Does it work?
Hibiscus (Hibiscus spp.) has been used for centuries by Ayurvedic (Hindu) and Chinese medical practitioners. Human studies have shown that extracts of hibiscus may lower systolic and diastolic pressure. In one study, hibiscus standardized extract worked as well as captopril (Capoten®), a commonly used angiotensin converting enzyme (ACE) inhibitor, in lowering blood pressure. Additional high-quality studies comparing hibiscus to placebo are needed to confirm these results, although the use of hibiscus for hypertension looks promising.
Dangers and possible side effects....
Caution is advised when taking hibiscus, as numerous adverse effects including diuresis (increased excretion of fluid) can occur. Avoid if allergic or hypersensitive to hibiscus, its constituents, or members of the Malvaceae family. Use cautiously with hypertension or hypotension. Hibiscus rosa-sinensis has exhibited antifertility activity, and the benzene extract of the flower petals may suppress implantation. Use cautiously if pregnant or trying to get pregnant, or breastfeeding.