There is sparse safety, quality, and toxicity data available for tongkat ali from human studies, along with a lack of standard criteria and regulation for its commercial preparations. Some studies have raised concerns about the possible contamination of herbal preparations of tongkat ali by heavy metals in Malaysia, including levels of lead and mercury above permissible limits.[1][2][3]
Safety and toxicity studies in rodents have found that the LD50 for tongkat ali (the dose that, when administered all at once, causes death in 50% of test animals) is greater than 3,000 mg/kg for the aqueous extract and between 1,500–2,000 mg/kg for the alcoholic extract.[4] Pathological changes in the liver were observed in rats at a dose of 1,200 mg/kg, corresponding to a 1,200 mg daily dose in humans.[5] However, tongkat ali has been shown to be safe for the liver in humans.[6]
Studies using a dosage of 200–600 mg/day in humans have noted minor side effects, including gastrointestinal symptoms and itching.[6] Otherwise, adverse effects seem to be rare.[7] Tongkat ali is not recommended for pregnant and lactating women; men with breast or prostate cancer, diabetes, heart disease, kidney disease, liver disease, or sleep apnea; and children, due to a lack of data in these populations.[8][9]
Tongkat ali may impede the actions of propranolol, a medication used to treat high blood pressure (hypertension), by interfering with its absorption and bioavailability.[10] Anyone using this medication and considering supplementing with tongkat ali should first consult a healthcare professional.