Tribulus terrestris

What it is

Tribulus terrestris is a small spiny plant used for centuries in Ayurvedic and traditional Chinese medicine. Today, extracts of its fruit or leaf appear in testosterone booster, bodybuilding and libido supplements.

The marketing says it raises testosterone. The honest position is that this has not held up well in human studies. Trials in healthy men have mostly found no meaningful change in testosterone, and the case for muscle gain is weak.

There is some research on sexual desire and erectile function, but it is small, short and not consistent. It is a herb with a lot of reputation and not much proof.

How it works

The proposed active compounds are saponins such as protodioscin, which were thought to stimulate the body's own luteinising hormone and so testosterone production. Animal studies suggested this, but the effect has not been reliably shown in humans.

What the evidence says

• Weak Raising testosterone levels
  Most human trials in healthy men found no meaningful increase, and any changes were small and inconsistent.
• Weak Muscle gain or athletic performance
  Trials in trained men generally show no benefit over placebo.
• Limited Libido and sexual desire
  A few small trials suggest some improvement in desire, especially in women, but quality is modest.
• Limited Erectile function
  Small studies hint at a benefit but are too limited to rely on, and it does not replace proper assessment.

Evidence ratings are our plain-English summary of how much good human research exists, not a promise of results. How we rate evidence.

Dosage and timing

• Products range widely, often from a few hundred milligrams up to over a gram a day; there is no established best dose because the effect itself is unproven.
• Many labels state a saponin percentage, so compare the amount of standardised extract rather than the headline capsule weight.
• Taking it with food may reduce stomach upset.
• Trials are typically a few weeks to a few months; if you try it, set an end date and stop if you see no change.
• Check current guidance and speak to a pharmacist if you take regular medication.

Forms and what to look for

• Standardised fruit extracts with a stated saponin or protodioscin percentage are the most common.
• Whole herb powders have unpredictable potency.
• Be careful of products listing it among many ingredients in a testosterone blend.
• Avoid products with exaggerated claims of testosterone gains.
• Look for the plant part used, the extract ratio and the saponin content.

What to expect, and when

• Studies of libido or testosterone usually run for several weeks to a few months.
• You will probably not notice anything. If you do, it is more likely a placebo effect than a hormonal one.
• If your testosterone is genuinely low, a GP blood test is a better route than a supplement.

Side effects

• Stomach upset, nausea or cramps.
• Trouble sleeping or restlessness in some people.
• Occasionally reported irritability or heavy menstrual bleeding.
• Rare case reports of liver or kidney problems and of painful enlarged breast tissue, mostly poorly documented.

Interactions

• Blood glucose-lowering medicines: Tribulus may lower blood sugar slightly, so monitor if you have diabetes.
• Blood pressure medication: possible additive lowering effect.
• Lithium: there is a theoretical effect on how the body handles it; ask a pharmacist.
• Hormonal medicines and anti-androgens: effects are unclear, so discuss with a clinician.

Who should avoid it

• Pregnant or breastfeeding people, because safety data are lacking.
• People with hormone-sensitive conditions such as prostate or breast cancer, unless a clinician agrees.
• Anyone with diabetes or low blood pressure, without medical advice.
• People with liver or kidney disease.
• Anyone about to have surgery, since it may affect blood sugar.

Risks and safety

• Some products sold as tribulus have been found in analyses to contain far less of the labelled compounds than claimed, and some sports supplements have been adulterated with undeclared steroids or stimulants.
• Tribulus itself is not on the WADA prohibited list to the best of current knowledge, but athletes have had positive tests linked to contaminated products. Check current rules.
• Self-treating low libido or suspected low testosterone can delay diagnosis of an underlying issue.

Buying well: quality and testing

• Prefer products with third-party testing such as Informed Sport or NSF Certified for Sport, especially for tested athletes.
• Look for a stated extract type and saponin percentage.
• Avoid proprietary testosterone-boosting blends that hide doses.
• Be sceptical of before-and-after photos and claims of dramatic testosterone gains.
• Check manufacturer details and batch testing.

Bottom line

Tribulus is heavily marketed on testosterone, and that is the claim with the least support. A few small studies suggest a possible effect on desire, but nothing that makes it a reliable choice. If you are worried about low libido, low energy or testosterone, a GP appointment and blood test will tell you more than a supplement will.