One of the better-evidenced herbs — it lowers cortisol and SHBG, lifting free testosterone, especially in stressed or older men.
Tongkat ali (Eurycoma longifolia), or 'Malaysian ginseng', is a root extract traditionally used for energy, libido and vitality. Its active quassinoids — chiefly eurycomanone — appear to work two ways: lowering cortisol (the stress hormone that suppresses testosterone) and lowering SHBG, the protein that binds testosterone and keeps it out of action. The result is more free, usable testosterone, particularly when stress or age has knocked it down.
For a herb, the evidence is unusually decent. In moderately stressed adults, a standardised extract at 200 mg/day for four weeks lowered cortisol and raised testosterone while improving mood. In men with late-onset (age-related) low testosterone, 200 mg/day for a month improved symptoms and normalised testosterone in a large share of them. The honest caveats: many studies are short, modest in size, and run by groups tied to the supplement industry — but the direction and mechanism are consistent. It's most useful when you're stressed or older, less so if your levels are already robust.
Stressed men, older men with age-related decline, and anyone whose free testosterone is held down by high SHBG. It is not a substitute for medical testosterone therapy if you're clinically low.
Use 200–400 mg/day of a standardised water-soluble extract (standardised to roughly 1–2% eurycomanone). Doubling the dose hasn't been shown to double the benefit. There's no formal upper limit; the water extract has a strong safety record, but most evidence is for short-to-medium-term use, so periodic breaks are sensible.
Take it in the morning or early afternoon — it can be mildly stimulating and may disturb sleep if taken late. Food isn't required. Allow four weeks or more to judge the effect.
The most common complaint is restlessness or insomnia, usually from dosing too late or too high. Cut the dose or move it earlier if that happens.
It pairs logically with ashwagandha (another cortisol-lowering adaptogen) and with the zinc and magnesium foundation. Go gently if stacking several stimulating supplements.
Because it influences hormones, anyone with a hormone-sensitive condition should be cautious. It may also stimulate the immune system, so take care with immunosuppressant medication. Check with your doctor if you take any prescription medicine.
Men with hormone-sensitive conditions, anyone on immunosuppressants, and anyone pregnant or breastfeeding (avoid). Quality matters for safety too — see below.
Choose a standardised hot-water root extract with a stated eurycomanone percentage — avoid vague '1:200 extract ratio' products with no active-compound information. Crucially, buy from brands that third-party test for heavy metals, since cheap, unstandardised tongkat ali has been found contaminated with lead or mercury.
Tongkat ali is among the more credible herbal options for free testosterone, working through cortisol and SHBG, and it shines in stressed or older men. Use 200–400 mg/day of a standardised, heavy-metal-tested water extract, take it earlier in the day, and cycle in breaks.
Talbott et al., J Int Soc Sports Nutr (2013); Tambi et al., Andrologia (2012); Ismail et al., Physta RCT (2012); Examine.com — Eurycoma longifolia.
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Based on guidance from the NHS, NICE, Cleveland Clinic and peer-reviewed research.
General information, not a substitute for personal medical advice — always consult your doctor or a qualified health professional before making health decisions. If you are pregnant, breastfeeding, trying to conceive, under 18, or taking medication, speak to your doctor before starting any supplement.