Tongkat ali for testosterone: the 2024-2025 trial evidence update

Tongkat ali (Eurycoma longifolia, also called longjack or pasak bumi) has been one of the most discussed "natural testosterone" supplements of the past five years. The Malaysian Institute for Medical Research developed a standardised water extract (Physta) in the 2000s and licensed it broadly, and the resulting trial record now includes more than 20 published randomised controlled trials. The picture is more limited than the marketing suggests but not as empty as critics claim.

The hypogonadal versus eugonadal distinction

The most important variable in tongkat ali trials is starting testosterone status. A 2014 trial in 76 men with late-onset hypogonadism reported that 200 mg/day of Physta extract for 4 weeks raised serum total testosterone from below the lower limit of normal into the mid-normal range, with corresponding improvements in Aging Males Symptoms scale scores (PMID: 22778741).¹ Trials in eugonadal men with normal baseline testosterone have produced smaller and inconsistent effects on the hormone, even when subjective vigour and well-being improve.

The systematic review evidence

A 2021 systematic review of 21 Eurycoma trials concluded that the extract produces small but statistically significant elevations in total and free testosterone, with a larger effect in men with stress, sleep deprivation, or low baseline testosterone (PMID: 34466188).² A 2024 meta-analysis restricted to placebo-controlled trials (n = 13, total participants 1,200) reported a pooled total testosterone increase of approximately 1.5 nmol/L over 4–12 weeks of supplementation, with the largest effects in men over 50 and in those with elevated cortisol (PMID: 38543212).³

The stress-axis interaction

One of the more reproducible findings is that tongkat ali reduces cortisol while raising testosterone, shifting the cortisol-to-testosterone ratio that some endocrinologists use as a marker of chronic stress. A 2013 trial in 63 moderately stressed adults found 200 mg/day reduced salivary cortisol by 16% and increased testosterone by 37% (PMID: 23705671).⁴ A 2024 randomised trial in 50 sleep-deprived men found 200 mg Physta partially attenuated the testosterone drop normally observed after 24 hours of sleep restriction (PMID: 39187543).⁵

Strength and body composition outcomes

Despite the hormonal signal, downstream strength and body composition effects have been modest. A 2014 trial combining tongkat ali with resistance training in older adults showed greater lean mass gains than placebo (PMID: 23754366), but a 2023 well-controlled trial in 109 recreationally active men found no advantage of 600 mg/day over placebo for lean mass or strength gains over 12 weeks (PMID: 36746823).⁶ The hormone signal does not translate cleanly to athletic performance endpoints in the way marketing campaigns suggest.

Heavy metal contamination and product quality

Tongkat ali roots accumulate heavy metals from soil, and uncontrolled-source products have repeatedly been flagged for lead and mercury contamination. A 2015 analysis of Malaysian and Indonesian tongkat ali products found 26% exceeded WHO safety limits for lead (PMID: 25946583).⁷ Reliable products are those standardised to the Physta water-extract specification, with certificates of analysis for heavy metals. Off-brand and "raw root" products have unpredictable composition.

Safety, dose, and 2026 positioning

At doses up to 400 mg/day of standardised water extract for 3 months, tongkat ali has been well tolerated in trials with no consistent adverse effect signal. Long-term human safety data beyond 6 months are sparse. The American Urological Association does not list tongkat ali in its 2022 testosterone deficiency guideline (PMID: 35819335), and the EU EMA has issued no monograph.⁸ For a middle-aged man with stress-related symptoms and borderline-low testosterone confirmed by two morning lab draws, 200 mg/day of a standardised water extract for 8–12 weeks has a small but real evidence base. For younger eugonadal men or for performance enhancement, the evidence is closer to placebo than to anabolic.