Benefits
Kidney function markers in multi-herb formula trials
The human studies use Rehmannia-containing formulas, not the single herb. In a 48-week trial adding a Rehmannia-6 formula to standard care, kidney filtration declined more slowly than with standard care alone. A 24-month formula-pair trial found no overall change in a urine protein marker, with a signal only in a subgroup, while a review of formula trials reported lower urine protein but rated the evidence low quality.
Blood sugar markers when a Rehmannia formula is added to medication
Evidence is from formulas combined with standard drugs, not the single herb. A small study in older adults with type 2 diabetes added a six-herb Rehmannia formula to metformin and reported lower fasting and post-meal glucose and better insulin-resistance scores than metformin alone. It was retrospective and small, so it cannot confirm an effect of Rehmannia itself.
Menopausal symptom scores in multi-herb formula trials
A review of 17 controlled trials in women during the menopausal transition after breast cancer used formulas with Rehmannia as the main herb, compared against conventional medicine. Pooled menopausal symptom scores and immune cell ratios improved, while blood hormone levels did not change. The trials had methodological flaws and high variability, and none tested Rehmannia alone.
Bone density readings in a formula comparison trial
In a one-year trial, about 70 adults with low bone density took either a Rehmannia decoction or a standard bone medication, both on top of calcium and vitamin D. Bone mineral density at the hip and spine rose and a bone-breakdown marker fell in both groups, with no significant difference between them. There was no untreated or placebo group, so this cannot show an effect of the herb by itself.
Antioxidant activity of catalpol in laboratory and animal studies
Catalpol, the most studied compound in the root, acts as an antioxidant in cells and animals, raising protective enzymes such as superoxide dismutase and glutathione peroxidase and lowering markers of oxidative stress. In animal models of high blood sugar it also affects insulin-signaling pathways. These are laboratory and animal findings, not outcomes measured in people.
Mechanism of action
Iridoid glycosides as the main studied actives
The root's best-known compound is the iridoid glycoside catalpol, alongside related iridoids and phenylpropanoid glycosides. Reviews caution that catalpol's actions in the laboratory do not represent the whole root, whose effects depend on many compounds acting together rather than any single marker.
Antioxidant and anti-inflammatory signaling in the laboratory
In cell and animal studies, catalpol and root extracts raise antioxidant enzyme activity and dampen inflammatory signaling such as the NF-kB pathway. This is proposed as a basis for the tissue effects seen in animals, but it has not been confirmed as a clinical effect in people.
Processing changes the root's chemistry
Steaming raw Rehmannia to make the prepared root changes its taste, warmth and chemical makeup, which is why traditional practice treats raw and prepared Rehmannia as different medicines. How those chemical changes translate into different effects in people is not well defined.
Clinical trials
Randomized, assessor-blind, standard-care-controlled multicenter trial of a Rehmannia-6-based Chinese medicine granule program added to usual care for 48 weeks in adults with type 2 diabetes and chronic kidney disease with high albuminuria. (Chan et al. 2023, Clin J Am Soc Nephrol)
148 adults with type 2 diabetes, eGFR 30 to 90, and a urine albumin-to-creatinine ratio of 300 to 5000 mg/g; randomized to add-on Chinese medicine or standard care alone.
The filtration rate (eGFR) declined about 2.7 units per year less with the add-on formula than with standard care alone, a significant difference (P = 0.04). The urine albumin-to-creatinine ratio rose about 11 percent more slowly with the formula, which was not significant (P = 0.28). Adverse events were similar between groups. The treatment was a multi-herb formula, not single-herb Rehmannia.
Randomized, double-blind, placebo-controlled multicenter trial of Liuwei Dihuang pills 1.5 g/day plus Ginkgo biloba tablets 24 mg/day versus matching placebo for 24 months in type 2 diabetes without or with early kidney involvement. (Shi et al. 2019, Front Endocrinol (Lausanne))
600 adults with type 2 diabetes; 431 had urine albumin-to-creatinine data at both baseline and 24 months.
The primary outcome, change in urine albumin-to-creatinine ratio over 24 months, did not differ between groups overall. In the subgroup starting with a ratio at or above 30 mg/g, the formula-plus-Ginkgo group had a larger reduction than placebo (P < 0.05). The tested product combined a Rehmannia formula with Ginkgo, not Rehmannia alone.
Systematic review and meta-analysis of randomized trials of Liuwei Dihuang pills or decoction combined with conventional medicine versus conventional medicine alone for early diabetic kidney disease. (Du et al. 2026, Front Med (Lausanne))
11 randomized trials with 1,007 participants with early diabetic kidney disease.
The combination lowered the urinary albumin excretion rate and improved serum creatinine and blood urea nitrogen versus usual care alone, with a higher total effective rate. Heterogeneity was high and the authors rated the overall evidence quality low because trials lacked blinding and allocation concealment. Every trial used Rehmannia within a formula.
Retrospective study with random-number allocation comparing Liuwei Dihuang pills added to metformin against metformin alone in older adults with type 2 diabetes. (Li et al. 2023, Pak J Med Sci)
80 older adults with type 2 diabetes, split between metformin alone and metformin plus the six-herb Rehmannia formula.
The formula-plus-metformin group had lower fasting glucose, post-meal glucose and HbA1, better insulin-resistance and insulin-secretion scores, and lower inflammatory markers than metformin alone (all P < 0.05). Being retrospective and small, with a formula rather than single-herb Rehmannia, it cannot establish an effect of the herb itself.
Systematic review and meta-analysis of randomized trials of Chinese herbal formulas with Rehmannia glutinosa as the main herb versus conventional medicine for menopausal-transition symptoms in women treated for breast cancer. (Kong et al. 2025, Saudi Med J)
17 randomized trials with 1,139 women in the menopausal transition after breast cancer treatment.
Pooled menopausal symptom (Kupperman) scores improved and immune cell ratios (CD4/CD8) rose with the Rehmannia-based formulas compared with conventional medicine, while blood hormone levels did not change and a cancer-therapy quality-of-life score was no different. The authors noted methodological flaws and high heterogeneity, and no trial tested Rehmannia alone.
Randomized trial comparing an oral Rehmannia (Dihuang) decoction with alendronate for one year, both on top of calcium and calcitriol, in adults with low bone density. (Wan et al. 2019, Zhongguo Gu Shang)
72 adults with primary low bone density, randomized to the Rehmannia decoction or alendronate; both groups also took calcium and vitamin D.
Over one year, bone mineral density at the hip and spine rose and a bone-breakdown marker fell within both groups, with no significant difference between the decoction and the bone medication. There was no placebo or untreated group, so the shared improvement cannot be attributed to the herb. Published in Chinese.