Jihwang (Rehmannia)

The Yellow Oil of the Earth, Jihwang (Rehmannia)

The following passage is recorded in the Dongui Bogam. “生熟地黃 ○ 皆生血潤液 作煎作丸 久服爲妙” It states that both Saeng-jihwang and Suk-jihwang generate blood and moisten body fluids, meaning they are beneficial when taken long-term as a decoction or in pill form. The name 'Jihwang' comes from the fact that its underground stem is yellow. A root embodying the yellow light of the earth, that is the first impression of this medicinal herb.

However, viewing Jihwang simply as a 'tonic for nourishing blood' is a narrow understanding. Saeng-jihwang is cold and bitter, used to cool heat and the blood, whereas Suk-jihwang is sweet and mild, used to nourish yin and blood. Although they start from the same root, their characteristics change based on the processing method, much like how a person develops a different temperament with age and experience. Therefore, the belief that 'Jihwang is good for everyone' can actually be dangerous.

The prescriptions in the Dongui Bogam make this difference in temperature clear. For wasting-thirst (diabetes-like symptoms), Hwanggi-tang or Hwangryun-jihwang-tang containing Saeng-jihwang are used; for blurred vision in the elderly, Yagwang-yuksin-hwan containing Suk-jihwang is used. Ja-eum-jihwang-hwan is used for deficiency-fatigue, hematemesis, or irregular menstruation, while Saeng-jihwang-tang is used for fetal heat. Even though it is the same Jihwang, it serves a completely different purpose depending on its state, the prescription, and the dosage.

Therefore, Jihwang is not as unconditional as commonly thought. The cold nature of Saeng-jihwang can be burdensome for those with a weak spleen and stomach or frequent diarrhea, and the thick, sweet nature of Suk-jihwang can cause discomfort in those with dampness-phlegm or slow digestion. Classical texts stating that long-term intake is beneficial only hold meaning once you determine who it is suitable for. This page focuses on exactly those criteria, when, for whom, and in what form Jihwang should be appropriately used.

Summary at a Glance

Jihwang is a medicinal herb with three faces: Saeng (fresh), Geon (dried), and Suk (prepared). Since its properties and uses change according to the processing method despite starting from the same root, comparing them at a glance is the first step to understanding.

Category	Content
Origin	Hanja name: 地黃, Scientific name Rehmannia glutinosa (Gaertn.) Libosch. ex Steudel; the tuberous root of Jihwang belonging to the Scrophulariaceae family is used medicinally
Properties and Meridian Tropism	Saeng-jihwang: sweet, bitter, and cold (苦甘寒), targeting Heart, Liver, and Kidney meridians; Geon-jihwang: sweet and cool (凉), targeting Liver, Kidney, and Heart meridians; Suk-jihwang: mild and sweet, primarily used for Yin deficiency in the Lungs and Kidneys
Representative Aliases	Jisu (地髓), meaning the essence of the earth
Efficacy Recorded in Literature	Recorded in the Dongui Bogam as “生熟地黃 ○ 皆生血潤液 作煎作丸 久服爲妙”, both Saeng-jihwang and Suk-jihwang generate blood and moisten body fluids
Main Processed Products	Saeng-jihwang (Fresh Rehmannia), Geon-jihwang (Dried Rehmannia), Suk-jihwang (Prepared Rehmannia)
Combinations and Contraindications	Used in tonics for nourishing Yang or Yin; use Saeng-jihwang with caution for those with weak spleen/stomach or a tendency toward diarrhea, and Suk-jihwang with caution for those with dampness-phlegm or a tendency toward indigestion

The core point of this table is simple. While Jihwang is a 'root that nourishes blood and body fluids,' the cold and bitter Saeng-jihwang and the sweet and mild Suk-jihwang are used in entirely different situations.

Is this medicinal herb right for me?

Since the properties of Jihwang vary greatly between Saeng, Geon, and Suk despite being the same root, it is priority to choose the type that matches your constitution and symptoms. Below are the general criteria.

• Generally suitable cases: For those with a tendency toward Yin deficiency (陰虛) or Blood deficiency (血虛), such as facial flushing, dry mouth, nocturia, or heaviness in the waist and knees, and in cases where the appropriate type among Saeng-jihwang, Geon-jihwang, or Suk-jihwang is selected and taken under the prescription of a professional Korean medicine doctor.
• Cases requiring caution: For those who frequently experience heartburn, have weak digestion, or a tendency toward diarrhea, the cold and bitter nature of Saeng-jihwang may further irritate the gastrointestinal tract. Suk-jihwang may cause a feeling of heaviness or indigestion in those with a weak spleen/stomach or dampness-phlegm constitution, so caution is required in these cases as well. Those taking Western medications must check for potential drug interactions.
• Cases to avoid: This applies to those with a cold constitution who have a cold abdomen and frequent diarrhea, or cases where symptoms may worsen due to the cold nature of raw Rehmannia root (Saengjihwang). Additionally, as pregnancy and breastfeeding safety ratings from official institutions such as the Ministry of Food and Drug Safety (MFDS) could not be directly obtained through current searches, please be sure to inform your practitioner during the consultation if you are pregnant or breastfeeding. For Saengjihwang extract powder products registered on comedi.kr, patients with galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption should not use them due to the lactose content.

Practical Q&A

We have gathered the most frequently asked questions about Rehmannia root (Jihwang) heard in actual clinics. From "Can anyone take restorative herbal medicine?" to "The difference between raw and processed Rehmannia root," we provide answers based on verified facts and the criteria that should be considered during a consultation.

What is the difference between raw Rehmannia root (Saengjihwang) and processed Rehmannia root (Sukjihwang)?

They start from the same root, but their properties change depending on the processing method. Raw Rehmannia root is sweet and bitter in taste and cold in nature. It is traditionally used to cool heat, cool the blood, and support body fluids. Processed Rehmannia root is made by steaming and drying raw Rehmannia root several times with juice, refined rice wine, and ginger, making its nature mild and sweet. It is mainly used for nourishing blood and kidneys and filling the essence. Dried Rehmannia root (Geonjihwang) is raw Rehmannia root that has been dried, and its properties are close to the middle ground between raw and processed Rehmannia root.

My body is usually cold and I am prone to diarrhea; can I still use Rehmannia root?

Because raw Rehmannia root is cold in nature and has a bitter taste, it may not be suitable for those with a weak spleen and stomach or a tendency toward diarrhea. From a traditional perspective, processed Rehmannia root may cause a feeling of stuffiness or indigestion in those with a weak spleen and stomach or a damp-phlegm constitution. In such cases, the decision of whether to use Rehmannia root and which type to use must be made after evaluating your constitution and current symptoms.

I am taking Western medicine; is it okay to use Rehmannia root concurrently?

An interaction page between Rehmannia root and thyroid drugs has been identified in the KMCRIC drug interaction database. However, the specific interaction mechanism, clinical cases, or recommendation levels are not clear within the scope of this verification. Please consult your attending Korean medicine doctor regarding the concurrent use of Western medicine.

Can Rehmannia root be used during pregnancy?

The Dongui Bogam records Saengjihwang-tang for managing fetal heat, and the Korea Traditional Knowledge Portal introduces prescriptions containing processed Rehmannia root for vaginal bleeding caused by deficiency of qi and blood, kidney deficiency, or blood heat after pregnancy. However, since safety ratings at the level of modern official clinical guidelines have not been confirmed for the use of Korean herbal medicine containing Rehmannia root during pregnancy or breastfeeding, the decision must be made through a consultation.

Are Yukmijihwang-tang and Rehmannia root the same thing?

Yukmijihwang-tang is a representative prescription that uses processed Rehmannia root as the primary herb. According to the OASIS Traditional Medicine Information Portal, it consists of 15.0g of processed Rehmannia root combined with Dioscorea, Cornus officinalis, Poria, Moutan cortex, and Alisma, and is traditionally known as a prescription to fill the kidney yin. It is important to distinguish between a single medicinal herb like Rehmannia root and a prescription formulated around that herb.

Can I take Rehmannia root for a long time?

The Dongui Bogam contains records stating that taking raw or processed Rehmannia root as a decoction or pill for a long time is beneficial. However, this is a traditional description, and the duration for which it can be used varies by individual depending on their constitution, concurrent medications, and dietary habits. For safety, long-term use should be adjusted through regular consultations and status checks.

Relationship with Other Medicinal Herbs (Yakdae/Pairing)

Rehmannia root is rarely used alone. Raw Rehmannia root cools heat and the blood with its cold and bitter properties, but other herbs are needed to guide that power stably. Processed Rehmannia root is sweet and mild, focusing on nourishing blood and yin, but its sweetness can weigh down the spleen and stomach, making the pairing of herbs that help balance it important. In tradition, this combination where herbs complement each other's properties or set a direction is called "Yakdae (medicinal pair)." Let's look at the verified combinations to see what role Rehmannia root plays in various prescriptions.

• Processed Rehmannia root + Dioscorea + Cornus officinalis + Poria + Moutan cortex + Alisma — Yukmijihwang-tang: A representative prescription for nourishing kidney yin recorded in the OASIS Traditional Medicine Information Portal. It has been traditionally used to supplement kidney yin, with processed Rehmannia root as the primary herb.
• Raw Rehmannia root + Ginseng + Poria + Honey Gyeongokgo: A health-preserving restorative herbal medicine listed in the "Yangseong Yeonnyeon Yak-i" section of the Dongui Bogam. Using raw Rehmannia root as the main ingredient, it has been traditionally used to supplement deficiency and moisten blood and qi. (Source: sillokwiki "Gyeongokgo")
• Raw Rehmannia root + Coptis chinensis Hwangryunjihwang-tang: Recorded in the Dongui Bogam as a prescription to treat three types of wasting and thirst (Xiao Ke). (Source: Dongui Bogam, HanScope document ID) km-dongui-jabyeong-1::sec-002-78)
• Raw/Processed Rehmannia root + Astragalus Hwanggi-tang: A prescription in the Dongui Bogam to treat wasting and thirst (Xiao Ke), using raw/dried Rehmannia root and Astragalus together. (Source: Dongui Bogam, HanScope)
• Rehmanniae Radix Preparata + Angelica Gigas + Corni Fructus + Musk, Deer Antler, etc. Gongjindan: A representative restorative herbal medicine based on musk, deer antler, Angelica Gigas, and Corni Fructus, with Rehmanniae Radix Preparata added or subtracted depending on the symptoms. (Source: jcleelab.com "Clinical Application of Gongjindan and Gyeongokgo")

Points to verify during formulation: There is an entry for Rehmannia (Rehmannia glutinosa) in the KMCRIC Drug Interaction DB, and an interaction page with "Thyroid drugs" was identified; however, specific interaction mechanisms, clinical cases, or recommendation levels were not obtained through search snippets. If you are taking Western medicine, please be sure to mention it during your consultation.

In what form is it consumed?

The form of administration for Rehmannia varies slightly depending on whether it is raw, dried, or prepared. Traditionally, decoctions (boiled water), pills, or thick extracts (go) were most common. The Dongui Bogam also states, "作煎作丸 久服爲妙", it is beneficial to take it as a decoction or in pill form over a long period. The forms currently available in Korea are as follows:

• Tea Boiling and drinking Rehmannia alone is not common. Raw Rehmannia has a cold nature and a strong bitter taste, which can burden the stomach, while prepared Rehmannia is sweet and sticky, making it unsuitable for tea.
• Food It is not commonly used as a general food ingredient. Traditionally, it is used as a health-promoting restorative in the form of thick extracts like Gyeongokgo, which is a form of taking restorative medicine distinct from regular meals.
• Decoction (boiled water) This is the most traditional and common form. Most Rehmannia prescriptions, such as Yukmi-jihwang-tang, Hwangryeon-jihwang-tang, and Saengjihwang-tang, are administered as decoctions.
• Professional Prescription Rehmannia is mostly prescribed in combination with other medicinal herbs. Raw Rehmannia is selected to cool heat and the blood, while prepared Rehmannia is used to nourish yin and blood (滋陰補血). Since the duration and dosage vary based on individual constitution and symptoms, please inquire during your consultation.

Interactions and Safety During Use

Rehmannia has long been a central herb in prescriptions for nourishing blood and yin, but because of this, it is crucial who it is used for, in what condition, and with which other herbs. In particular, since raw Rehmannia and prepared Rehmannia have different properties, their precautions must be viewed separately.

• Saengjihwang: Due to its cold nature and bitter taste, those with a weak spleen and stomach or frequent diarrheashould exercise caution. (Health Kyunghyang "Rehmannia by Various Names")
• Rehmannia glutinosa (Processed): Although it has a sweet and mild nature, those with a weak spleen and stomach or a damp-phlegm (濕痰) constitutionmay experience a feeling of tightness or indigestion. However, as specific original text citations were not secured in this search, suitability based on constitution must be verified during consultation.
• Concurrent Use with Western Medicine: There is an entry for Rehmannia (Rehmannia glutinosa) in the KMCRIC Drug Interaction DB, and an interaction page with "Thyroid drugs" was identified. Specific interaction mechanisms, clinical cases, or recommendation levels were not confirmed via search snippets. If you are taking thyroid-related medication, please be sure to mention it before the prescription.
  • Reference: KMCRIC Drug Interaction DB, Rehmannia / Thyroid drugs
• Precautions by Formulation: According to the precautions for Raw Rehmannia Extract Powder products registered on comedi.kr (linked to the Korea Pharmaceutical Safety Center), Contains lactose As this product contains lactose, it may be contraindicated for patients with galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption.
  • Reference: comedi.kr, Rehmanniae Radix Extract Powder
• Pregnancy and Breastfeeding: In the Dongui Bogam, Saeng-jihwang-tang (Fresh Rehmannia Decoction) is recorded as a treatment for fetal heat (Taeyeol). In the Dang-gwi-gi-saeng-tang found in the Traditional Knowledge Portal, Suk-jihwang (Processed Rehmannia) is used for vaginal bleeding caused by deficiency of qi and blood, kidney deficiency, or blood heat during pregnancy. However, pregnancy and lactation ratings from modern official clinical guidelines (such as the MFDS or Korean Pharmacopoeia) were not obtained through this search. If you are pregnant or breastfeeding, please be sure to inform us during your consultation.

Verification is required. Specific interaction mechanisms and recommendation levels from KMCRIC, standard items for Jihwang (Rehmannia) as a single herb from the OASIS Traditional Medicine Information Portal, and modern official pregnancy/lactation ratings were not directly obtained in this search. When considering a prescription containing Jihwang, please inform us of any current Western medications, health functional foods, your constitution, and whether you are pregnant or breastfeeding. We will guide you toward a safe direction within the scope of available information.

If you experience these symptoms

While Jihwang is a medicinal herb used to nourish the blood and replenish yin, certain signals during intake may indicate that your body is burdened by the properties of the herb. For your safety, do not reduce the dose or ignore the following signals on your own; instead, please inform the attending Korean medicine doctor who manages your prescription.

• Diarrhea or abdominal discomfort after taking Saeng-jihwang (Fresh Rehmannia): Saeng-jihwang has a cold nature and a bitter taste, which may burden the digestive function of those with a weak spleen and stomach.
• Indigestion or a feeling of tightness after taking Suk-jihwang (Processed Rehmannia): Suk-jihwang is sweet and mild, but it may cause a feeling of tightness or indigestion in individuals with a weak spleen and stomach or a constitution prone to dampness-phlegm.
• Persistent abdominal pain, vomiting, or diarrhea during intake: If symptoms persist or worsen beyond general digestive discomfort, the suitability of the medicinal herb must be re-evaluated.
• Adverse reactions when used concurrently with existing thyroid disease medications: An interaction page between Jihwang and thyroid drugs was identified in the KMCRIC drug interaction database, but specific mechanisms, clinical cases, or recommendation levels were not confirmed. If you are taking Western medications, please be sure to consult with your medical provider.

If adverse reactions are severe or accompanied by systemic emergency signals such as difficulty breathing, decreased consciousness, or generalized rash, please use an emergency medical institution immediately.

Differences from other restorative medicines

Jihwang is just one type of restorative medicine, and not all restorative medicines work in the same way. In traditional Korean medicine, restorative medicines are broadly divided into qi-tonics (to supplement energy), blood-tonics (to nourish blood), yin-tonics (to nourish yin), and yang-tonics (to supplement yang). Jihwang is most commonly used on the boundary between nourishing blood and yin. Therefore, rather than providing a feeling of increased energy or talkativeness like ginseng or astragalus, it works to fill the moisture and blood deep within the body.

The role of Jihwang also differs from representative restorative medicines such as Gongjindan or Gyeongokgo. Gongjindan centers on musk, deer antler, and cornus officinalis, while Suk-jihwang is often added or adjusted as a supplement depending on the symptoms. Gyeongokgo uses Saeng-jihwang as a main ingredient and focuses on supplementing deficiency and moisturizing blood and qi along with ginseng, Poria cocos, and honey. In other words, depending on whether Jihwang is the primary or supporting ingredient, and whether it is Saeng-jihwang or Suk-jihwang, the properties and target patients vary greatly even under the same name of 'restorative medicine'.

Therefore, it must be decided based on the clinical context whether Jihwang is necessary and whether Saeng-jihwang or Suk-jihwang is more appropriate. For yin-deficiency symptoms such as nocturia or heaviness in the waist and knees, a kidney-tonifying prescription containing Suk-jihwang may be considered; for feelings of heat, dryness, or a tendency to bleed, Saeng-jihwang may be more appropriate. For your safety, please consult with your attending Korean medicine doctor to make a choice that fits your constitution and symptoms.

References

1. Jihwang-related evidence 1: Korea Institute of Korean Medicine official data.
2. Jihwang-related evidence 2: Korea Institute of Korean Medicine official data.
3. Jihwang-related evidence 3: Korea Institute of Korean Medicine official data.
4. Jihwang-related evidence 4: Korea Citation Index academic paper.
5. Jihwang-related evidence 5: Korea Citation Index academic paper.
6. Evidence materials related to Rehmannia 6: Korea Citation Index academic paper.
7. Evidence materials related to Rehmannia 7: jcleelab.com evidence materials.
8. Evidence materials related to Rehmannia 8: auraorientalhealing.com evidence materials.

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