What is Onkeito?

Onkeito is a Japanese Kampo herbal formula for menstrual problems. Its name means "warming the menses decoction". It is a fixed blend of about twelve herbs, taken as a drink or granule.

Kampo doctors give it for irregular periods, period pain and light, dragging bleeding. It is also used for cold hands and feet, dry lips and hot palms. In Japan it is a ministry-approved Kampo formula, sold as Tsumura 106.

The honest evidence picture is simple. The traditional record is long and clear, but good human trial data is thin. Long use in a tradition is not proof that a remedy works.

How does Onkeito work?

No one has shown how Onkeito works in the body. That is the plain answer.

Kampo theory says the blend warms the womb and moves "blood stasis", a traditional idea of stuck or cold blood. This is a way of choosing the formula for a patient. It is not a lab finding.

Some single herbs in the blend have been studied in cells and animals. In that work they appear to affect blood flow, hormone signals and smooth muscle. Whether any of this happens in women who take the finished formula is not established.

What forms does Onkeito come in?

Most people take Onkeito as a granule powder that dissolves in hot water. In Japan this is the ministry-approved product Tsumura 106.

It also comes as a classic decoction. The dried herbs are boiled in water and the liquid is drunk warm. Tablets and capsules exist but are less common.

Buy only from a licensed maker or a trained practitioner. Hange must be correctly processed, and home-made mixes can get that step wrong.

Where it comes from:

Onkeito comes from the Jin Gui Yao Lue, a Chinese medical text from around 200 CE. There it is called Wen Jing Tang.

Japanese Kampo doctors took it up and have used it for centuries. Japan's health ministry later approved it as a standard prescription Kampo formula, Tsumura 106.

It is still used in Chinese and Korean herbal practice under its older name. That gives it a classical standing across more than one tradition.

What does Onkeito help with?

• Irregular or missed periods: This is the classic Kampo use. Practitioners pick it for women with cool skin, cold feet and an unsteady cycle. Human trial evidence is thin. Small Japanese reports describe use for absent or irregular cycles. We could not identify a large, well-run trial to point you to.
• Period pain (cramps): Traditional use is well documented for cramping with a cold, dragging feeling. We found no good human trial testing Onkeito against a dummy treatment for period pain. Several other Kampo formulas are chosen more often for this.
• Light, prolonged or spotting-type bleeding: Kampo texts describe this pattern as a key sign for the formula. Bleeding that trickles on for days is the classic picture. There is no trial evidence we can cite. New or changed bleeding always needs a doctor's check first.
• Menopause symptoms: It is used for flushes in the face with cold feet and dry lips. This mixed hot-and-cold picture is the traditional target. Human evidence is limited and mostly small Japanese case reports. Treat any benefit as unproven.
• Cold hands and feet: The formula is named for warming, and this is a common reason it is chosen. No human trial has measured this for Onkeito. The claim rests on traditional use only.
• Trouble conceiving linked to irregular cycles: Kampo practice has long used it where cycles are irregular and the woman feels cold. This is traditional use, not proven fertility treatment. See a doctor about fertility rather than treating it yourself.

Which foods are rich in Onkeito?

1. Fresh and dried ginger (Shokyo): the kitchen spice is one of the herbs in the blend
2. Cinnamon bark (Keihi): the same bark used as a spice
3. Licorice sweets and licorice tea: these hold glycyrrhizin, the same compound as Kanzo

Practical Tips:

Onkeito is not a nutrient found in food. While taking it, cut back on licorice sweets and tea, since the glycyrrhizin adds up.

What are the side effects of Onkeito?

• Nausea, stomach ache or loss of appetite
• Diarrhoea or loose stools
• Rash, redness or itching
• Swelling of the face, hands or ankles
• Weight gain from held fluid
• Raised blood pressure
• Low potassium (hypokalaemia), with muscle weakness, cramps or a fluttering heartbeat
• Liver injury, shown by yellow skin or eyes, dark urine and deep tiredness
• Interstitial pneumonia (a rare lung reaction), with new dry cough, fever and breathlessness

Good to know:

Most people who take Onkeito have no trouble with it. Mild stomach upset and rash are the usual complaints.

The serious effects are uncommon but real. Licorice (Kanzo) in the blend can hold salt and water, push blood pressure up and drop potassium. Low potassium can affect heart rhythm.

Liver injury has been reported with Evodia at excess dose. Rare lung reactions are known across Kampo formulas. Stop the formula and get medical help if any of these appear.

How much Onkeito should you take?

• Recommended daily: In Japan the usual adult dose of the granule is 7.5 g a day. This is split into two or three doses. Decoction doses vary with the practitioner and the batch. There is no agreed dose outside licensed Kampo practice. Do not raise the dose on your own. Higher doses raise the risk of low potassium and liver problems.
• Best time of day: Usually two or three times a day, spread across the day. Many Kampo makers advise taking it before meals or between meals.
• With or without food: Take it on an empty stomach, before or between meals, with warm water. If it upsets your stomach, take it with food instead.
• Time to effect: Any change is slow. Most traditional use expects one to three cycles, not days.
• How long to take it: Give it two to three menstrual cycles, then review. If nothing has changed, stop and see a doctor. Long use needs watching because of the licorice in the blend. Ask your doctor to check your blood pressure and potassium if you take it for months.