Zeng Ye Tang
Quick Facts
- What it is: A classical three-herb Chinese formula, given as a single product, used traditionally for dryness — dry hard stools, dry mouth and thirst.
- Main uses: Constipation with dry, hard stools, Dry mouth and throat, Thirst after a fever
- Best for: Short-term dry constipation in an otherwise healthy adult, Dryness left after a feverish illness
- Active ingredients: Catalpol and other iridoid glycosides (from Rehmannia), Ophiopogonins (steroidal saponins from Ophiopogon), Harpagoside and harpagide (from Scrophularia), Plant sugars and mucilage (water-holding carbohydrate)
- Forms: Raw herbs for decoction (simmered tea), Concentrated granules, Teapills or tablets, Practitioner liquid extract
- Time to effect: One to two days for dryness and thirst; three to seven days for constipation.
- Side effects: Usually mild and digestive — loose stools, bloating, poor appetite. Rare allergic rash.
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What is Zeng Ye Tang?
Zeng Ye Tang is a Chinese herb formula made from three herbs. It is sold as one product, not as three separate herbs. People take it for dry, hard stools and for a dry mouth and throat.
Its English name is Increase the Fluids Decoction. It suits people who look dry, rather than "hot" or blocked up.
The three herbs are raw Rehmannia (Sheng Di Huang), Ophiopogon root (Mai Men Dong) and Scrophularia root (Xuan Shen). In Chinese medicine, these herbs are said to "moisten" the body. They are said to bring back body fluids.
Here is the evidence in one line. Its standing in tradition is strong and goes back a long way. But human trial evidence is thin, and we found no well-reported trial we trust.
Long use in a tradition is not proof that something works. That point applies to everything on this page.
How does Zeng Ye Tang work?
No one has shown clearly how this formula works in the body. So treat any account of how it works as a theory, not a fact.
In traditional terms, it is said to "increase the fluids to float the boat". The idea is that a dry gut cannot move stool along. So you add moisture, rather than force the bowel with a purgative (a strong laxative).
In lab terms, the likely story is much plainer. Rehmannia and Ophiopogon hold a lot of sugars and mucilage. Mucilage is a slimy plant carbohydrate that holds water.
That water can stay in the gut and soften stool. Lab and animal studies also report effects on saliva (spit) and on inflammation (swelling). But animal results often do not carry over to people.
This is not a stimulant laxative. It is not thought to work by irritating the bowel wall. It should not cause cramps the way senna or bisacodyl can.
What forms does Zeng Ye Tang come in?
You will usually meet it in one of these forms:
Raw herbs for a decoction. You simmer the three dried roots in water at home and drink the liquid as a tea. This is the classical form.
Concentrated granules. This is a powder or granule made from a water extract, which you stir into hot water. It is the most common modern form.
Pills or tablets, often called "teapills". They are handy, but each dose is usually weaker.
Liquid extracts made by a practitioner. These are sometimes adjusted with extra herbs to suit one person.
Where it comes from:
The formula comes from a book called Wen Bing Tiao Bian. The English title is Systematic Differentiation of Warm Diseases. Wu Ju-tong wrote it in 1798.
It was made for the dryness left behind after a feverish illness. In that state the tongue is dry and red, and the stool will not pass.
It became a standard teaching formula. Chinese medicine schools still teach it today.
It is a staple of one tradition: Chinese herbal medicine. Many cultures did not take it up on their own.
Who should avoid Zeng Ye Tang?
- Never take this together with Veratrum root (Li Lu): this combination is avoided completely in Chinese herbal medicine, and Veratrum can disturb heart rhythm.
- Do not use if you take digoxin or another drug for heart rhythm, unless your doctor has checked and agreed.
- Do not use if you take warfarin, apixaban, clopidogrel or another blood thinner, unless your doctor has checked and agreed.
- Do not use if you are pregnant or breastfeeding, as there is no safety information for these situations.
- Do not use if you already have diarrhoea, long-running loose stools, or a weak appetite with bloating — this formula is likely to make that worse.
- Do not use if your constipation comes with severe belly pain, vomiting, a swollen belly or no wind passing; this can mean a blocked bowel and needs urgent medical care instead.
- Do not use if you have diabetes and cannot check your blood sugar regularly, because the herbs may lower it further.
- Do not give it to a child without advice from a qualified practitioner.
- Do not use if you have had an allergic reaction to Rehmannia, Ophiopogon or Scrophularia before.
- Do not use it in place of treatment your doctor has prescribed for Sjogren's syndrome, cancer care or any other diagnosed condition.
When should you see a doctor?
Stop taking it and see a doctor if your constipation has not improved after two weeks, or if it keeps coming back.
Get medical advice promptly if you notice blood in your stool, unexplained weight loss, black or tarry stools, or a lasting change in your usual bowel pattern.
Get urgent care the same day for severe belly pain with vomiting and no wind or stool passing, or if you bruise or bleed easily while taking this alongside a blood thinner.
Call emergency services for swelling of the face, lips or tongue, a spreading rash, or trouble breathing.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
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