What Supplements Should Be Avoided When Taking Losartan?

October 12, 2025 •

4 min read

Losartan (Cozaar) is a commonly prescribed medication for high blood pressure, with over 15 million prescriptions dispensed in the US in 2021. However, many patients are unaware of potential interactions with dietary and herbal supplements. Understanding what supplements should be avoided when taking losartan is critical for preventing dangerous side effects and ensuring the medication's effectiveness.

Quick Summary

Losartan can interact with certain supplements, most notably potassium, which can lead to dangerously high blood potassium levels (hyperkalemia). Other supplements like grapefruit, certain herbal diuretics, and some potassium-rich herbs should also be avoided due to the risk of affecting the drug's efficacy or causing side effects.

Key Points

Potassium is the top concern: Avoid potassium supplements and salt substitutes containing potassium to prevent dangerously high blood potassium levels (hyperkalemia) when taking losartan.
Check your multivitamin: Some multivitamins contain potassium. Always read the label and consult a healthcare provider or pharmacist to ensure it is safe for you.
Say no to grapefruit: Grapefruit and grapefruit juice can increase losartan absorption, potentially leading to increased effects and side effects. It is best to avoid them completely.
Exercise caution with herbal remedies: Certain herbs like dandelion and ginseng can interact with losartan. Herbs high in potassium or with diuretic properties should be avoided.
Consult your doctor first: Always inform your healthcare provider about all supplements, vitamins, and herbal products you are taking before starting or continuing losartan.
Be mindful of cannabis and CBD: Interactions with cannabis products are not fully understood, so use caution and discuss any use with your doctor.
Monitor for symptoms: Watch for signs of hyperkalemia, such as irregular heartbeat, weakness, or tingling, and seek immediate medical attention if they occur.

The Primary Interaction: Losartan and Potassium

Losartan is an angiotensin II receptor blocker (ARB) that works by relaxing blood vessels to lower blood pressure. A well-known side effect of losartan is its tendency to increase potassium levels in the blood, a condition known as hyperkalemia. For this reason, adding more potassium through supplements can push levels into a dangerous range, leading to serious health problems.

Potassium Supplements and Salt Substitutes

Anyone taking losartan should avoid over-the-counter potassium supplements unless specifically instructed and monitored by their healthcare provider. It is also crucial to check the labels of any salt substitutes or low-sodium seasonings, as many use potassium chloride in place of sodium chloride. This can cause an unintentional and significant increase in potassium intake. Symptoms of hyperkalemia can include weakness, an irregular heartbeat, confusion, tingling in the extremities, and feelings of heaviness in the legs. If these symptoms occur, immediate medical attention is required.

Potassium-Rich Herbal Supplements

Beyond standard supplements, several herbal remedies can also contain significant amounts of potassium or affect kidney function, which influences potassium balance. Patients should be cautious with these products as they can contribute to the risk of hyperkalemia. Some of these include:

Chicory: A natural source of potassium.
Ginseng: Certain types have been linked to blood pressure changes and potential potassium effects.
Lemongrass: Known to have potassium content.
Water Lotus: This and other water-based herbs can contain higher levels of minerals.
Mugwort: An herb that can affect electrolyte balance.

Avoiding Interactions with Herbal and Food-Based Supplements

Several other supplements, particularly herbal remedies, should be avoided or used with extreme caution when on losartan. The reasons vary, from affecting drug metabolism to altering blood pressure in unwanted ways.

The Grapefruit Connection

Grapefruit and its juice have a well-documented history of interacting with many medications, and losartan is no exception. Grapefruit products can inhibit an enzyme in the intestinal tract that is responsible for breaking down losartan. This can lead to increased absorption of the medication, potentially increasing its effects and side effects. The best course of action is to avoid grapefruit entirely when taking losartan to ensure consistent drug levels in the body.

Herbal Diuretics

Some herbal supplements have a diuretic effect, meaning they cause the body to excrete water. Combining these with losartan or a losartan-containing diuretic (like losartan-hydrochlorothiazide) can intensify the effects and potentially lead to dehydration or electrolyte imbalance. Examples of herbal diuretics to be wary of include dandelion, uva ursi, juniper, and horsetail.

Other Notable Interactions

While less directly related to hyperkalemia, other supplements may pose risks:

Ginger: This common supplement may increase the absorption of losartan, which could amplify its effects.
Cannabis and CBD: There is limited research on the interaction between cannabis products and losartan. However, given cannabis's potential effects on blood pressure and heart rate, it is crucial to consult a doctor before combining them.

Managing Multivitamins and Nutritional Intake

Many multivitamins contain potassium, and while the amounts are typically small compared to dedicated supplements, they can still contribute to overall intake. It is essential to read the label of any multivitamin or mineral supplement to check its potassium content. Consulting a pharmacist can help determine if a specific multivitamin is safe to use. For potassium-rich foods like bananas, avocados, and spinach, most individuals on losartan can continue to eat them in moderation, but those with kidney problems should discuss their dietary intake with a healthcare professional.

Comparison Table: Safe vs. Risky Supplements with Losartan


Supplement Category	Example(s)	Risk Level with Losartan	Reason for Risk	Recommendation
Potassium Supplements	Potassium chloride, gluconate	High	Increases blood potassium, causing hyperkalemia	Avoid unless medically advised and monitored
Salt Substitutes	Many 'low-sodium' products	High	Replaces sodium with potassium, increasing intake	Avoid and use other seasonings
Grapefruit Products	Grapefruit, grapefruit juice	Moderate to High	Interferes with losartan metabolism, altering effectiveness	Avoid completely
Herbal Diuretics	Dandelion, Uva ursi	Moderate	Adds to diuretic effect, risk of dehydration/imbalance	Avoid
Potassium-Rich Herbs	Ginseng, Chicory	Moderate	Adds to potassium load, increasing hyperkalemia risk	Consult doctor before use
Ginger	Ginger root, capsules	Moderate	May increase losartan absorption and effects	Use with caution and consult doctor
Cannabis / CBD	CBD oil, cannabis products	Moderate	Potential for blood pressure effects; limited data on interactions	Consult doctor before use
Multivitamins	Standard multivitamin with minerals	Low to Moderate	May contain potassium; potency varies	Check label; consult doctor or pharmacist
Most Standard Vitamins	Vitamin C, B-vitamins	Low	No known interaction with losartan	Generally safe, but inform doctor

Conclusion

While supplements are often perceived as harmless, their interaction with prescription medications like losartan can lead to significant health risks. The most critical interaction to be aware of is with potassium, which can lead to life-threatening hyperkalemia when combined with losartan. Patients must be proactive in reading labels for potassium content in supplements and salt substitutes. Other potential interactions, particularly with grapefruit and certain herbal remedies, also warrant caution and avoidance. The safest approach is always to discuss all dietary and herbal supplements with your healthcare provider before starting losartan. Maintaining open communication with your medical team is the best strategy for avoiding harmful interactions and ensuring the safe and effective management of your health condition. For more information on losartan interactions, consult a reliable source such as the Losartan entry on Drugs.com.

Frequently Asked Questions

There is no widely reported interaction between losartan and magnesium supplements. However, it is important to discuss all supplements with your doctor before starting them, as some combinations, particularly with diuretics, can affect electrolyte balance.

Hyperkalemia is a condition characterized by dangerously high levels of potassium in the blood. Losartan can cause blood potassium to rise, and adding potassium through supplements or salt substitutes significantly increases the risk of this condition, which can be life-threatening.

Yes, to avoid potassium-based salt substitutes, you can flavor your food with natural alternatives like garlic, lemon juice, paprika, onion powder, and other herbs and spices.

If you realize you have taken a supplement known to interact with losartan, contact your doctor or pharmacist immediately. Depending on the supplement and the amount, they may advise you on next steps or if a blood test is needed to check your potassium levels.

Yes, if you are taking a combination medication containing losartan, the same rules regarding potassium supplements and other interactions apply. You should always discuss your medication regimen with your doctor.

Carefully read the nutritional information on the multivitamin label and look for the potassium content. You should also take the multivitamin to your doctor or pharmacist so they can review the ingredients and advise you on its safety.

For most people, eating naturally potassium-rich foods in moderation while taking losartan is safe and does not cause interactions. However, those with kidney problems or other risk factors should consult their doctor for personalized dietary advice.