Horsetail: how much to take
Horsetail is sold as a silica source for hair, nails and bones and as a mild diuretic. There are no good trials of oral horsetail for these uses.
Calculator Official intake Study doses Best form Safety Sources
Official daily intake
This is not an essential nutrient, so there is no official daily intake. Only study doses are shown.
Doses used in studies
These are doses tested in research, not personal advice. Some exceed the upper limit because they were short courses or given under medical care.
No study doses listed yet.
Best form and why
Food sources
Not a normal food.
Interactions
Ask your doctor if you take water tablets (diuretics).
Safety
Horsetail contains an enzyme that destroys vitamin B1 (thiamine). How much this matters for supplements in people is unclear, but long-term use is not well studied. Avoid in pregnancy.
Pregnant, breastfeeding, on medication, or managing a health condition? Check with a doctor or pharmacist before starting a supplement.
Sources
- Study Nakabayashi T (1957). Isolation of the thiamine-decomposing factor of horsetail. J Vitaminol (Kyoto) 3:129-134
Values checked: November 12, 2026.