What Medication Cannot Be Taken with Losartan?

October 10, 2025 •

3 min read

Approximately 38.6 million Americans filled a prescription for losartan in 2021, a common medication for high blood pressure and other heart conditions. For these patients, understanding what medication cannot be taken with losartan is crucial to prevent dangerous health complications, such as serious electrolyte imbalances or kidney problems.

Quick Summary

This guide details key drug classes and supplements that interact dangerously with losartan, posing risks like dangerously high potassium levels, kidney damage, and excessively low blood pressure.

Key Points

Avoid Potassium Additives: Do not take potassium supplements, potassium-sparing diuretics, or potassium-containing salt substitutes with losartan due to the risk of hyperkalemia.
Steer Clear of Dual RAAS Blockade: Combining losartan with other RAAS-blocking medications, such as ACE inhibitors (e.g., lisinopril) or aliskiren, can lead to severe hypotension and kidney problems.
Be Cautious with NSAIDs: Nonsteroidal anti-inflammatory drugs like ibuprofen can reduce losartan's effectiveness and increase the risk of kidney damage, especially in vulnerable patients.
Monitor Lithium Levels: Losartan can cause a dangerous increase in lithium levels, requiring careful monitoring if both drugs are prescribed concurrently.
Never Take During Pregnancy: Losartan is contraindicated in pregnancy and carries a black box warning due to the high risk of serious fetal injury or death.

Key Medications and Supplements to Avoid with Losartan

Losartan, an angiotensin II receptor blocker (ARB), works by relaxing blood vessels and lowering blood pressure. However, its mechanism of action can be dangerously affected by other drugs and supplements, leading to serious health risks. It is essential to discuss all medications with a healthcare provider before starting losartan or adding new drugs to your regimen.

Medications and Supplements that Increase Potassium

Losartan can increase the body's potassium levels, and combining it with other agents that also raise potassium can lead to hyperkalemia. This condition can cause symptoms from muscle weakness to irregular heartbeats and can be life-threatening.

Potassium-sparing diuretics like spironolactone, eplerenone, and triamterene can significantly elevate potassium when combined with losartan. Over-the-counter potassium supplements and salt substitutes using potassium should also be avoided, particularly in individuals with kidney issues. Immunosuppressants such as tacrolimus and certain antibiotics like sulfamethoxazole/trimethoprim may also cause hyperkalemia with losartan.

The Perils of Dual RAAS Blockade

The RAAS system regulates blood pressure. Combining losartan with other RAAS blockers can excessively lower blood pressure and impair kidney function.

ACE inhibitors (e.g., lisinopril, enalapril) and other ARBs (e.g., valsartan) are generally not recommended with losartan due to increased risk of hypotension, kidney problems, and hyperkalemia. The direct renin inhibitor aliskiren should also not be combined with losartan, especially in patients with diabetes or kidney disease.

Nonsteroidal Anti-inflammatory Drugs (NSAIDs)

NSAIDs, such as ibuprofen and naproxen, pose a risk when taken with losartan, particularly for vulnerable populations. NSAIDs can reduce losartan's effectiveness by raising blood pressure and increase the risk of kidney damage or acute kidney injury when combined with losartan.

Lithium

Losartan can interfere with how the body processes lithium, a medication used for bipolar disorder. This interaction can lead to a buildup of lithium and cause toxicity. If this combination is necessary, close monitoring of lithium levels is required.

Other important interactions and considerations

Pregnancy: Losartan is contraindicated during the second and third trimesters of pregnancy due to the risk of fetal injury or death.
Grapefruit: Grapefruit and its juice may affect losartan's metabolism, potentially reducing its effectiveness.
Alcohol: Excessive alcohol consumption can amplify losartan's blood pressure-lowering effect, increasing the risk of dizziness.
Herbal products: Some herbal supplements can interact with losartan, either by affecting potassium levels or influencing metabolism.

Summary of Key Losartan Interactions


Drug Class / Supplement	Examples	Potential Risk with Losartan
Potassium-sparing Diuretics	Spironolactone, Triamterene, Eplerenone	Hyperkalemia (high blood potassium)
Potassium Supplements	Potassium chloride, salt substitutes	Hyperkalemia
ACE Inhibitors	Lisinopril, Enalapril	Excessive hypotension, hyperkalemia, kidney damage
Other ARBs	Valsartan, Candesartan	Excessive hypotension, hyperkalemia, kidney damage
Aliskiren	Tekturna	Severe hypotension, hyperkalemia, kidney damage (especially with diabetes)
NSAIDs	Ibuprofen, Naproxen, Celecoxib	Reduced blood pressure control, kidney damage
Lithium	Lithium (Lithobid)	Increased lithium levels, leading to toxicity

Conclusion

Understanding what medication cannot be taken with losartan is vital for medication safety. Combining losartan with drugs affecting potassium, other RAAS inhibitors, or NSAIDs can cause serious side effects like electrolyte imbalances, kidney damage, and blood pressure fluctuations. Always inform your healthcare team about all medications and supplements you use. Seek immediate medical attention for unusual symptoms like severe dizziness or irregular heartbeats.

For more information, see the official {Link: MedlinePlus drug information https://medlineplus.gov/druginfo/meds/a695008.html}.

Frequently Asked Questions

It is not recommended to take NSAIDs like ibuprofen with losartan, particularly for chronic or frequent use. NSAIDs can reduce losartan's effectiveness and increase the risk of kidney damage, especially if you are elderly or dehydrated. Consult your doctor for a safer pain relief alternative.

Taking potassium supplements or using salt substitutes containing potassium while on losartan can lead to a dangerously high level of potassium in your blood, a condition called hyperkalemia. This can cause serious cardiac and muscle problems.

No, combining losartan (an ARB) with an ACE inhibitor like lisinopril is generally avoided. This 'dual blockade' of the RAAS pathway can cause severe hypotension, increased risk of hyperkalemia, and kidney dysfunction.

For most people, a diet including potassium-rich foods is fine, as studies have shown it does not typically cause an interaction with losartan. However, individuals with kidney problems or other risk factors should speak with their doctor about dietary restrictions.

Signs of a dangerous interaction can include severe dizziness, fainting, weakness, numbness or tingling, nausea, confusion, or irregular heartbeat. If you experience these symptoms, contact your healthcare provider immediately.

While there's no known direct interaction, excessive alcohol can further lower blood pressure, which may increase side effects like dizziness and lightheadedness when taking losartan. Always follow your doctor's recommendations regarding alcohol consumption.

Losartan can increase lithium levels in your body, increasing the risk of lithium toxicity. Close monitoring of lithium levels is required, and dosage adjustments may be necessary if the two medications are used together.

Losartan carries a black box warning because it can cause serious injury or death to an unborn baby, particularly in the second and third trimesters. It is strictly contraindicated in pregnant women.