Herb library · Herb · Psidium guajava
Guava leaf
The common Caribbean fruit tree, whose leaves and bark have long been boiled for loose bowels. One open-label trial in adults with acute diarrhea found a leaf decoction shortened recovery, and a small trial of a guava gel on mouth ulcers reported faster shrinking, but the research is thin and none of it is placebo-controlled.
Traditional use
Eaten fresh, stewed and made into jelly across the Caribbean. In Jamaica, Barham recorded in the early 1700s that the bark was very commonly given for "fluxes of the bowels", and Browne in 1756 wrote that the unripe fruit, like every other part of the tree, was astringent. Guava leaf tea is sold today, in Japan especially, to people watching their blood sugar after meals.
What studies show
- Limited
Acute diarrhea: in an open-label randomized trial in India (109 adults), a decoction of 14 guava leaves three times a day brought people back to normal in about 72 hours against 120 hours with standard care alone, with no side effects reported. A 2024 systematic review found mostly lab and animal studies and only three clinical trials, and called for more studies before the benefit and safety are settled.
- Limited
Mouth ulcers: in a single-blind randomized trial of 204 people with recurrent mouth ulcers (canker sores), a guava-based gel shrank the ulcers faster than in a group given nothing. There was no placebo gel, so the result is preliminary.
- Insufficient
Blood sugar: guava leaf extracts slow sugar uptake in lab cells and lower blood sugar in mice and rats, but the studies read for this entry include no trial in people.
Be careful of
Cautions
- InteractionGuava leaf tea is taken by people on diabetes medicines and on warfarin. A lab and rat study found it unlikely to change how the liver handles drugs or how warfarin works, but this was not tested in people. If you take medicine for blood sugar, watch for low readings and tell your clinician.
- ConditionDiarrhea in children, or with fever, blood, or signs of dehydration, needs a clinician and oral rehydration. The Indian trial gave the decoction alongside oral rehydration solution, not instead of it.
- PregnancyNo safety information for guava leaf in pregnancy or breastfeeding was found in the sources used here. The fruit as food is not the concern.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.
From the old books
What herbals and dispensaries of the past printed. History, in their words.
“Baked or stewed, they eat like English wardens, and are as red. The bark of the tree is very restringent, and very commonly given in fluxes of the bowels.”
“It bears a round fruit of a moderate size, which is much esteemed among the natives: this, while immature, is astringent, like all the other parts of the tree; but when it ripens, it is rather laxative, and then much used both in jellies and cream-dishes”
Sources
- A randomized open label efficacy clinical trial of oral guava leaf decoction in patients with acute infectious diarrhoea (J Ayurveda Integr Med, 2020) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
- Antidiarrheal effect of Psidium guajava L. extract in acute diarrhea: a systematic review (J Sci Food Agric, 2024) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
- Clinical efficacy of Psidium guajava-based herbal gel in the management of recurrent aphthous stomatitis: a randomized clinical trial (Pak J Med Sci, 2025) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
- In vitro and in vivo inhibition of intestinal glucose transport by guava (Psidium guajava) extracts (Mol Nutr Food Res, 2018) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
- Evaluation of food-drug interaction of guava leaf tea (Phytother Res, 2013) — PubMed record (opens in a new tab) · NIH · read September 25, 2026
Reviewed September 25, 2026.