What Supplements Should Be Avoided with Losartan?

October 9, 2025 •

4 min read

According to a 2022 survey, nearly half of all US adults take nutritional supplements, but many are unaware of potential interactions. For those taking prescription medication like losartan, it is crucial to understand what supplements should be avoided with losartan to prevent dangerous side effects and ensure your treatment remains effective.

Quick Summary

Losartan can interact with certain supplements and foods, most notably those high in potassium and specific herbs, which can lead to complications like hyperkalemia or reduced medication effectiveness. Discussing all supplements and dietary choices with a healthcare provider is essential for safe medication management.

Key Points

Potassium Supplements are a Major Risk: Losartan can cause high blood potassium (hyperkalemia), and taking potassium supplements or using potassium-based salt substitutes can exacerbate this dangerous condition.
Grapefruit Interferes with Losartan Metabolism: Grapefruit and grapefruit juice can alter how losartan is metabolized, potentially decreasing its effectiveness.
Certain Herbs Can Cause Complications: Licorice root can increase blood pressure, while St. John's Wort can decrease losartan's efficacy, leading to negative health outcomes.
Always Consult a Healthcare Provider: It is vital to discuss any and all supplements, including seemingly harmless ones like multivitamins, with your doctor or pharmacist to avoid harmful interactions.
Look for High-Potassium Herbal Products: Be mindful that some herbal supplements, like Noni juice, can be high in potassium and should be avoided to prevent hyperkalemia.
Monitor for Symptoms of Interaction: Watch for signs of an interaction, such as muscle weakness, irregular heartbeat, or dizziness, and contact your doctor if they occur.
The FDA Does Not Regulate Supplements Strictly: Be aware that supplements lack the same strict regulatory oversight as prescription drugs, so contents and potency can vary.

Losartan, also known by the brand name Cozaar, is a commonly prescribed medication used to treat high blood pressure, lower the risk of stroke, and manage kidney problems related to diabetes. As an angiotensin II receptor blocker (ARB), losartan works by relaxing blood vessels to help blood flow more easily. While generally safe, the medication has a number of clinically significant interactions with certain supplements, herbal remedies, and foods that can lead to serious health complications.

The Danger of Excess Potassium (Hyperkalemia)

One of the most critical interactions to be aware of when taking losartan is with potassium. Losartan can increase the amount of potassium in your body, a condition known as hyperkalemia. This is especially true when it is combined with other substances that also raise potassium levels. Excessively high potassium can be life-threatening and may cause irregular heartbeats, nausea, or muscle weakness.

High-Potassium Supplements and Products to Avoid:

Potassium Supplements: Both prescription and over-the-counter potassium supplements, such as potassium chloride and potassium gluconate, should be avoided unless specifically directed by your doctor.
Potassium-Containing Salt Substitutes: Many sodium-free or low-sodium salt substitutes replace sodium with potassium. Using these products with losartan can significantly increase your potassium intake and risk of hyperkalemia.
High-Potassium Herbal Supplements: Certain herbal remedies contain naturally high levels of potassium, such as Noni juice. Always check the ingredients of any herbal product. Individuals with pre-existing kidney conditions or heart failure are at a higher risk and should be extra cautious.

Herbal Supplements to Avoid or Use with Caution

Many people incorrectly assume that because herbal supplements are 'natural,' they are safe to use alongside prescription medications. However, this is a dangerous misconception. The following herbal products have known or suspected interactions with losartan:

Licorice Root: Licorice contains a compound called glycyrrhizic acid, which is known to increase blood pressure and cause the body to retain salt and water. This directly counteracts the blood pressure-lowering effects of losartan. Even small amounts can pose a risk, especially for those with high blood pressure, heart disease, or kidney disease.

St. John's Wort: This popular herbal supplement for depression has been shown to weaken the effects of many medications, including blood pressure drugs like losartan. It works by inducing liver enzymes that break down the drug, potentially making losartan less effective at controlling blood pressure.

Ginseng (Panax ginseng): There is conflicting information about ginseng's interaction with blood pressure medication. Some studies suggest it might affect losartan metabolism, though others report no significant interaction. Given the uncertainty and its potential to affect blood pressure, it is best to consult a doctor before combining ginseng with losartan.

Herbal Diuretics: Herbs with diuretic properties, such as dandelion, uva ursi, and juniper, should be avoided. These can increase the diuretic effect when taken with combination drugs containing losartan and a diuretic (e.g., losartan-HCTZ), potentially causing fluid and electrolyte imbalances.

Other Notable Interactions

Grapefruit and Grapefruit Juice: This is a well-documented interaction for many medications. While some research is conflicting, grapefruit can inhibit the enzyme (CYP2C9) that helps metabolize losartan's active form. This could potentially alter the drug's effectiveness, making it either less effective or increasing adverse effects. It is generally advised to avoid grapefruit and its juice while on losartan therapy.

Vitamin E: While newer studies have shown no significant interaction, older studies suggested that high doses of Vitamin E could affect blood pressure in people with type 2 diabetes. Due to the conflicting data, discussing high-dose Vitamin E supplementation with a healthcare provider is recommended.

The Losartan and Supplement Interaction Comparison


Supplement/Substance	Type of Interaction	Risk Level	Effect on Losartan/Body
Potassium Supplements	Additive Effect	High	Can cause hyperkalemia (dangerously high potassium levels).
Potassium Salt Substitutes	Additive Effect	High	Can significantly increase potassium intake and risk of hyperkalemia.
Grapefruit/Grapefruit Juice	Metabolic Interference	Moderate	Can alter the metabolism of losartan, decreasing its effectiveness.
Licorice Root	Additive Effect	High	Can raise blood pressure and cause fluid retention, working against losartan.
St. John's Wort	Metabolic Interference	Moderate to High	Reduces the effectiveness of losartan by speeding up its breakdown.
Ginseng	Uncertain/Metabolic	Low to Moderate	Conflicting evidence on interaction, but warrants caution.
Herbal Diuretics	Additive Effect	Moderate	Can cause excess fluid and potassium loss, especially with combined therapies.

General Precautions for Supplement Use

Given the varied nature of interactions, a cautious approach is best. Supplements are not regulated by the FDA with the same stringency as prescription medications, meaning the potency and purity can vary significantly between products.

Inform Your Doctor: Before starting any new supplement, always inform your doctor or pharmacist. This includes seemingly harmless multivitamins, as they may contain ingredients like potassium that could interact.
Read Labels Carefully: Check the ingredient list of all over-the-counter products, including supplements, herbal teas, and protein powders, for potentially interacting substances.
Be Aware of Symptoms: Pay attention to any new symptoms that arise after starting a new supplement. Symptoms like weakness, irregular heartbeat, or dizziness could be signs of an interaction.
Choose Reputable Brands: Opt for supplements that have been independently tested by third-party organizations like USP or NSF to ensure the ingredients and dosages are accurately listed.

Conclusion

Understanding what supplements should be avoided with losartan is crucial for anyone managing their blood pressure with this medication. The risk of dangerous interactions, particularly with potassium and certain herbs, highlights the importance of open communication with healthcare providers. Never assume a supplement is safe just because it is natural or sold over-the-counter. By carefully managing your diet and supplement intake, you can help ensure your losartan therapy is both safe and effective. For further reading on medication interactions, a reputable resource like the National Institutes of Health provides valuable information on integrative health topics (https://www.nccih.nih.gov/health/using-dietary-supplements-wisely).

Frequently Asked Questions

No, you should not take potassium supplements with losartan unless specifically instructed by your doctor. Losartan can increase your body's potassium levels, and adding a supplement can cause a dangerous condition called hyperkalemia.

Yes, grapefruit and grapefruit juice can interfere with the metabolism of losartan, potentially making it less effective. It is best to avoid consuming grapefruit products while taking this medication.

No, many salt substitutes replace sodium with potassium. This can cause dangerously high potassium levels when combined with losartan, so it's important to read labels carefully and avoid these products.

No, you should avoid taking St. John's Wort with losartan. This herb can reduce the effectiveness of losartan, potentially compromising its ability to manage your blood pressure.

Licorice root contains a substance that can raise blood pressure and cause salt and water retention, which works directly against the effects of losartan. This can make your blood pressure medication less effective.

While the amount of potassium in multivitamins is usually small, it is still important to consult your doctor or pharmacist before taking one. They can advise you on whether the level of potassium is safe for your specific health situation.

Symptoms of a severe interaction, such as hyperkalemia, can include irregular heartbeat, muscle weakness, confusion, or tingling in the hands and feet. If you experience any of these, seek immediate medical attention.

It is safest to assume that any herbal supplement could have an interaction, as many are not well-studied in combination with prescription drugs. Always speak with your healthcare provider before taking any herbal remedies.