Educational information, not medical advice — ask your doctor or midwife.
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Heiisan is a traditional Japanese Kampo stomach remedy, taken for a heavy, bloated, sluggish feeling after eating. Its Latin-style name translates as "level stomach", meaning it was meant to settle and calm the stomach. It is usually sold as a powdered or granulated extract you dissolve in hot water.
This entry is filed under a single Kampo (Japanese) heading, but Heiisan is not one herb. It is a fixed blend, and the herb that matters most for safety is kanzo (licorice root). Licorice is why this remedy has real drug interactions and a real list of people who must not take it.
What is it used for? Mild everyday digestive complaints: fullness after meals, bloating, poor appetite, loose stools and a coated tongue in the Kampo way of assessing patients.
Evidence verdict: Heiisan has deep classical standing across East Asian medicine, but we could not identify good published human trials of this formula, so its benefit is not proven. Long traditional use tells you a remedy has been trusted; it does not tell you it works, and that distinction applies to everything below.
The honest answer is that nobody has shown how Heiisan works in people. The explanations below are proposals, not proven mechanisms.
In Kampo theory, Heiisan is said to dry "dampness" in the stomach and get stalled digestion moving again. That is a traditional model of the body, not a description of measurable biology.
In laboratory terms, the bitter and aromatic herbs in the blend may stimulate digestive juices and ease spasm in the gut wall, and ginger may help with nausea. This work is mostly in test tubes and animals.
Licorice root is the one part with well-documented effects in humans, and they are mostly unwanted ones. Its main compound acts on the kidneys and can raise blood pressure and lower potassium.
Granulated extract sachets are the standard form in Japan. You stir the granules into hot water and drink them.
Other forms you may meet:
Loose powder, the classical preparation, mixed with hot water.
Tablets or capsules of dried extract.
Raw dried herb packs for decoction (simmering in water), usually dispensed by a practitioner.
Products vary a lot in how much licorice they contain. Check the label for kanzo or glycyrrhizin content before you take it alongside anything else.
Heiisan comes from the Chinese formula Pingwei San, recorded in the Song dynasty pharmacy manual Taiping Huimin Hejiju Fang around the year 1110.
It passed into Japanese Kampo practice and has stayed in routine use there for centuries. It is also used in Korean medicine. Today it is a licensed Kampo preparation covered by Japanese national health insurance.
Stop taking Heiisan and see a doctor promptly if you notice swelling in your ankles, face or hands, a bad headache, muscle weakness or cramps, or unusual tiredness. These can be signs of pseudoaldosteronism (a licorice reaction in which the body holds salt and water, blood pressure climbs and blood potassium falls).
Get urgent medical help if you have chest pain, a pounding or irregular heartbeat, fainting, severe muscle pain, or dark brown urine.
See a doctor rather than continuing this remedy if your indigestion has not improved after about two weeks, or at any point if you have unexplained weight loss, difficulty swallowing, vomiting blood, black or bloody stools, or a persistent stomach pain that wakes you at night.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
Reviewed by the HealisticMD editorial team How we grade evidence →
The published evidence for Heiisan is weak or absent. That usually means no controlled trial has tested it, not that a trial found it ineffective — the two are different, and we grade only what has been published.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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