Herb

Rou Gui

Cassia bark | 肉桂

Also known as:

Cinnamon Bark

Parts Used

Bark (皮 pí / 树皮 shù pí)

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

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About This Herb

Traditional Chinese Medicine background and properties

Herb Description

Cinnamon bark is one of the most powerful warming herbs in Chinese medicine, prized for strengthening the body's core warmth and circulation. It is commonly used for people who feel deeply cold, have low back pain, cold hands and feet, poor circulation, or painful periods caused by cold. In small doses, it also helps boost the body's vitality when added to tonifying formulas.

Herb Category

Main Actions

  • Tonifies Kidney Yang
  • Guides Fire Back to Its Source
  • Dispels Cold and Alleviates Pain
  • Warms the Channels and Disperses Cold
  • Tonifies Qi and Generates Blood

How These Actions Work

'Supplements Fire and assists Yang' (补火助阳) means Rou Gui powerfully strengthens the body's warming, activating force, particularly in the Kidneys. In TCM, the Kidneys house the 'Gate of Vitality' (Mingmen), the root source of all warming and metabolic activity. When this fire weakens, people experience deep cold in the limbs, low back weakness, low libido, frequent pale urination, and chronic fatigue. Rou Gui is one of the key herbs for reigniting this foundational warmth. It works gently and persistently rather than explosively, making it suitable for chronic deficiency rather than acute collapse.

'Leads Fire back to its source' (引火归元) is one of Rou Gui's most distinctive actions. When the Kidneys are too weak to anchor Yang, it can 'float upward' and produce misleading signs of heat in the upper body: a flushed face, sore throat, mouth sores, or red eyes, while the lower body remains cold. This is called 'false heat above, true cold below.' Rou Gui draws this displaced warmth back down to the Kidneys where it belongs. This is why a warming herb like Rou Gui can paradoxically resolve what looks like heat.

'Disperses Cold and stops pain' (散寒止痛) refers to Rou Gui's ability to drive out deep, stubborn cold that causes pain. Cold makes things contract and stagnate, leading to cramping abdominal pain, cold stomach discomfort, or aching joints. Rou Gui's hot, pungent nature penetrates deeply to warm the interior and relieve this type of pain. Even used alone as a powder dissolved in warm water, it can rapidly warm a cold stomach.

'Warms and unblocks the channels and vessels' (温通经脉) means Rou Gui enters the blood level and restores circulation where cold has caused stagnation. This is especially relevant for painful periods from cold stagnation, cold-type hernial pain, joint pain from cold-damp obstruction, and yin-type abscesses (deep, pale, slow-healing sores) where blood flow is blocked by cold.

'Encourages the generation of Qi and Blood' (鼓舞气血生长) refers to a subtle but important use: when added in small amounts to tonifying formulas for patients with chronic weakness and depleted Qi and Blood, Rou Gui acts like a spark that reinvigorates the body's production of these vital substances. It catalyzes the effectiveness of other tonic herbs.

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony that reveal what's out of balance in the body. Rou Gui is traditionally associated with these specific patterns.

The following describes this herb's classification within Traditional Chinese Medicine theory and is provided for educational purposes only.

Why Rou Gui addresses this pattern

Rou Gui is one of the premier herbs for Kidney Yang Deficiency because its hot, sweet, and pungent nature directly enters the Kidney channel and powerfully supplements the Mingmen Fire (the fundamental warming force housed in the Kidneys). When Kidney Yang is deficient, the body loses its ability to warm itself and metabolize fluids. Rou Gui reignites this foundational fire gently but persistently, restoring warmth to the lower back and limbs, supporting reproductive function, and strengthening the Kidneys' ability to grasp Qi for normal breathing. Its action is gentler and more sustained than Fu Zi (Aconite), making it well-suited for chronic Kidney Yang depletion.

A practitioner would look for one or more of these signs

Cold Limbs

Persistent coldness of the hands and feet, especially the lower limbs

Lower Back Pain

Chronic soreness and cold sensation in the lower back and knees

Impotence

Reduced libido, erectile dysfunction, or cold uterus with infertility

Frequent Urination

Clear, copious urination, worse at night

Shortness Of Breath

Wheezing or breathlessness due to failure of the Kidneys to grasp Qi

TCM Properties

Temperature

Hot

Taste

Acrid / Pungent (辛 xīn), Sweet (甘 gān)

Channels Entered
Heart Liver Spleen Kidneys
Parts Used

Bark (皮 pí / 树皮 shù pí)

This is partial information on the herb's TCM properties. More detailed information is available on the herb's dedicated page

Product Details

Manufacturing, supplier, and product specifications

Product Type

Granules

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Botanical & Sourcing

Quality Indicators

High-quality Rou Gui bark should be thick, heavy, and oily to the touch. The outer surface ranges from greyish-brown to dark reddish-brown, while the inner surface and cross-section should be a deep reddish-brown colour. When broken, the fracture should appear granular and oily rather than fibrous or dry. The aroma should be intensely fragrant, warm, and sweet. The taste should be sweet and pungent first, then warming, with a slightly numbing sensation on the tongue, and should not be bitter or astringent. The best grade ('Qi Bian Gui') comes in flat, thick slabs with smooth inner surfaces. When a small piece is chewed, it should produce a strong, lingering warmth. Avoid bark that is thin, dry, pale, fibrous, or lacking in aroma, as these indicate poor quality or old stock. Oil content (cinnamaldehyde) should ideally be above 2%.

Primary Growing Regions

The premier producing regions (道地药材) for Rou Gui are in southern China, particularly Guangxi Province (especially Fangchenggang, Qinzhou, and Yulin areas) and Guangdong Province (especially Zhaoqing and Luoding). Guangxi is the most important production base for high-quality medicinal cinnamon bark. Other producing regions include Yunnan, Fujian, and Hainan provinces. The herb is also cultivated throughout Southeast Asia including Vietnam and Indonesia, though Chinese-sourced material, especially from Guangxi, is considered the standard for medicinal use.

Harvesting Season

Autumn (August to October), when the essential oil content in the bark is at its peak. Trees are typically harvested after 5 to 6 years for thinner bark grades (Guan Gui), or after 10 or more years for thicker, higher-quality grades (Qi Bian Gui, Ban Gui).

Supplier Information

Treasure of the East

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Usage & Safety

How to use this herb and important safety information

Important Medical Disclaimer

The information provided here is for educational purposes only and is not intended as medical advice or to replace consultation with a qualified healthcare professional. This herb is a dietary supplement and has not been evaluated by the FDA. It is not intended to diagnose, treat, cure, or prevent any disease.

Always consult with a qualified healthcare provider, particularly if you are pregnant, nursing, have a medical condition, or are taking other medications. Discontinue use and consult your healthcare provider if you experience any adverse reactions.

Recommended Dosage

Instructions for safe storage and consumption

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Traditional Dosage Reference

Standard

1-5g

Maximum

Up to 10g in severe Yang collapse or entrenched cold conditions, under close practitioner supervision. Standard upper limit for routine use is 5g.

Notes

Use lower doses (1-2g) when adding Rou Gui as an assistant herb to warming tonification formulas, where a small amount guides other herbs and 'sparks' Yang Qi (the principle of 'a little fire generates Qi'). Use moderate doses (2-5g) for warming the middle and stopping pain, or for warming the channels to treat cold-type menstrual pain. Rou Gui is rich in volatile oils that are destroyed by prolonged boiling, so it should be added near the end of decoction (後下, hou xia), steeped separately and added to the strained decoction, or taken as a powder (0.5-1.5g per dose) swallowed or dissolved in warm water. When used as powder, the effective dose is lower because the volatile compounds are fully preserved.

Processing Methods

Processing method

Bark stripped from cultivated young trees (5-7 years old) or from the thinner branches, dried in shade and rolled into tubes. This yields thinner, less oily bark compared to mature tree bark.

How it changes properties

Guan Gui retains the same fundamental properties (hot, pungent, sweet) but is less potent than premium thick-bark Rou Gui due to lower volatile oil content. Its warming effect is milder, with less capacity to supplement Mingmen Fire. It is considered drier and better suited for warming the Middle Burner and drying dampness rather than deeply tonifying Kidney Yang.

When to use this form

When a milder warming effect is needed, such as for Spleen-Stomach cold with dampness, or when the patient cannot tolerate the full potency of thick-bark Rou Gui. Can be used at somewhat higher doses than premium Rou Gui.

Toxicity Classification

Non-toxic

Rou Gui is classified as non-toxic in the Chinese Pharmacopoeia at standard medicinal doses. However, the bark of Cinnamomum cassia contains coumarin (up to approximately 1%), which in large doses over prolonged periods can be hepatotoxic, as its metabolite (o-hydroxyphenylacetaldehyde) is harmful to liver cells. Cinnamaldehyde, the primary active component (comprising 50-60% of the volatile oil), can also be irritating in excessive amounts. Overdose or prolonged excessive consumption may cause symptoms including nausea, vomiting, dizziness, and a sensation of heat. At standard decoction doses of 1-5g, used for appropriate clinical durations, these risks are negligible. European health authorities have set limits on coumarin intake, but this primarily applies to the culinary spice consumed daily in large quantities rather than to traditional medicinal use at standard doses under practitioner guidance.

Contraindications

Avoid

Yin deficiency with Heat signs (潮热盗汗, tidal fever, night sweats, red tongue with little coating). Rou Gui is intensely hot and would further damage Yin and aggravate internal Heat.

Avoid

Excess Heat conditions (high fever, constipation, mouth sores with a full forceful pulse). The intensely hot nature of Rou Gui would worsen excess Heat.

Avoid

Active bleeding or bleeding tendency. Rou Gui invigorates Blood and warms the channels, which can worsen hemorrhage.

Avoid

Pregnancy. Classical sources note that Rou Gui can cause uterine contractions and is traditionally listed as a pregnancy caution herb (妊娠慎用). It was historically described as being able to 'move Blood and break stasis.'

Caution

Do not use together with Chi Shi Zhi (Halloysitum Rubrum). Rou Gui is listed in the classical Nineteen Mutual Fears (十九畏) as being incompatible with Chi Shi Zhi, as the mineral may adsorb the active compounds of Rou Gui and reduce its effectiveness.

Caution

Excessive menstrual bleeding or menorrhagia. Because Rou Gui warms and invigorates Blood flow, it may increase menstrual volume.

Caution

Inflammatory conditions of the throat, mouth, or pelvic area with signs of Heat. These are essentially excess or deficiency Heat patterns where adding a very hot herb would be counterproductive.

Classical Incompatibilities

Rou Gui (官桂/肉桂) fears Chi Shi Zhi (赤石脂, Halloysitum Rubrum) according to the Nineteen Mutual Fears (十九畏). The classical verse states: '官桂善能调冷气,若逢石脂便相欺' (Guan Gui is adept at regulating cold Qi, but when it meets Shi Zhi they conflict). The silicon-aluminium compounds in Chi Shi Zhi may adsorb the active volatile oils in Rou Gui, reducing its effectiveness. These two substances should generally not be used together.

Special Populations

Pregnancy

Contraindicated during pregnancy. Rou Gui is classified as a pregnancy caution herb (妊娠慎用) in the Chinese Pharmacopoeia and standard Materia Medica textbooks. Its intensely hot nature and Blood-invigorating properties pose a risk of uterine stimulation, and classical sources including the Ming Yi Bie Lu explicitly state it can 'cause miscarriage' (能堕胎). Modern pharmacological research has confirmed that cinnamaldehyde can cause uterine congestion. Pregnant women should avoid this herb entirely unless specifically prescribed by a qualified practitioner for a critical condition where the benefit clearly outweighs the risk.

Breastfeeding

Use with caution during breastfeeding. Classical sources note that cinnamon bark may affect lactation. The intensely hot and pungent nature of Rou Gui means its aromatic compounds can transfer through breast milk. While small culinary amounts are generally considered safe, medicinal doses should only be used under practitioner supervision. Nursing mothers with Heat signs or infants showing signs of Heat should avoid this herb. There is insufficient modern research specifically on Rou Gui and breastfeeding safety.

Pediatric Use

Rou Gui should be used with great caution in children. Paediatric constitutions tend toward Yang abundance and Yin insufficiency, making them more susceptible to the intensely hot nature of this herb. If indicated for genuine cold patterns in children, dosages should be significantly reduced (typically one-quarter to one-third of the adult dose for older children, and even less for infants). It is generally not suitable for children under 2 years of age. When used in children, careful monitoring for signs of Heat such as restlessness, mouth sores, or constipation is essential.

Drug Interactions

Anticoagulant and antiplatelet medications (warfarin, aspirin, heparin, clopidogrel): Rou Gui bark contains coumarin, a naturally occurring compound with blood-thinning properties. When taken alongside anticoagulant medications, this may increase the risk of bleeding. Monitoring of clotting parameters (INR) is advised if concurrent use is necessary.

Hypoglycaemic medications (insulin, metformin, sulfonylureas): Research suggests that cinnamaldehyde and other compounds in C. cassia can enhance insulin sensitivity and lower blood glucose. Concurrent use with diabetes medications could potentially cause blood sugar to drop too low (hypoglycaemia). Blood glucose monitoring should be increased if both are taken together.

Antihypertensive medications (beta-blockers, ACE inhibitors, calcium channel blockers): Cinnamaldehyde may have mild blood-pressure-lowering effects. Combination with antihypertensive drugs could theoretically cause an excessive drop in blood pressure.

Drugs metabolised by the liver (acetaminophen/paracetamol, statins): A 2025 study published in Food Chemistry: Molecular Sciences found that cinnamaldehyde activates xenobiotic receptors (PXR and AhR) that regulate drug metabolism enzymes. This means high-dose cinnamon supplementation could potentially accelerate the clearance of certain medications from the body, reducing their effectiveness. People on multiple prescription drugs should consult their healthcare provider before using Rou Gui medicinally.

Dietary Advice

While taking Rou Gui, avoid excessively cold and raw foods (such as iced drinks, raw salads, and cold fruits like watermelon), as these counteract its warming therapeutic action. Avoid spicy, greasy, or heavily fried foods when using Rou Gui for Yin-deficiency-related conditions (such as 'drawing fire back to its source'). Do not combine with excessive amounts of green tea or mung beans, which are cooling in nature and may reduce effectiveness. Foods that support the warming action include ginger, lamb, walnuts, and warm cooked grains.

Cautions & Warnings

Although this formula is typically safe for most individuals, it may cause side effects in some people. Pregnant women, nursing mothers, postpartum women, and those with liver disease should use the formula with caution.

As with any Chinese herbal remedy, it is advisable to seek guidance from a qualified TCM practitioner before beginning treatment.