Educational information, not medical advice — ask your doctor or midwife.
Roselle is a tropical shrub with fleshy red flower cups. Dried, those cups make the tart red drink sold as hibiscus tea or karkadé. It is used as a food, a tea and a supplement.
People drink it for raised blood pressure, for mild fluid build-up, and simply as a sour cooling drink. Here is the evidence verdict in one line: small human trials show a modest drop in blood pressure, and little else is solid.
Long use in a tradition is not proof that a remedy works. It is also not proof that it is safe. Roselle has both a folk record and some real trial data, and this page keeps the two apart.
Short answer: the blood pressure effect has been measured in people, but the reason for it is not settled.
In animal studies, roselle extracts act like a mild water pill (diuretic). They also appear to block ACE, an enzyme that tightens blood vessels. Whether this is what happens in people drinking the tea has not been shown.
In cell and test tube studies, the red pigments mop up free radicals. Roselle acids appear to relax blood vessel walls in animal tissue. These are laboratory findings, not proven effects in your body.
Lab work also points to effects on blood fats and blood sugar handling. Human results on both are weak and mixed.
Dried flower cups, loose or in tea bags, are the form most people meet.
They are steeped in hot water, or soaked in cold water for a smoother, less sharp drink.
Bottled hibiscus drinks and cordials are sold in shops. Sugar content in these can be high.
Capsules and tablets hold a dried extract. A few are standardised to anthocyanin content.
You will also find roselle as jam, syrup, a natural food colour, and a base in fruit tea blends. It is common in blends marketed for "cleansing" or "detox".
Roselle came to Europe through trade, not from a European hedgerow. Its home range is Africa, and older use there and in the Middle East is far wider.
In Europe it settled in as karkadé. Italian households drank it through the 1930s, when imported black tea was scarce. It stayed popular as a sour red tea in Italy, Germany and parts of eastern Europe.
European folk use treated it as a cooling drink in heat and fever. Herbalists also gave it for sluggish digestion and for mild puffiness in the legs.
Some older texts listed it as a drink to bring on a late period. That use is the reason pregnancy warnings appear on this page.
Stop and see a doctor if you feel dizzy, faint or oddly tired after starting it, especially if you take blood pressure tablets.
See a doctor promptly if you notice yellow skin or eyes, dark urine, or pain under your right ribs.
Get urgent help for a rash with swelling of the lips, tongue or throat, or any trouble breathing.
Tell your doctor before surgery, and tell them if your home blood pressure readings swing after starting roselle.
In the UK, EU and US, roselle is an ordinary food and beverage plant. It is also sold as a food supplement.
No medicines regulator has approved it to treat or prevent any disease. Supplement makers are not allowed to claim it does.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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