Drinking guava leaf tea can offer several health benefits, yet overconsumption may lead to unwanted side effects. Guava leaves are high in tannins, which in large amounts can irritate the digestive tract, causing symptoms such as nausea, bloating, constipation, or abdominal discomfort — especially for those with sensitive digestion. (Sources note digestive issues and stomach upset in excessive use.)

Since the liver and kidneys metabolize many of the bioactive compounds in guava leaves, excessive intake over time may place strain on these organs. Some animal studies suggest that very high chronic dosages of guava leaf extract can cause liver toxicity. For individuals with preexisting liver or kidney conditions, this may lead to fatigue or decreased detoxification capacity.

One of the well-known benefits of guava leaf tea is its ability to help regulate blood sugar. However, when consumed in excess, it may lower blood sugar too far in people using insulin or other antidiabetic medications, causing symptoms like dizziness, shakiness, or fainting. Guava leaf tea may also interact with medications for diabetes, hypertension, or anticoagulation, either amplifying or reducing their effects, so caution and medical oversight are advised.

When used mindfully, guava leaf tea can contribute to digestive support, mild anti-inflammatory and antioxidant effects, and aid in managing cholesterol and blood sugar levels. To reduce risks, it’s generally recommended to limit intake to 1–2 cups per day (no more than 3), avoid use during pregnancy or breastfeeding without professional guidance, and always consult a healthcare provider if you have underlying health conditions or take regular medications.