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Overview: Rehmannia is a plant called Rehmannia glutinosa. Its root is used in traditional Chinese medicine, either raw or after processing, and is often combined with other herbs in prepared formulas. People take rehmannia for many reasons, including blood sugar support, menopausal symptoms, memory and thinking, and kidney health, but these benefits are not well defined. Common side effects include stomach upset or digestive problems. Before taking rehmannia, make sure to tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is rehmannia used for?

Rehmannia (Rehmannia glutinosa) is commonly used for the following reasons, despite limited research and its benefits not being well defined.

Rehmannia is also used for other purposes, such as supporting the immune system, the liver, and general wellness. The benefits of rehmannia for these and other uses are not well defined.

Note: The FDA has not reviewed rehmannia for safety and effectiveness. Learn more about dietary supplements here.

How does rehmannia work (mechanism of action)?

Rehmannia comes from a plant called Rehmannia glutinosa, also known as Chinese foxglove. The root is the part used to make supplements. In traditional Chinese medicine, the root is used in two main forms: a raw (unprocessed) form and a processed form prepared by a special cooking and drying process. The two forms are used for different purposes and have somewhat different chemical makeups. Rehmannia is often sold in products that combine it with other herbs, such as the traditional formula Liuwei Dihuang.

Rehmannia root naturally contains many chemicals. The ones studied most are a group called iridoid glycosides (the main one is catalpol), large sugar molecules called polysaccharides, and phenylethanoid glycosides (such as acteoside). In laboratory and animal research, catalpol appears to lower blood sugar levels and reduce insulin resistance by acting on cell pathways involved in energy use and inflammation. In laboratory and animal research, rehmannia polysaccharides appear to affect the immune system and reduce inflammation. These effects have mostly been seen in the laboratory or in animals, not in well-designed human studies. A review of Chinese herbal medicine for menopausal symptoms did not find good evidence that rehmannia works better than a placebo containing no medicine.

Some clinical trials found that formulas containing rehmannia may reduce protein in the urine in people with diabetes-related kidney disease or other forms of chronic kidney disease. Because rehmannia was used alongside other treatments in these studies, it is not clear how much rehmannia itself contributed to these effects.

The benefits of rehmannia are not well defined. Most of what is known comes from traditional use and from laboratory or animal research. Much of the human research has used herbal formulas that combine rehmannia with other herbs, so the effect of rehmannia on its own is not clear.

Herbal products, such as rehmannia, naturally contain many different chemicals. The amounts of each chemical in a specific rehmannia product may vary. Some, none, or all of these chemicals may have effects on the body. These effects may change depending on how much of each chemical is found in the product you are using.

How should I store rehmannia?

You should store rehmannia according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of rehmannia?

The most common side effects of rehmannia are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. There is not a lot of research on its side effects when rehmannia is used by itself. Tell your health care provider if you have side effects that bother you.

  • Loose stools or diarrhea
  • Abdominal fullness or bloating
  • Reduced appetite

There may be other side effects of rehmannia that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of rehmannia?

While less common, the most serious side effects of rehmannia are described below, along with what to do if they happen.

Severe Allergic Reactions. Rehmannia may cause allergic reactions, which can be serious. Stop taking rehmannia and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Liver Problems. Traditional Chinese medicine products, including some that contain rehmannia, have rarely been linked to liver injury. This may be caused by the herbs themselves, by taking large amounts, or by products that are contaminated or mislabeled. Stop taking rehmannia and contact your health care provider right away if you have any of the following signs of a liver problem.

  • Yellowing of the skin or the white part of the eyes (jaundice)
  • Dark urine
  • Pale-colored stools
  • Pain in the upper right part of the belly
  • Nausea, vomiting, or loss of appetite that does not go away
  • Unusual tiredness or weakness

Warnings & Precautions

Who should not use rehmannia?

Allergies to Ingredients. People who are allergic to any of the following should not take rehmannia.

  • Chinese foxglove
  • Rehmannia
  • Rehmannia glutinosa
  • Rehmanniae radix
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific rehmannia products they stock.

What should I know about rehmannia before using it?

Rehmannia is a dietary supplement. It cannot be marketed to treat or cure a disease.

Rehmannia is available in many forms. Common forms include dried root slices, powders, teas and decoctions (boiled preparations), tinctures (liquid extracts), and capsules. It is often sold in products that combine it with other herbs, such as the traditional formula Liuwei Dihuang. Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

If you use a powder, follow the label for how to measure a dose, usually by a scoop or by weight in grams. If you use a liquid extract or tincture, follow the label for how to measure a dose, usually with the dropper provided.

Traditional Chinese medicine products have sometimes been found to be contaminated with heavy metals, medicines, or other herbs or mislabeled. In rare cases, herbal products, including some that contain rehmannia, have been linked to liver injury. Choose products from a maker you trust, and tell your health care provider if you have liver disease or signs of a liver problem (see the Side Effects section for more details).

Keep rehmannia out of the reach of children.

Herbal products, such as rehmannia, naturally contain many different chemicals. The amount of each chemical in a specific rehmannia product can change for many reasons, including the area where the plant was grown, the weather during growth, the time of year when it was harvested, and the way that the plant was processed after it was harvested. If you switch to a new bottle or a different brand, you may not have the same effects or side effects because of this variability. Talk to your health care provider if you have questions or concerns.

The FDA has not tested rehmannia products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using rehmannia?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. Sharing this information will help your health care provider know if this or other supplements are right for you.

In particular, make sure that you discuss any of the following.

Diabetes and Low Blood Sugar. In laboratory and animal research, rehmannia may lower blood sugar. It is not known if rehmannia affects blood sugar levels in people. If you have diabetes or take medicine to manage your blood sugar, talk to your health care provider before taking rehmannia.

Liver Problems. Some herbal products, including certain traditional Chinese medicine products, have rarely been linked to liver injury. If you have liver problems, talk to your health care provider before taking rehmannia.

Digestive Problems. Rehmannia may cause digestive upset, such as loose stools. If you have ongoing digestive problems, talk to your health care provider before taking rehmannia.

Other Medicines and Supplements. Before taking rehmannia, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how rehmannia could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if rehmannia passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does rehmannia interact with foods or drinks?

There are no known interactions between rehmannia and foods or drinks.

It is unknown if drinking alcohol will affect rehmannia. Because both alcohol and some herbal products, including rehmannia, may affect the liver, it may be best to limit alcohol while taking rehmannia.

Does rehmannia interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using so they can watch for any potential interactions.

In particular, make sure that you discuss if you are using any of the following before taking rehmannia.

  • A medicine for diabetes
  • A medicine for blood pressure

The interactions between rehmannia and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with rehmannia is incomplete. Always check with your health care provider before taking rehmannia with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much rehmannia?

If you or someone else has used too much rehmannia, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Rehmannia is available in various forms, and it is often combined with other herbs. Read the product label closely, and take rehmannia only as directed on the label or by your health care provider. Do not take double or extra doses to make up for a missed dose.