Benefits
Testosterone support in men with low levels
In a randomised, double blind, placebo controlled multicentre trial in 105 men aged 50 to 70, 200 mg a day of the Physta extract raised total testosterone at weeks 4, 8 and 12, with improved free testosterone and less fatigue. That trial was funded by the extract manufacturer. An older study in men with late onset hypogonadism also reported higher testosterone, but it was open label with no placebo group. Both populations were ageing men, so these results do not show what tongkat ali does in a younger man with normal testosterone.
Stress and cortisol modulation
One placebo controlled study in 63 moderately stressed adults (32 men and 31 women) reported lower cortisol, a better cortisol to testosterone ratio and improved tension, anger and confusion scores after 4 weeks. That is a single small, short, industry funded study, so treat this as preliminary rather than settled.
Muscle strength and exercise recovery
This is the weakest area on the page. A four arm randomised trial in men with age related androgen deficiency (average age 47.6) compared control, the extract alone, exercise training alone, and exercise plus the extract. The extract on its own produced no significant improvement in measured leg strength or in symptom scores versus control; the strength and fitness gains came from the exercise. The manufacturer funded Physta trial in men aged 50 to 70 did report increased muscle strength. No cited trial measured recovery from exercise.
No fertility evidence on this page
None of the studies cited on this page measured sperm count, sperm motility, semen quality or pregnancy, so nothing here supports a fertility claim. If fertility is your goal, see a doctor rather than relying on a supplement.
Energy and well-being
In the 12 week Physta trial in men aged 50 to 70, participants reported less fatigue and better quality of life alongside the hormone changes. The 4 week stress study reported better mood scores. Both outcomes are self reported, both were in ageing or stressed adults, and the larger trial was funded by the extract manufacturer.
Libido and sexual function were not measured
Tongkat ali has a long traditional reputation as a male tonic, but none of the studies cited here measured libido, erections or sexual satisfaction. A higher testosterone reading on a blood test does not automatically mean a change in sexual function, so this page makes no claim there.
Quality of extract matters significantly
Tongkat ali extracts vary dramatically in eurycomanone and eurypeptide content. Concentrated extracts require a large amount of root material, and very cheap products may contain little of the active compounds. Because the trials were run on specific standardized extracts, their results do not necessarily apply to an unstandardized product.
Branded forms (LJ100®, Physta®)
The strongest trial cited here used Physta (Biotropics Malaysia), a standardized water extract, in men aged 50 to 70. The 4 week stress study used LJ100 (HP Ingredients). Both studies were tied to the companies behind those extracts. No study cited here shows that an unbranded extract performs the same way, so treat these results as specific to the product that was tested.
Mechanism of action
SHBG inhibition and free testosterone liberation
One proposed explanation is that compounds in the root loosen how tightly SHBG (sex hormone-binding globulin) holds testosterone, leaving more of it unbound. This comes from laboratory work rather than from the human trials cited on this page, and it remains a hypothesis rather than something demonstrated in people. It also sits awkwardly with the cited trial, which reported a rise in total testosterone, not just free testosterone.
HPG axis stimulation via LH release
A second proposal is that the plant's compounds prompt the pituitary to release luteinizing hormone, which signals the testes to make testosterone. None of the human studies cited here measured luteinizing hormone, so this pathway is unconfirmed in people, and it should not be read as a favourable comparison with prescription testosterone.
5-alpha reductase and aromatase modulation
Laboratory work has also looked at whether the extract slows the enzymes that convert testosterone into DHT and into estradiol. This has not been shown in any of the human trials cited here, and those trials were in men, so nothing on this page speaks to hormone effects in women.
Clinical trials
Randomized, double-blind, placebo-controlled trial of LJ100 (200 mg/day) versus placebo in 63 moderately stressed adults for 4 weeks. Industry funded.
63 moderately stressed adults, 32 men and 31 women. 4-week intervention.
Salivary cortisol fell, the cortisol to testosterone ratio improved, and tension, anger and confusion scores improved. No adverse effects were reported. The limits matter: 63 people, only 4 weeks, men and women mixed, and industry funding. This is preliminary, not proof.
Randomised, double-blind, placebo-controlled multicentre trial of the Physta standardized water extract, 200 mg/day, in 105 men aged 50 to 70 over 12 weeks. Funded by the extract manufacturer.
105 ageing men aged 50 to 70. 12-week intervention.
Total testosterone rose significantly at weeks 4, 8 and 12 (p<0.001 at week 12), with improved free testosterone, reduced fatigue and increased muscle strength, and no safety concerns. This is the best designed study on the page. Two caveats: it was manufacturer funded, and it was run in ageing men, so it does not tell you what happens in a healthy younger man.
Randomised trial with four groups: control, Eurycoma longifolia alone, exercise training alone, and exercise plus the extract, in men with age related androgen deficiency (average age 47.6).
Men with age related androgen deficiency, average age 47.6. Four parallel groups.
The group taking the extract on its own showed no significant improvement in measured leg strength or in androgen deficiency symptoms compared with control. The improvements in strength and cardiorespiratory fitness came from the exercise training. The trial was designed specifically to separate those two things, which makes this the clearest evidence on the page that the supplement by itself does not drive performance gains.