A reference work, not a recommendation to use: this profile describes mechanism and evidence and does not replace medical advice. The claims come from marketing and forums and are tested here, not endorsed.

Claims checked

  • Testosterone ↑ in healthy men

    Mixed results

    Testosterone & hormones · healthy · Human, randomised

    In the meta-analysis, the pooled effect in men with normal testosterone was not significant (3 RCTs, 88 participants, very high heterogeneity) [4]. One small RCT in young men found an increase [3], another in the meta-analysis did not [4]; a systematic review speaks of “possibly effective” [5].

  • Testosterone ↑ at a low baseline value

    Small benefit

    Testosterone & hormones · Patients: men with low testosterone or age-related hypogonadism · Human, randomised

    In the hypogonadal subgroup of the meta-analysis, a significant increase, but very heterogeneous (I² 89%) [4]. The largest RCT (n = 105) found an increase in total but not free testosterone compared with placebo and was funded by the manufacturer [7]; an open-label study without a control group likewise reported an increase [6].

  • Libido and erection ↑

    Single unconfirmed finding

    Libido & sexual function · healthy · Human, randomised manufacturer-fundedAccording to their funding or competing-interest statements, all studies behind this result were paid for, wholly or in part, by the maker of the product or compound, or list employees of the maker among their authors. Manufacturer-funded studies on average come out more favourably for the product.

    One RCT with 109 men aged 30 to 55 found better scores for erectile function and libido; two coauthors worked at the manufacturer of the extract [8]. No independent replications were found.

  • Fertility and sperm quality ↑

    Single unconfirmed finding

    Testosterone & hormones · Patients: men with idiopathic infertility · Human, non-randomised

    Only one open-label study without a control group; of 350 men, 75 were analyzed, and their sperm parameters improved [9]. Not studied in healthy men.

  • Less stress, cortisol ↓

    Single unconfirmed finding

    Mood & stress · healthy · Human, randomised small studiesEvery study behind this level and result had fewer than 100 participants. Small studies report larger effects on average than large ones, so the result is less certain.manufacturer-fundedAccording to their funding or competing-interest statements, all studies behind this result were paid for, wholly or in part, by the maker of the product or compound, or list employees of the maker among their authors. Manufacturer-funded studies on average come out more favourably for the product.

    A manufacturer-funded RCT with 63 moderately stressed adults found less tension and 16% lower salivary cortisol after four weeks [10].

small studies: Every study behind this level and result had fewer than 100 participants. Small studies report larger effects on average than large ones, so the result is less certain.

manufacturer-funded: According to their funding or competing-interest statements, all studies behind this result were paid for, wholly or in part, by the maker of the product or compound, or list employees of the maker among their authors. Manufacturer-funded studies on average come out more favourably for the product.

Mechanism of action

Evidence map: Tongkat Ali

Each line stands for a published finding; line style and color show where it comes from. The filter hides weaker evidence levels. Sources: see references.

The best-known constituent is the quassinoid eurycomanone. In isolated rat testicular cells rich in Leydig cells, it increased testosterone formation in a concentration-dependent manner (0.1 to 10 µM); the authors explain this mainly by inhibition of aromatase, which converts testosterone into estradiol, and at high concentration additionally by inhibition of phosphodiesterases. Binding to aromatase was shown only in a computer model (docking) [1]. Eurycomanone is poorly absorbed: the oral bioavailability of the pure compound was 11.8% in rats and 54.9% in mice, and the half-life was 0.3 hours; such data are lacking in humans [2].

Whether this mechanism plays a role in humans is unresolved. In a placebo-controlled study with 32 young, healthy men, total and free testosterone rose after two weeks, but so did estradiol, while LH, FSH, and SHBG remained unchanged; this fits neither aromatase inhibition nor activation of the hypothalamic-pituitary-gonadal axis [3]. A meta-analysis of five RCTs found an overall increase in total testosterone (standardized mean difference 1.35), albeit with very high heterogeneity (I² 87%); in the subgroup of men with normal testosterone, the effect was not significant, whereas in men with low testosterone it was [4]. A systematic review rates tongkat ali as “possibly effective” for men with age-related hypogonadism and for healthy men [5].

The studies in men with low testosterone are in part uncontrolled [6] and in part funded by the manufacturer of the extract tested [7]. Manufacturer employees were also involved in the RCT on quality of life and erectile function [8]. The study on sperm quality in infertile men was open-label and without a control group, and only 75 of 350 participants were analyzed [9]; the study on stress hormones was in turn funded by the manufacturer [10]. On safety: EFSA found indications of genotoxicity in the laboratory and in animal experiments [11], there is a case report [12] and there are reports of liver injury in bodybuilders [13]. Examinations of commercial products found mercury above the Malaysian limit in 26 of 100 products [14] and indications of a sildenafil analogue in two products bought online [15].

Targets

TargetTypeActionKey dataEvidence
Aromatase (CYP19A1)EnzymeInhibitoronly indirect (cell culture) and by docking; no IC50 published Laboratory[1]
Phosphodiesterases in Leydig cellsEnzymeInhibitorsuspected only at high concentration (rat Leydig cells) Laboratory[1]
Testosterone synthesis in Leydig cellsSignaling pathwayActivatorIncrease at 0.1–10 µM eurycomanone (rat, in vitro) Laboratory[1]

Effect profile

Which signaling systems the compound affects according to current data. ↑ enhanced, ↓ dampened, ≈ modulated, ○ no effect; dots = evidence level.

  • Dopamineno data
  • Noradrenalineno data
  • Serotoninno data
  • Acetylcholineno data
  • Glutamate · AMPAno data
  • Glutamate · NMDAno data
  • GABAno data
  • Histamineno data
  • Orexinno data
  • Adenosineno data
  • Opioidsno data
  • Melatoninno data
  • Neurotrophinsno data
  • Blood flowno data
  • Nitric oxideno data
  • Energy metabolismno data
  • Insulin · glucoseno data
  • Inflammation · oxidativeno data
  • Stress axis↓ · Salivary cortisol 16% lower in a manufacturer-funded RCT in stressed adults[10]
  • Testosterone axis↑ · Total testosterone raised in RCTs mainly at a low baseline value; LH and FSH unchanged in young men, estradiol increased[3][4][7]
  • Endocannabinoidsno data
  • Autophagy · senescenceno data
  • Immune systemno data
  • Lipid metabolismno data
  • Coagulation · fibrinolysisno data
  • Methylationno data

Routes of administration and bioavailability

How much of a compound reaches the blood or target tissue depends on the route into the body and on the dosage form. All routes of administration explained

  • Oral (swallowed) · Water extract of the root, standardized (e.g., to eurycomanone)

    Eurycomanone: 11.8% (rat), 54.9% (mouse); human unknown

    Eurycomanone crosses biological membranes poorly but is metabolically stable after absorption; the half-life in rodents was 0.3 hours, both as the pure compound and in the extract [2]. Most clinical studies used the same commercial water extract [4]; results therefore cannot readily be transferred to other products.

    Animal study

Human studies

  • Meta-analysis, total testosterone

    systematic review (9 studies) with meta-analysis of 5 RCTs · healthy and hypogonadal men · n = 232 · varied

    Measured: Total testosterone in serum

    Result: SMD 1.35 (95% CI 0.57–2.14), I² 87%; subgroup normal testosterone not significant, subgroup hypogonadism significant.[4]

    Human, randomised

  • Systematic review of “testosterone boosters”

    systematic review (52 studies, 27 substances) · Athletes, age-related hypogonadism, infertile and healthy men · varied

    Measured: Total testosterone vs. placebo

    Result: Eurycoma longifolia “possibly effective” in age-related hypogonadism and in healthy men (3 studies).[5]

    Human, randomised

  • Young healthy men

    RCT, double-blind, placebo-controlled, pair-matched · healthy (men, mean age 24 years) · n = 32 · 2 weeks

    Measured: Testosterone, free testosterone, estradiol, LH, FSH, SHBG

    Result: Testosterone, free testosterone, and estradiol rose; LH, FSH, SHBG unchanged.[3]

    Human, randomised

  • Older men with low testosterone

    RCT, double-blind, placebo-controlled, multicenter; funded by the manufacturer · Patients: men aged 50–70 years with testosterone < 300 ng/dl · n = 105 · 12 weeks

    Measured: Total and free testosterone

    Result: Total testosterone raised compared with placebo; free testosterone without a difference between the groups.[7]

    Human, randomised

  • Age-related hypogonadism

    open-label, without a control group · Patients: men with age-related hypogonadism · n = 76 · 1 month

    Measured: AMS score, testosterone

    Result: AMS score and testosterone improved; proportion with normal testosterone from 35.5% to 90.8%.[6]

    Human, non-randomised

  • Quality of life and sexual function

    RCT, double-blind, placebo-controlled; coauthors at the manufacturer · healthy (men aged 30–55 years) · n = 109 · 12 weeks

    Measured: SF-36, IIEF

    Result: Physical functioning, erectile function, and libido better than with placebo.[8]

    Human, randomised

  • Idiopathic infertility

    open-label, without a control group · Patients: men from subfertile couples · n = 75 · 3–9 months

    Measured: Sperm parameters

    Result: All sperm parameters improved; only 75 of 350 participants analyzed.[9]

    Human, non-randomised

  • Stress hormones and mood

    RCT, placebo-controlled; funded by the manufacturer · healthy (moderately stressed women and men) · n = 63 · 4 weeks

    Measured: Salivary cortisol and testosterone, mood profile

    Result: Tension −11%, anger −12%, cortisol −16%, testosterone +37%.[10]

    Human, randomised

Risks and warnings

  • Indications of genotoxicity

    A standardized water extract was positive in the chromosomal aberration test and, in the comet assay in rodents, damaged DNA in the stomach and duodenum at the highest dose; EFSA therefore considered safety not established under any condition of use [11].

    Animal study

  • Liver injury

    A case report describes acute liver injury with jaundice in a 47-year-old man that resolved after discontinuation [12]; LiverTox mentions reports of liver injury in bodybuilders [13].

    Human, non-randomised

  • Heavy metals

    In 26 of 100 products from Malaysia, the mercury content was above the national limit [14].

    Laboratory

  • Adulteration with pharmaceutical compounds

    Two of ten products examined, both bought online, showed spectroscopic indications of a sildenafil analogue [15].

    Laboratory

  • Manufacturer-funded evidence base

    Seven of nine studies in the systematic review tested the same commercial extract [4]; several RCTs were funded by the manufacturer or conducted with its employees [7][8][10].

    No data

Fact check: common claims

  • not supported

    “Tongkat ali markedly increases testosterone in every man”

    In men with normal testosterone, the pooled effect was not significant [4]; the increase is more robust only at a low baseline value, and even there the studies are small and heterogeneous [4][7].

  • not supported

    “Tongkat ali is a natural aromatase inhibitor and lowers estrogen”

    The aromatase inhibition comes from rat Leydig cells and docking [1]; in young men, estradiol even rose under tongkat ali [3].

  • partly supported

    “Tongkat ali lowers cortisol”

    Lower salivary cortisol in one RCT [10] and a decline within the group in another [7]; both funded by the manufacturer.

  • refuted

    “Because it is a natural product, tongkat ali is harmless”

    EFSA considered safety not established because of indications of genotoxicity [11]; in addition there are a case report on liver injury [12] and findings of mercury [14] and a sildenafil analogue [15] in commercial products.

Pharmacokinetics

Absorption
Eurycomanone is poorly absorbed across biological membranes (Caco-2 cells, PAMPA) [2].
Half-life
0.3 hours in rats and mice; not studied in humans [2].
Metabolism
Stable in liver microsomes of several species including human, hardly any breakdown [2].
Entry into the brain
Not studied.

Legal status

Germany
Not verified; the novel food status in the EU is decisive [11].
EU
In 2021, EFSA assessed a standardized water extract of the root as a novel food and concluded that its safety has not been established under any condition of use (indications of genotoxicity) [11]. Whether an authorization followed was not checked.
USA
Widely available as an herbal product and listed in the NIH LiverTox database [13]; legal status not verified.
Other countries
Malaysia: traditional medicine subject to registration with the drug regulatory authority (DCA) [14].

Related compounds

Fadogia agrestissame class (German only)Tribulus terrestrissame class (German only)Macasame class (German only)Icariin (Epimedium, „Horny Goat Weed“)same class (German only)

Open questions

  • Does testosterone rise in men with a normal baseline value in large, manufacturer-independent RCTs?
  • Through which mechanism does testosterone rise in humans when LH remains unchanged and estradiol rises?
  • Are the genotoxic findings from the EFSA assessment relevant to humans for the usual extracts?
  • How well is eurycomanone absorbed in humans?

References

  1. Low BS, Choi SB, Abdul Wahab H, Das PK, Chan KL. Eurycomanone, the major quassinoid in Eurycoma longifolia root extract increases spermatogenesis by inhibiting the activity of phosphodiesterase and aromatase in steroidogenesis. J Ethnopharmacol. 2013;149(1):201–7. doi:10.1016/j.jep.2013.06.023 · PubMed
  2. Ahmad N, Samiulla DS, Teh BP, Zainol M, Zolkifli NA, Muhammad A, et al. Bioavailability of eurycomanone in its pure form and in a standardised Eurycoma longifolia water extract. Pharmaceutics. 2018;10(3):90. doi:10.3390/pharmaceutics10030090 · PubMed
  3. Chan KQ, Stewart C, Chester N, Hamzah SH, Yusof A. The effect of Eurycoma longifolia on the regulation of reproductive hormones in young males. Andrologia. 2021;53(4):e14001. doi:10.1111/and.14001 · PubMed
  4. Leisegang K, Finelli R, Sikka SC, Panner Selvam MK. Eurycoma longifolia (Jack) improves serum total testosterone in men: a systematic review and meta-analysis of clinical trials. Medicina (Kaunas). 2022;58(8):1047. doi:10.3390/medicina58081047 · PubMed
  5. Morgado A, Tsampoukas G, Sokolakis I, Schoentgen N, Urkmez A, Sarikaya S. Do “testosterone boosters” really increase serum total testosterone? A systematic review. Int J Impot Res. 2024;36(4):348–64. doi:10.1038/s41443-023-00763-9 · PubMed
  6. Tambi MI, Imran MK, Henkel RR. Standardised water-soluble extract of Eurycoma longifolia, Tongkat ali, as testosterone booster for managing men with late-onset hypogonadism? Andrologia. 2012;44 Suppl 1:226–30. doi:10.1111/j.1439-0272.2011.01168.x · PubMed
  7. Chinnappan SM, George A, Pandey P, Narke G, Choudhary YK. Effect of Eurycoma longifolia standardised aqueous root extract-Physta® on testosterone levels and quality of life in ageing male subjects: a randomised, double-blind, placebo-controlled multicentre study. Food Nutr Res. 2021;65:5647. doi:10.29219/fnr.v65.5647 · PubMed
  8. Ismail SB, Wan Mohammad WM, George A, Nik Hussain NH, Musthapa Kamal ZM, Liske E. Randomized clinical trial on the use of PHYSTA freeze-dried water extract of Eurycoma longifolia for the improvement of quality of life and sexual well-being in men. Evid Based Complement Alternat Med. 2012;2012:429268. doi:10.1155/2012/429268 · PubMed
  9. Tambi MI, Imran MK. Eurycoma longifolia Jack in managing idiopathic male infertility. Asian J Androl. 2010;12(3):376–80. doi:10.1038/aja.2010.7 · PubMed
  10. Talbott SM, Talbott JA, George A, Pugh M. Effect of Tongkat Ali on stress hormones and psychological mood state in moderately stressed subjects. J Int Soc Sports Nutr. 2013;10(1):28. doi:10.1186/1550-2783-10-28 · PubMed
  11. EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA); Turck D, Bohn T, Castenmiller J, De Henauw S, Hirsch-Ernst KI, Maciuk A, et al. Safety of Eurycoma longifolia (Tongkat Ali) root extract as a novel food pursuant to Regulation (EU) 2015/2283. EFSA J. 2021;19(12):e06937. doi:10.2903/j.efsa.2021.6937 · PubMed
  12. Kaliounji A, Shadid G, Saba H, Ahlawat S. A rare case of Tongkat Ali-induced liver injury: a case report. Cureus. 2024;16(3):e56639. doi:10.7759/cureus.56639 · PubMed
  13. Tongkat Ali. In: LiverTox: clinical and research information on drug-induced liver injury [Internet]. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases; 2012– [aktualisiert 18.10.2024]. PubMed
  14. Ang HH, Lee KL. Contamination of mercury in tongkat Ali hitam herbal preparations. Food Chem Toxicol. 2006;44(8):1245–50. doi:10.1016/j.fct.2006.01.014 · PubMed
  15. Said MM, Gibbons S, Moffat AC, Zloh M. Rapid detection of sildenafil analogue in Eurycoma longifolia products using a new two-tier procedure of the near infrared (NIR) spectra database. Food Chem. 2014;158:296–301. doi:10.1016/j.foodchem.2014.02.125 · PubMed
How this profile was checked

Last reviewed: 2026-10-23. All sources with a DOI or PMID were resolved automatically via Crossref or doi.org and PubMed.

Translated from the German profile (version of 2026-10-23); translation checked on 2026-10-26.

Checked

  • All DOIs via Crossref, PMIDs via PubMed with a checking script; [13] without a DOI, via PMID only.
  • From the abstracts: 0.1–10 µM, aromatase/PDE, docking [1]; 11.8% rat, 54.9% mouse, t½ 0.3 h, microsomes stable [2]; n = 32, 2 weeks, T/fT/E2 ↑, LH/FSH/SHBG unchanged [3]; 52 studies, “possibly effective” [5]; n = 76, 35.5% → 90.8% [6]; n = 105, free T without a group difference [7]; n = 109, IIEF, libido [8]; 350 participants, 75 analyzed [9]; n = 63, −11/−12/−16%, +37% [10]; genotoxicity, “safety … not established under any condition of use” [11]; case report age 47 [12]; bodybuilders [13]; 26 of 100, limit 0.5 ppm [14]; 2 of 10 products [15].
  • In the full text of [4]: 5 RCTs, n = 232, SMD 1.352, I² 87.27%; subgroup normal testosterone SMD 0.76 (95% CI −0.54 to 2.06; p = 0.249; 88 participants); subgroup hypogonadism SMD 1.86 (0.72–3.00), I² 89%; 7 of 9 studies with Physta; no conflicts of interest, no external funding.
  • Conflicts of interest in the full text: [7] funded by the manufacturer Biotropics, two authors employed there; [8] two authors with a Biotropics affiliation; [10] funded by Biotropics.
  • ClinicalTrials.gov: 5 entries for Eurycoma longifolia (October 23, 2026).
  • October 26, 2026, precision flags (m004; rules in the guideline under “Number rule and precision flags,” implementation by Claude pending confirmation by Tilman): “Libido and erection ↑”: “herstellerfinanziert” – [8] two authors with an affiliation at the manufacturer Biotropics (full text, see above). “Less stress, cortisol ↓”: “kleine_studien”, “herstellerfinanziert” – [10] 63 adults (abstract); according to the full text funded by Biotropics (see above).

Not verified

  • Whether an EU authorization as a novel food was granted or refused after the negative EFSA opinion; status in Germany and the USA.
  • Conflicts of interest of studies [6] and [9] (only abstract read).
  • The number of pregnancies in [9] (truncated in the abstract) was not adopted.

No dosages, no sources of supply. This information does not replace medical advice.

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