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Limited evidenceHeart & metabolic

Guava Leaf Extract

Guava leaf tea, approved in Japan as a food for specified health use for post-meal blood sugar. The supporting trials are small, old and largely from the manufacturer, so the effect on glucose is plausible but weakly established.

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What the science says

  • Post-meal blood glucose Limited evidence

    A published account of guava leaf extract tea describes human studies in which drinking it with a meal blunted the rise in blood glucose, attributed to inhibition of alpha-glucosidase and intestinal glucose transport. The trials were small and conducted by the product developer.

  • Mechanism of glucose absorption Limited evidence

    A functional assessment of Psidium guajava leaf extract confirmed inhibition of postprandial glucose absorption in laboratory and short-term testing, consistent with earlier in vitro and in vivo work on intestinal glucose transport. These are mechanistic findings, not long-term glycaemic outcomes.

Dosage & safety

Studied doseJapanese studies used guava leaf tea providing roughly 200 mg of extract taken with each meal. Capsules are commonly sold at 250–500 mg, taken with food.
SafetyGenerally well tolerated; nausea and constipation are occasionally reported. Because it can lower post-meal glucose, watch for hypoglycaemia if combined with insulin, sulfonylureas or acarbose. Not studied in pregnancy. No evidence it lowers HbA1c over time.

How to take it

TimingWith each main meal, which is how the Japanese studies dosed it.
With food?With food — the effect is on carbohydrate digestion in that meal.
Worth knowingIt only blunts the glucose rise from the meal it is taken with, so a once-daily capsule away from food does essentially nothing.

Interactions

With medications

  • insulin, sulfonylureas and acarbose

    Guava leaf blunts post-meal glucose and can add to the drug's effect. monitor your glucose and talk to your doctor before combining

With other supplements

  • other glucose-lowering supplements such as berberine or mulberry leaf

    Additive lowering of post-meal glucose. do not stack several at once

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does guava leaf tea lower blood sugar?

Guava leaf extract has limited evidence for blunting the post-meal rise in blood sugar: the human trials were small, old and mostly run by the product developer, although it is approved in Japan as a food for specified health use. There is no evidence that guava leaf lowers HbA1c over time.

When should I take guava leaf extract?

Take guava leaf extract with each main meal, as the Japanese studies did, because it only affects the glucose rise from the meal it is taken with. A once-daily capsule away from food does essentially nothing.

How much guava leaf extract per meal?

Japanese studies used guava leaf tea providing roughly 200 mg of extract with each meal. Capsules are commonly sold at 250–500 mg, taken with food.

Is guava leaf extract safe with metformin or insulin?

Guava leaf extract can add to the effect of insulin, sulfonylureas and acarbose on post-meal glucose, so monitor your glucose and talk to your doctor before combining. Avoid stacking it with other glucose-lowering supplements such as berberine or mulberry leaf.

Scientific references

Related in Heart & metabolic

Herbal medicines: what the evidence says (335)