Benefits
Placebo-controlled tablet trial in late pregnancy
In a double-blind trial of 192 low-risk first-time mothers, raspberry leaf tablets (1.2 g twice a day) or placebo were taken from 32 weeks of pregnancy until labor. The first stage of labor was not shorter. The second stage was about 10 minutes shorter and forceps births were less frequent (19.3% vs 30.4%), but these differences were not statistically significant. No adverse effects were reported for mothers or babies.
Observational studies of use in late pregnancy
In a retrospective study of 108 mothers and a prospective study of 91 women, the authors reported fewer labor interventions among users, but a review of the 108-mother study found no significant differences in labor length, augmentation or mode of birth. The 91-woman study's authors judged its large drop in augmentation most likely due to selection bias. A Norwegian survey of 600 women linked use to more cesarean births.
Post-meal blood sugar after a sucrose drink
In a randomized, open-label crossover study in 22 healthy adults, tea brewed from 10 g of raspberry leaf and taken with 50 g of sucrose lowered blood sugar at 15 and 30 minutes and insulin at 15 to 60 minutes, compared with sucrose alone. It had no significant effect on blood sugar when taken with glucose. This was a single-dose study with no placebo.
Traditional-use status in the European Union
The EU herbal medicines committee (HMPC) adopted a monograph accepting raspberry leaf tea and dry extract as traditional herbal medicines, based on long-standing use rather than clinical trials, for minor spasm with menstrual periods, mild inflammation in the mouth or throat (as a gargle) and mild diarrhea. It does not recommend use in pregnancy, breastfeeding or under age 18.
Knee comfort scores in a 12-week placebo-controlled trial
In a double-blind trial of 198 adults with knee osteoarthritis, a raspberry leaf extract at 200 or 400 mg a day for 12 weeks did not improve the main pain questionnaire score versus placebo. On a secondary 0 to 100 mm pain scale, 400 mg lowered pain about 7 mm more than placebo; function and quality of life scores did not differ. The extract's maker funded the trial.
Mechanism of action
Variable action on uterine muscle in the lab
In uterine tissue from rats, raspberry leaf tea and capsules caused weak contractions or partly damped contractions driven by oxytocin, and effects varied with the preparation and with pregnancy status. The researchers concluded the results do not support a direct labor-boosting action on the uterus. An older lab study reported different responses in rat and human uterine tissue. No such effect has been measured in people.
Polyphenols that may slow sugar digestion
A cup of tea from 10 g of leaf supplied about 50 mg of polyphenols, mostly ellagitannins. The researchers who measured a lower blood sugar rise after sucrose proposed that these compounds, especially ellagic acid, inhibit enzymes that break down sugars in the gut. That explanation was not tested directly in the study.
Relaxes intestinal smooth muscle in the lab
In guinea-pig intestine studied in a lab dish, a methanol extract of raspberry leaf relaxed the muscle, and at least two separate fractions of the extract were active, one with strong dose-dependent responses. This is isolated-tissue work only.
Inhibits drug-metabolizing liver enzymes in test tubes
Raspberry leaf extracts inhibited the human liver enzymes CYP1A2, CYP2D6, CYP3A4 and CYP2E1 in test-tube studies, and in rats, raspberry leaf given through pregnancy altered liver enzyme activity in adult female offspring. Whether usual intakes change drug levels in people has not been studied.
Clinical trials
Double-blind, randomized, placebo-controlled trial at a large tertiary hospital in Sydney, Australia, testing raspberry leaf tablets (2 x 1.2 g per day) taken from 32 weeks of pregnancy until labor. (Simpson et al. 2001, J Midwifery Womens Health)
192 low-risk women having their first baby, who gave birth between May 1999 and February 2000.
The tablets did not shorten the first stage of labor. The authors reported the only clinically significant findings as a shorter second stage (mean difference 9.59 minutes) and fewer forceps births (19.3% vs 30.4%); a later review notes these were not statistically significant, and no significant relationship was found between the tablets and birth outcomes. No adverse effects were found for mothers or babies.
Retrospective observational comparison of women who did and did not take raspberry leaf products during pregnancy, at Westmead Hospital, Australia. (Parsons et al. 1999, Aust Coll Midwives Inc J)
108 mothers who gave birth between January and July 1998; 57 had taken raspberry leaf products and 51 had not.
The authors reported shorter labor, fewer pre-term and post-term births, and fewer artificial ruptures of membranes, cesarean, forceps or vacuum births among users, with no side effects identified. A 2021 systematic review of the full paper reported no differences between the groups in gestation, labor augmentation, epidural use, length of any stage of labor or mode of birth. Women chose for themselves whether to use raspberry leaf and were not randomized.
Prospective observational cohort linking questionnaires on herbal use to maternity clinical records, analyzed with Bayesian regression, in one Australian jurisdiction. (Bowman et al. 2024, BMC Complement Med Ther)
91 women with complete records: 44 who used raspberry leaf (mostly tea, mean 2 cups a day, on average from 36 weeks) and 47 who did not.
Labor was augmented in 1 of 44 users (2%) versus 32 of 47 non-users (68%), and users had fewer epidurals and instrumental births. The authors judged an effect this large implausible as a direct herbal effect and most likely due to selection bias, said the results cannot be generalized, and said the lack of safety concerns is not evidence of safety.
Structured interviews within five days after delivery plus review of medical birth charts at Stavanger University Hospital, Norway. (Nordeng et al. 2011, Complement Ther Clin Pract)
600 women who had just given birth; 39.7% reported using herbal products during pregnancy.
Raspberry leaf use was significantly associated with cesarean delivery. This was an observational association with no control over why women chose the herb, and a later review judged it unreliable because of the small sample, selection bias, unmanaged confounders and missing dose details.
Randomized, open-label, four-session crossover study of 50 g of sucrose or glucose taken with or without tea brewed from 10 g of raspberry leaf. (Alkhudaydi et al. 2025, Nutrients)
22 healthy adults (12 men, 10 women) aged 22 to 62 in the United Kingdom.
With sucrose, the tea lowered blood glucose by 1.19 mmol/L at 15 minutes and 2.03 mmol/L at 30 minutes, and insulin at 15, 30 and 60 minutes, versus sucrose alone. With glucose, there were no significant differences. Single doses only, no placebo and no blinding; the authors list the small sample as a limitation.
Randomized, double-blind, placebo-controlled, single-center phase II trial of one capsule a day of an ethanolic raspberry leaf extract (200 or 400 mg, standardized to polyphenols) or maltodextrin placebo for 12 weeks, run by a contract research organization in Cork, Ireland, and funded by the extract's maker. (Henrotin et al. 2022, BMC Musculoskelet Disord)
198 adults aged 30 to 75 with knee osteoarthritis confirmed on X-ray (intention-to-treat population).
The primary outcome, WOMAC pain score, fell in all groups with no difference between extract and placebo. On the secondary visual analog pain scale, 400 mg reduced pain by 7.09 mm more than placebo at 12 weeks (p = 0.017); 200 mg did not differ significantly. WOMAC global, stiffness and function scores, SF-36, physical performance and activity did not differ from placebo. Three of 135 people on the extract stopped because of digestive side effects, and no serious adverse events were judged related to the product.