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Limited evidenceMen's health

Bulbine Natalensis

A South African herb sold as a testosterone booster on the strength of rat studies. There are no human trials at all, and the same rat work flagged organ toxicity at higher doses.

Evidence last reviewed: August 2026

What the science says

  • Testosterone in rats Limited evidence

    Rat studies from a single laboratory reported that the aqueous stem extract raised serum testosterone and increased sexual behaviour over 14 days. All of the testosterone data come from rodents; no human trial has ever been published.

  • Drug interaction risk Limited evidence

    Laboratory work showed that Bulbine natalensis and its knipholone constituents inhibit CYP3A4 and CYP2C9, the enzymes that clear a large share of prescription drugs. This is in-vitro evidence, but it is the most concrete human-relevant finding available for the plant.

Dosage & safety

Studied doseNo human dose has been established. Products typically supply 325–650 mg of extract per day, which is extrapolated from rodent studies rather than tested in people.
SafetyThe same rat studies that reported androgenic effects also found raised liver and kidney markers and reduced organ weights at higher doses. Combined with the in-vitro CYP3A4/CYP2C9 inhibition, this is a plant to avoid if you take any prescription medication, have liver disease, or are pregnant or breastfeeding.

Scientific references

Where to buy

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