and NSAIDs can affect kidney function. When taken together, especially in older adults or those with pre-existing kidney disease, the risk of kidney damage increases significantly.
Safe alternatives: Your doctor may recommend safer pain relief options, such as acetaminophen, or closely monitor your kidney function if short-term NSAID use is unavoidable.

Angiotensin-Converting Enzyme (ACE) Inhibitors

Combining losartan with ACE inhibitors, another common class of blood pressure medication, is generally not recommended.

Why dual therapy is risky: Both losartan and ACE inhibitors (like lisinopril or enalapril) work on the same physiological system (the renin-angiotensin-aldosterone system) to lower blood pressure. Taking them together offers little to no additional benefit while dramatically increasing the risk of serious side effects, including severe low blood pressure (hypotension), high potassium levels (hyperkalemia), and acute kidney injury.

Diuretics (Water Pills)

Diuretics help the body eliminate excess fluid. The interaction with losartan depends on the type of diuretic.

Potassium-sparing diuretics: These diuretics, such as spironolactone and triamterene, already cause the body to retain potassium. Combining them with losartan, which also increases potassium levels, can lead to dangerously high potassium levels (hyperkalemia).
Loop and thiazide diuretics: These are less likely to cause hyperkalemia but still require monitoring. All diuretics combined with losartan require close monitoring of blood pressure, electrolytes, and kidney function.

Lithium

Lithium is a mood stabilizer used to treat bipolar disorder.

How they interact: Losartan can increase the level of lithium in the blood by affecting kidney function, potentially leading to lithium toxicity. Patients on both medications must have their lithium levels regularly monitored.

Dietary and Supplement Restrictions

What you eat and supplement with can also profoundly impact losartan's effectiveness and safety.

Potassium Supplements and Salt Substitutes

Losartan can cause an increase in your body's potassium levels. Taking extra potassium, whether through supplements or potassium-based salt substitutes, can push these levels into a dangerous range (hyperkalemia).

Recommendation: Never take potassium supplements or use potassium-containing salt substitutes without a doctor's explicit approval.

High-Potassium Foods

While most people can consume potassium-rich foods in moderation, those with pre-existing kidney conditions or other risk factors should be mindful. While a 2016 study suggests a high-potassium diet might not significantly impact levels in some individuals on losartan, those with kidney problems should still discuss dietary restrictions with their doctor. Examples of high-potassium foods include:

Bananas and Avocados
Spinach and Potatoes
Tomato paste and Juice
Beans and Legumes

Grapefruit and Grapefruit Juice

Some research suggests that grapefruit juice can interfere with the liver's metabolism of losartan, potentially reducing its effectiveness.

Mechanism: Grapefruit contains compounds that inhibit a liver enzyme (CYP2C9) responsible for converting losartan to its active form. This can lead to decreased concentrations of the active metabolite in your blood, making the medication less effective at controlling blood pressure.
Recommendation: It is generally best to avoid grapefruit and grapefruit juice entirely while on losartan, especially if a weakened blood pressure-lowering effect is suspected.

Alcohol

Alcohol consumption, particularly excessive intake, can lead to side effects when combined with losartan.

Mechanism: Both losartan and alcohol can lower blood pressure. Taking them together can cause an additive effect, leading to excessively low blood pressure (hypotension).
Symptoms: This can result in dizziness, lightheadedness, fainting, and headaches. The risk of these side effects is particularly high when first starting losartan, after a dose increase, or when treatment is restarted after an interruption.
Recommendation: Limit or avoid alcohol entirely while taking losartan, and consult your doctor to determine a safe level of consumption based on your individual health profile.

Comparison of Key Losartan Interactions


Interaction	Associated Substance	Potential Risk	Mechanism	Management	Monitoring
NSAIDs	Ibuprofen, Naproxen	Reduced efficacy, Kidney damage	Can increase blood pressure; both can impair kidney function.	Avoid NSAIDs; use alternatives like acetaminophen.	Blood pressure, kidney function.
Potassium Supplements	Salt substitutes, OTC supplements	Hyperkalemia (high potassium)	Losartan retains potassium; supplements add more.	Avoid supplements and potassium-based salt substitutes.	Serum potassium levels.
ACE Inhibitors	Lisinopril, Enalapril	Hyperkalemia, Hypotension, Kidney injury	Dual blockade of RAS system increases adverse effects.	Avoid combination unless under strict medical supervision.	Blood pressure, electrolytes, kidney function.
Grapefruit Juice	Grapefruit fruit or juice	Reduced efficacy	Inhibits CYP2C9 enzyme, reducing conversion to active metabolite.	Avoid grapefruit and juice completely.	Blood pressure.
Alcohol	Alcoholic beverages	Excessive hypotension	Additive blood pressure-lowering effect.	Limit or avoid; use caution when driving or operating machinery.	Dizziness, blood pressure.

Important Considerations and When to Contact Your Doctor

Certain conditions can increase your risk of losartan interactions. For example, if you are pregnant, have liver or kidney problems, or have diabetes, you may be at higher risk for complications. Dehydration, whether from illness, strenuous exercise, or hot weather, can also affect your kidney function and blood pressure while on losartan.

Immediately contact your healthcare provider if you experience any of the following:

Symptoms of hyperkalemia: Weakness, irregular heartbeat, confusion, numbness, or tingling.
Signs of kidney problems: Decreased urination, swelling in ankles or feet, confusion, or nausea.
Excessive low blood pressure: Dizziness, fainting, or lightheadedness.

Conclusion

While losartan is an effective medication for managing high blood pressure and other cardiovascular issues, its safety depends heavily on avoiding key interactions with other medications, foods, and substances. The most significant risks involve combining it with potassium supplements or other drugs that impact potassium levels, as well as pairing it with NSAIDs, which can damage the kidneys and reduce losartan's effectiveness. Dietary choices like grapefruit and alcohol consumption can also influence treatment outcomes and side effects. Always maintain open communication with your healthcare team about all the medications, supplements, and lifestyle factors in your life. This diligent approach is essential for safely and effectively managing your health while taking losartan. For more information on losartan and other drug interactions, consult reliable sources like the FDA drug labels and the NIH's StatPearls articles.

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider for any questions regarding a medical condition or treatment.

Frequently Asked Questions

You should generally avoid taking NSAIDs like ibuprofen (Advil, Motrin) or naproxen (Aleve) with losartan. The combination can reduce losartan's effectiveness in lowering blood pressure and significantly increases the risk of kidney damage, especially with regular use.

Losartan can increase blood potassium levels. While consuming potassium-rich foods in moderation is usually fine for healthy kidneys, you should talk to your doctor about limiting certain high-potassium foods like bananas, avocados, spinach, and potatoes, especially if you have kidney problems.

It is generally best to limit or avoid alcohol while taking losartan. Both can lower blood pressure, and combining them can lead to an excessive drop, causing dizziness, lightheadedness, and fainting, especially when starting the medication.

Grapefruit and grapefruit juice can inhibit an enzyme (CYP2C9) that metabolizes losartan. This can decrease the level of losartan's active metabolite in the body, potentially reducing its effectiveness in lowering blood pressure.

No, it is not recommended to take losartan (an ARB) with an ACE inhibitor (e.g., lisinopril or enalapril) simultaneously. This 'dual therapy' offers no proven extra benefit and significantly increases the risk of severe side effects, including high potassium and kidney damage.

Many salt substitutes replace sodium with potassium chloride. Since losartan increases potassium levels in the blood, using potassium-based salt substitutes should be avoided unless explicitly directed by a healthcare provider.

Symptoms of hyperkalemia can include muscle weakness, irregular heartbeat, numbness or tingling in the hands and feet, or feelings of heaviness in the legs. If you experience these symptoms, contact your doctor immediately.