Hibiscus tea is made from the hibiscus flower sepals and people drink it as a hot or cold beverage. The blossom is dried and steeped to make an herbal tea that many herbalists tout as being a cure for everything from high blood pressure to flu and cold symptoms. Like many herbal remedies, however, there can be side effects.

Blood Pressure

People with low blood pressure should not drink hibiscus tea. A USDA-sponsored study done by Diane McKay of Tufts University and presented to the American Heart Association's 2008 convention, showed that people who consume hibiscus tea daily can have an average drop of 7.2 points in their systolic blood pressure. Those people who had a systolic reading of 129 or higher had a greater response to the tea. Their systolic pressure dropped by an average of 13.2 points, their diastolic pressure dropped an average of 6.4 points, and their mean arterial pressure dropped an average of 8.7 points.

Alteration of Conciousness

Hibiscus tea can, in some people, produce a hallucinogenic effect or can cause a sensation similar to intoxication. If you have never consumed hibiscus tea before, do not try it for the first time in situations where you may need to drive or where becoming sleepy or incapacitated might cause a problem or contribute to a dangerous situation.

Estrogen Issues

People with low estrogen, those who are on hormone replacement therapy, or who are using birth control pills should not drink hibiscus tea. Some studies indicate that Hibiscus rosa-sinensis may contain estrogen or may affect estrogen in some way.

Pregnancy and Breast-feeding Issues

Hibiscus is discouraged during pregnancy and breastfeeding since the potential side effects to the baby or fetus are unclear. Additionally, there is some anecdotal evidence to suggest that consuming large quantities of hibiscus tea over time may reduce fertility.

Other Precautions

Some areas of the world have traditionally used hibiscus tea to treat people with cancer, and early indicators show that there may be some basis for this use. One study conducted by Chung Shan Medical University in Taiwan showed that there are chemicals called polyphenols in hibiscus that are able to attack and neutralize cancerous cells in the brain and skin. As a result, anyone already taking anti-cancer drugs should not use hibiscus tea as it may have an additive effect on the treatment. Additionally, hibiscus tea may also affect the way acetaminophen and some other anti-inflammatories are processed by the body. To prevent a possible interaction, avoid taking the tea and anti-inflammatories within two hours of each other.