If you choose to buy the plant in a herbalist, this is how you can make the tea: place two tablespoons of horsetail in one litre of water and leave to boil for ten minutes. Turn off heat and let sit for fifteen minutes. Then strain the water. Drink a litre of tea throughout the day, but do not consume more than this amount daily.

https://tophealthsystem.com/consume-horsetail-to-lose-weight/