Hibiscus Tea

Last reviewed October 2026 · Based on 17 studies

Bottom line

Hibiscus tea modestly lowers blood pressure, roughly 5-8 mmHg systolic and 3-4 mmHg diastolic across pooled trials, with bigger drops in people starting higher. It also slightly lowers fasting blood sugar, and is generally well tolerated, though longer-term safety data are limited.

What it helps with

Lowers blood pressure — Benefit, evidence grade B (Moderate). Meta-analyses of randomised trials, newest with 26 trials and about 1,800 people; downgraded once because blood pressure is a surrogate marker.
Lowers fasting blood sugar — Benefit, evidence grade C (Limited). Two small meta-analyses of trials found slightly lower fasting glucose; downgraded for small samples and surrogate marker.

What it is

Hibiscus tea is a tisane brewed from the calyces of Hibiscus sabdariffa, also called sour tea, roselle or red tea [1]. The plant is rich in organic acids, polyphenols, anthocyanins and polysaccharides [2]. Trials have tested it as brewed tea drunk 2-3 times a day, as capsules or powders of dried calyx, and as bottled roselle drinks [3][4][5].

How it might work

The proposed explanation is that its polyphenols and anthocyanins relax blood vessels and act as antioxidants, though this is not proven in humans [2][5]. A trial found a salt-excreting (natriuretic) effect in the hibiscus group, which would plausibly lower pressure [4]. A single-dose study found better flow-mediated vessel dilation after hibiscus extract, a short-term sign of vessel relaxation [6].

What the research says

A 2015 meta-analysis of 5 trials (390 people) found systolic pressure down 7.58 mmHg and diastolic down 3.53 mmHg, with larger effects from higher starting pressure [2]. A 2020 meta-analysis of 7 trials (362 people) found falls of 4.71 mmHg systolic and 4.08 mmHg diastolic, plus fasting glucose down 3.67 mg/dL [7]. A 2025 umbrella review of 26 trials (1,797 people) found dose-dependent blood-pressure falls against placebo and other teas, similar on average to drugs, with credible drops over 10 mmHg in people over 50, in trials over four weeks, and in low-bias trials; it also reported lower total and LDL cholesterol, lower fasting glucose, higher HDL, and a small cholesterol-picture improvement overall [8]. A separate 2020 meta-analysis found fasting glucose down 3.96 mg/dL and LDL down 7.84 mg/dL, with no clear change in total cholesterol, HDL or triglycerides [9]. Against drugs directly, hibiscus matched captopril over 8 weeks and hydrochlorothiazide over 4 weeks, while ramipril beat it on systolic pressure over 4 weeks [10][11][4]. A strict 2021 Cochrane review counted only one small placebo-controlled trial in hypertension and called the evidence insufficient, with very uncertain estimates [1].

Doses used in studies

Brewed-tea trials mostly used 2-3 servings a day for 4-6 weeks [3][12][13]. Capsule trials used dried calyx powder such as 320 mg twice a day for 4 weeks, or roselle extract totalling 5,600 mg a day for 8 weeks [4][1]. A bottled roselle drink trial ran 200 mL a day for 6 months [5]. A hibiscus-olive product was dosed twice a day for 8 weeks [10]. These are study doses, not recommendations.

Safety and interactions

Common side effects looked minor in trials: the 2025 review found no higher risk of adverse events with hibiscus, and a 4-week trial reported no side effects [8][11]. No established upper intake limit or toxic dose was reported in the reviews read [8]. Because hibiscus lowers blood pressure, combining it with blood-pressure or water-pill medicines could lower pressure too far, so people on these drugs should talk to a doctor first [8][4]. No blood-sugar-medicine interaction data were reported, though hibiscus slightly lowers fasting glucose [7][9]. No pregnancy or breastfeeding safety data appeared in the reviews read, so pregnant or breastfeeding people should be cautious and ask a doctor [8][14]. People with low blood pressure or kidney or liver disease have no dedicated safety data; one review noted a small, clinically unimportant rise in a liver enzyme (AST) with hibiscus [8].

Caveats and open questions

Most trials were small and lasted only weeks, and the strictest review judged the evidence insufficient on its narrow criteria [1][7]. Some products mixed hibiscus with olive leaf or lemon verbena, so the hibiscus-only share of the effect is unclear [10][15]. Blood pressure is a risk marker rather than a heart attack or stroke outcome, so the hoped-for heart benefit is inferred rather than shown [8].