Research
Horsetail for Bladder Health: Evidence, Interactions and Cautions
Horsetail is an ingredient used in bladder supplements marketed to women. Below is what it has actually been studied for, how strong that evidence is, the drug interactions and cautions on record, and the primary source our grade rests on — all drawn from the HerWellReport ingredient dataset.
Also sold as: Equisetum arvense; field horsetail; shavegrass; Equiseti herba
What the evidence says about Horsetail
The EMA's herbal committee registered horsetail on traditional use only, which means long-standing use rather than demonstrated efficacy. The strongest human study in its assessment report is a double-blind randomised trial in 36 healthy men, where 900 mg a day of dried extract for four days produced a negative fluid balance of about -322 ml, comparable to hydrochlorothiazide, but with no significant change in sodium or potassium excretion. That is a mild diuretic signal in healthy volunteers, not evidence that it treats any bladder symptom.
The grade "traditional" means: traditional — A long history of use but little or no human trial evidence for this outcome. Grades are explained in full on our methodology page.
Read the primary source this grade rests on (opens in a new tab).
Horsetail drug interactions
No documented drug interactions in the sources we checked. That is not the same as proof of safety alongside your medication — it usually means the question has not been studied. Ask a pharmacist before combining it with prescription drugs.
Who should be careful with Horsetail
- Not if you have been told to restrict fluids, for example in severe heart or kidney disease
- Not in pregnancy or breastfeeding
- Not under 12 years
- Use for 2 to 4 weeks only
- Buy from a reputable source, as the toxic species Equisetum palustre is a known adulterant
Read more on HerWellReport
- Best Bladder Control Supplements for Women (2026): What’s Actually in Them
- Confitrol24 Review (2026): The Trial Is Real, But the Label Doesn’t Say How Much
- Urox Bladder Control Review (2026): The Trial Behind It, and the Hidden Dose
This entry is generated from row "Horsetail" of the HerWellReport ingredient dataset (v2.1, updated 2026-09-23). The dataset is free to reuse under CC BY 4.0 — how to cite it. Ingredient evidence is not evidence for any finished product, and nothing here is medical advice.