Is it safe to take horsetails every day? Potential Risks and Benefits

December 2, 2025 •

4 min read

While horsetail has been used as a traditional remedy for centuries, long-term or excessive daily consumption is not generally advised due to potential health concerns. This is primarily because of its diuretic properties and an enzyme called thiaminase, which can interfere with vitamin B1.

Quick Summary

Daily horsetail intake is generally discouraged for long-term use due to risks like thiamine deficiency and kidney issues, with safety dependent on duration, dosage, and specific health factors.

Key Points

Long-term Risk: Daily horsetail intake for extended periods is not recommended due to serious health risks like vitamin B1 deficiency and kidney issues.
Thiaminase Content: Horsetail contains thiaminase, an enzyme that can cause thiamine (vitamin B1) deficiency with prolonged or excessive use.
Diuretic Effects: Its potent diuretic properties can lead to kidney irritation and an electrolyte imbalance, including dangerously low potassium levels (hypokalemia).
Toxic Contamination: It is critical to ensure horsetail supplements use the correct species (Equisetum arvense), as toxic relatives like Equisetum palustre exist and contamination has occurred.
Contraindications: Horsetail should be avoided by pregnant or breastfeeding women, individuals with kidney problems, alcohol use disorder, diabetes, or those on certain medications.
Dosage and Duration: Use should be limited to short-term courses, typically 2-6 weeks, with breaks in between. Dosage depends on the form and should not exceed recommended limits.
Professional Guidance: Always consult a healthcare provider before taking horsetail to assess individual safety and determine appropriate use.

The Primary Concern: Thiaminase and Vitamin B1 Deficiency

One of the most significant risks associated with prolonged horsetail intake stems from an enzyme called thiaminase. This enzyme actively breaks down thiamine, or vitamin B1, in the body. While processing can neutralize this enzyme, consuming raw horsetail or certain unprocessed supplements can lead to a thiamine deficiency over time. Thiamine is crucial for energy metabolism and proper nerve function, and a deficiency can cause symptoms such as fatigue, neurological problems, and nerve damage. For this reason, many health authorities advise against long-term, continuous daily use of horsetail products that are not certified as thiaminase-free. This risk is particularly acute for individuals with pre-existing low thiamine levels, such as those with chronic alcohol use disorder.

Potential Risks of Daily Horsetail Consumption

Beyond the risk of vitamin B1 deficiency, daily horsetail use presents several other potential health concerns that users should be aware of. These issues typically arise from prolonged use or excessive dosage.

Kidney Irritation: Horsetail is a known diuretic, meaning it increases urine production. With long-term, high-dose consumption, this can irritate the kidneys. The plant also has a high silica content, and late-harvested horsetail can have silica levels that are particularly irritating to the kidneys.
Electrolyte Imbalance: The diuretic effect of horsetail can lead to an excessive loss of electrolytes, specifically potassium. Low potassium levels, or hypokalemia, can cause symptoms like muscle cramps, weakness, and, in severe cases, dangerous heart rhythm problems. Users, especially those on other diuretics, must be cautious.
Toxic Species and Contamination: It is crucial to use the correct species, Equisetum arvense (field horsetail), for supplements. Other related species, such as Equisetum palustre (marsh horsetail), contain toxic alkaloids and are poisonous to humans and livestock. Contamination with toxic species has been reported in horsetail products. Furthermore, horsetail can concentrate heavy metals from its environment, another reason for concern regarding its source.
Nicotine Content: Horsetail naturally contains small amounts of nicotine. This means individuals with a nicotine allergy should avoid it.

Critical Considerations and Comparative Safety

Before embarking on a daily horsetail regimen, understanding the contrast between short-term and long-term use is crucial for safety and efficacy. This is especially important as many herbal supplements lack strict regulatory oversight.


Feature	Short-Term Use (e.g., 2-6 weeks)	Long-Term Use (Continuous Daily)
Thiamine Risk	Low risk for otherwise healthy individuals.	Increased risk of thiamine (vitamin B1) deficiency due to thiaminase.
Kidney Health	Generally well-tolerated at recommended doses.	Risk of kidney irritation due to persistent diuretic action and high silica levels.
Electrolyte Balance	Minor risk of imbalance, especially with adequate hydration.	Higher risk of potassium depletion, leading to hypokalemia.
Interactions	Potential for moderate interaction with certain medications.	Higher probability of clinically significant drug interactions.
Scientific Evidence	Some studies support short-term diuretic effects.	Insufficient long-term human data to confirm safety or effectiveness.

Who Should Avoid Horsetail?

Certain groups of people should not take horsetail under any circumstances or should only do so under strict medical supervision due to heightened risks.

Pregnant and Breastfeeding Women: Safety data is lacking for this population, and the potential for nicotine and thiaminase effects is a concern.
People with Kidney Disease: The diuretic effect and potential for potassium loss can worsen existing kidney conditions.
Diabetics: Horsetail may lower blood sugar levels, which could interact negatively with diabetes medication and cause dangerous hypoglycemia.
Individuals on Diuretic or Lithium Medications: Combining horsetail with other diuretics can cause potassium levels to drop too low. It can also interfere with the body's ability to eliminate lithium, leading to dangerous accumulation.
People with Alcohol Use Disorder: These individuals are often already thiamine deficient, and horsetail could worsen the condition.

Safe Usage Guidelines and Dosage

For those considering a short-term course of horsetail, consulting a healthcare provider is the most important step. A medical professional can help assess individual health factors and potential risks, as there is no universally recommended safe dosage. However, typical short-term recommendations based on existing studies and herbal traditions include:

Capsules: 300-600 mg per day, divided into 2-3 doses, for a period of 2-6 weeks. A clinical study saw a diuretic effect at 900 mg daily for 4 days.
Tea: 2-3 cups per day of an infusion made from the dried herb.
Cycling: To avoid long-term issues, some herbalists recommend cycling use, such as one month on and one to two weeks off.

Crucially, always purchase horsetail products from reputable manufacturers who can certify the correct species (Equisetum arvense) and confirm that processing has neutralized the thiaminase enzyme. This mitigates the risk of contamination and enzyme-related deficiencies.

Conclusion: Proceed with Caution and Professional Guidance

Is it safe to take horsetails every day? The consensus among health experts is that long-term daily use is not advised due to significant risks, including thiamine deficiency, kidney irritation, and electrolyte imbalances. While some healthy individuals may tolerate short-term use for specific conditions under a doctor's supervision, the lack of extensive human clinical research, the risk of toxic contamination, and various contraindications demand extreme caution. Always speak with a healthcare provider before beginning a horsetail regimen to ensure its appropriateness for your individual health needs and to confirm safe sourcing.

Visit WebMD for more comprehensive information on horsetail uses and safety concerns.

Frequently Asked Questions

No, it is not safe to take horsetail daily long-term. While it contains silica, which is often marketed for hair and nail health, the risk of thiamine deficiency and other side effects from prolonged use outweighs the unproven benefits.

Common side effects from short-term use include mild gastrointestinal discomfort and increased urination due to its diuretic properties. Long-term or excessive use can lead to more serious problems like thiamine deficiency and electrolyte imbalance.

The best way to avoid thiamine deficiency is to limit horsetail use to short periods (2-6 weeks) and not use it daily long-term. Some products are processed to remove the thiaminase enzyme, but consult a healthcare provider for the safest approach, which may involve thiamine supplementation.

Yes. Horsetail is a diuretic and contains silica. Excessive or long-term intake can irritate the kidneys, particularly if you have pre-existing kidney issues or consume late-season harvests with high silica concentrations.

You should avoid horsetail if you are pregnant, breastfeeding, have kidney disease, or suffer from alcoholism or thiamine deficiency. It should also be avoided by people taking diuretics, lithium, or medications for diabetes.

Always purchase horsetail from reputable manufacturers who can provide documentation that their product is derived solely from Equisetum arvense. Contamination with toxic species like Equisetum palustre is a known risk with unregulated sources.

Many experts and sources recommend limiting horsetail use to short-term courses, typically lasting between 2 and 6 weeks. Taking regular breaks between courses helps reduce the risk of long-term side effects.