Bitter melon may help diabetics lower their blood sugar levels, and proponents claim it may help with other conditions as well, including cancer and psoriasis. However, the evidence isn't strong enough to support its use for these conditions, so the Cleveland Clinic doesn't recommend it due to potential safety concerns.
Eating bitter melon or taking bitter melon supplements could cause headaches and gastrointestinal symptoms such as diarrhea, abdominal pain, vomiting and nausea, especially if you take large amounts. It's especially important to avoid eating bitter melon seeds, as these may cause abdominal pain, fever, headache and even coma.
Avoid taking bitter melon if you take medications that lower your blood sugar levels, as it can increase the effect of these medications and cause your blood sugar to become dangerously low. It can also interact with some chemotherapy medications as well as paclitaxel and vinblastine. Check with your doctor before taking bitter melon supplements so you can avoid any dangerous medication interactions.
Other Safety Issues
The Memorial Sloan Kettering Cancer Center notes that case studies show a potential for more serious adverse effects. For example, a 22-year-old man who ate bitter melon and drank bitter melon juice three times per day for two days developed an irregular heartbeat, and a 40-year-old man who drank half a liter of homemade bitter melon extract developed stomach ulcers and needed a blood transfusion and medication to relieve his symptoms. Because it isn't clear what component in bitter melon is responsible for its effects, it isn't possible to determine standard dosages, making it easier for people to accidentally take too much and making adverse effects more likely. The University of Colorado in Denver recommends not using bitter melon for more than four weeks to limit the risk for adverse effects.
For some people, it's particularly dangerous to use bitter melon. Pregnant women and women who want to become pregnant shouldn't use bitter melon because it can bring on menstruation and cause an abortion. The red arils that surround the seeds of the bitter melon are toxic to children, potentially causing diarrhea, vomiting and death. People with liver problems and those who have a genetic disorder called glucose-6-phosphate dehydrogenase deficiency should also avoid using bitter melon.