What is Renjuin?

Renjuin is a herbal formula from Kampo, the traditional medicine of Japan. Its name means "string-of-pearls drink". It is given for dizziness, lightheadedness and a fluttering heartbeat.

Renjuin joins two older formulas. One is ryokeijutsukanto, long used for dizziness and palpitations. The other is shimotsuto, long used for pallor, tiredness and period problems.

It is a ministry-approved Kampo formula in Japan. In practice a Kampo doctor chooses it for a person, not for a disease name alone.

Here is the plain verdict. Renjuin has a long record in Japan, but we found no controlled human trials of the formula. Traditional use is not proof that a remedy works.

Safety, not benefit, is the main point of this page. Renjuin contains kanzo (licorice), and licorice has real, documented risks in people.

How does Renjuin work?

Kampo explains Renjuin in its own terms. It is said to move stagnant "water" and to build "blood". These are traditional ideas, not measured body chemistry.

Modern mechanism work on the whole formula is sparse. We found no studies that test how Renjuin as a blend acts in the human body.

One part is well understood. Glycyrrhizin, from kanzo (licorice), blocks an enzyme in the kidney. In people this leads the body to hold salt and water and to lose potassium.

Doctors call that pattern pseudoaldosteronism (a false hormone-like state that holds salt and drops potassium). This is a proven human effect, not a lab-only finding.

The other herbs have been looked at mainly in test tubes and animals. Peony and cnidium extracts appear to relax blood vessels in animal work. Whether that happens in people taking Renjuin is not known.

What forms does Renjuin come in?

Most people meet Renjuin as a granulated extract in sachets. Licensed Japanese makers supply it as an approved Kampo product. We could not confirm a specific maker's product number, so none is given here.

It also exists as a fine powder, as tablets, and as a decoction (herbs boiled in water). The decoction is the older form and is still used by some practitioners.

Supply outside Japan is patchy. Imported products vary in strength and in how much licorice they contain.

Where it comes from:

Renjuin is a Japanese formula built from two Chinese classics. Ryokeijutsukanto comes from the Han-era Shang Han Lun. Shimotsuto comes from a Song-era formulary.

Japanese doctors combined the two during the Edo period. The joined formula was used for dizzy, pale, easily tired patients.

It stayed in use and is now an approved Kampo formula in Japan's health system.

What does Renjuin help with?

• Dizziness and lightheadedness: This is the classic Kampo use. The formula is picked for people who feel unsteady and washed out. We found no controlled trial testing Renjuin for dizziness.
• Palpitations (a pounding or fluttering heartbeat): Ryokeijutsukanto, one half of the blend, is traditionally used for this feeling. New or severe palpitations need a doctor first. No trial supports Renjuin for this.
• Dizziness on standing up: Kampo practice uses Renjuin for people who go grey or swim-headed when they rise. Trial evidence is absent. Low blood pressure and anaemia should be ruled out by a doctor.
• Tiredness with pale skin: Shimotsuto, the other half, is the classic "blood-building" formula in Kampo. This is a traditional idea, not proof of an effect on blood counts. Pale skin with tiredness may mean anaemia, which needs testing.
• Period-related dizziness and fatigue: Renjuin is often chosen for women with light-headedness around their period. The use is traditional and widely reported by Kampo doctors. We found no controlled trials.
• Cold hands and feet: Kampo links cold limbs with weak "blood" and uses shimotsuto-type formulas for it. Evidence is limited to traditional practice and case reports.

Which foods are rich in Renjuin?

1. Licorice sweets: they hold the same glycyrrhizin as kanzo
2. Licorice root tea: adds to your total licorice load
3. Licorice-flavoured confectionery and some herbal candies: small amounts that still add up

Practical Tips:

Licorice from food counts towards the same risk as the licorice in this formula.

What are the side effects of Renjuin?

• Stomach upset, nausea or poor appetite
• Loose stools or diarrhoea
• Swollen ankles or puffy face from held fluid
• Weight gain over days from held fluid
• A rise in blood pressure
• Low potassium, causing muscle weakness, cramps or numbness
• Muscle damage, with aching muscles and dark urine
• An irregular or thumping heartbeat
• Rash or itching
• Rare liver injury, with yellow skin or eyes
• Rare lung inflammation, with dry cough, fever and breathlessness

Good to know:

Most side effects are mild. Stomach upset, poor appetite and loose stools are the usual complaints. They often come from the jio and toki in the blend.

The serious risk comes from the kanzo (licorice). Its glycyrrhizin can cause pseudoaldosteronism (a false hormone-like state that holds salt and drops potassium).

That state shows up as swelling, weight gain, rising blood pressure and weak muscles. In bad cases the muscles break down and the heartbeat turns irregular.

The risk is higher with larger amounts and longer use. Older people, women and people on water tablets are more prone. This is why a prescriber, not the user, sets the amount and checks blood potassium.

Rare reactions are also reported with Kampo formulas of this type. They include liver injury and lung inflammation. Both need a doctor straight away.

How much Renjuin should you take?

• Recommended daily: No self-treatment amount is set for Renjuin, and this page does not give one. In Japan a Kampo doctor or pharmacist sets the amount. That is the safe way to use it, because the licorice content must be counted. Tell your prescriber about every other herbal product you take. Many Kampo formulas contain kanzo (licorice), and the amounts add up.
• Best time of day: Kampo granules are usually taken before meals or between meals. Warm water is the traditional way to take them. Follow the timing your prescriber gives you.
• With or without food: Usually on an empty stomach, with warm water. Jio and toki can upset the stomach in some people. If that happens, taking it with food is common practice.
• Time to effect: Not established, because no trials exist. Kampo practice expects some change within days to a few weeks. If nothing has changed in a month, ask your prescriber to review it.
• How long to take it: Short courses are safer than long ones. Ask for a review within about four weeks. Longer use raises the risk from licorice. If you keep taking it, your doctor should check your blood pressure, your weight and your blood potassium. Stop and seek advice if your ankles swell or your muscles feel weak.