Both herbs show up in most men's testosterone formulas, but their evidence points in different directions. Here's what each has been tested for, at what doses, and the safety trade-offs.
For stress and sleep, ashwagandha has the larger body of evidence, with multiple small trials showing lower stress scores and cortisol. For testosterone, tongkat ali has a slightly more direct case, mainly in men with low starting levels, though both herbs rest on small studies. Neither replaces testing or treatment for true low testosterone.
Ashwagandha is mainly a stress and sleep herb with some testosterone data on the side. Tongkat ali is mainly studied as a testosterone herb, with one small trial on stress hormones. If stress, poor sleep and fatigue are your main complaints, ashwagandha has more to go on. If a blood test shows borderline-low testosterone, tongkat ali has a more targeted, if still thin, evidence base.
| Ashwagandha | Tongkat ali | |
|---|---|---|
| Plant part | Root (sometimes root and leaf) of Withania somnifera | Root of Eurycoma longifolia |
| Strongest evidence | Stress, sleep, cortisol | Testosterone in men with low levels |
| Testosterone evidence | A few small trials, mostly in men who exercise or are older and overweight | Meta-analysis of 5 small RCTs (232 men) |
| Doses studied | About 240 to 1,250 mg/day of extract; 300 to 600 mg common | 100 to 600 mg/day of water extract; 200 to 400 mg common |
| Main safety flags | Rare liver injury, thyroid effects, avoid in pregnancy | Limited long-term data, extract quality varies, hormone-related drug cautions |
The most cited ashwagandha testosterone study is a 2015 trial in the Journal of the International Society of Sports Nutrition. Fifty-seven men starting a resistance training program took 600 mg a day of KSM-66 root extract or placebo for eight weeks. Testosterone rose by about 96 ng/dL in the ashwagandha group versus 18 ng/dL with placebo, and strength gains were larger. The extract was supplied by its manufacturer, and final testosterone levels weren't significantly different between groups.
A 2019 crossover trial in the American Journal of Men's Health gave a different extract (Shoden) to 57 overweight men aged 40 to 70 with mild fatigue. Salivary testosterone rose 14.7% more than with placebo, and DHEA-S 18% more. But fatigue, vigor and sexual well-being didn't improve more than placebo, which is a useful reality check: a lab number moving doesn't always mean you feel different.
The NCCIH sums it up as limited evidence that taking ashwagandha for two to four months may increase testosterone and sperm quality. We cover the brand-specific trials in our KSM-66 ashwagandha guide.
A 2022 meta-analysis in Medicina pooled five randomized trials (232 men) using 100 to 600 mg a day, mostly of one standardized water extract. Tongkat ali significantly raised total testosterone overall. The rise was significant in men starting below 300 ng/dL, but not in men with normal levels. The authors also flagged high variation between studies and signs of publication bias.
The largest single trial, in 105 men aged 50 to 70 with low testosterone, found 100 to 200 mg a day raised total testosterone versus placebo over 12 weeks. Two authors worked for the extract's manufacturer. Our full tongkat ali testosterone guide goes through each study in more detail.
Tongkat ali edges it for men with confirmed low or borderline-low levels, because its trials targeted that group directly. Ashwagandha's testosterone results come mostly from men who were training or already in normal ranges. Either way, expect a modest change at best, not the jump you'd see with prescription therapy.
This is where ashwagandha clearly leads. According to the NIH Office of Dietary Supplements, a 2021 systematic review of seven trials in 491 adults found ashwagandha reduced stress, anxiety, sleeplessness, fatigue and serum cortisol over six to eight weeks, at 240 to 1,250 mg a day. A 2021 meta-analysis of five studies (372 adults) found a small but significant benefit for sleep, larger at 600 mg a day and in people with insomnia.
The evidence isn't spotless. The ODS notes most trials are small, short and use different preparations, and one 12-week trial of 400 mg a day didn't reduce perceived stress. Our review of whether ashwagandha works covers the mixed results.
Tongkat ali's stress data is one four-week trial of 63 moderately stressed adults taking 200 mg a day, published in the Journal of the International Society of Sports Nutrition. Cortisol was 16% lower and testosterone 37% higher than placebo, with modest mood improvements. It was funded by the extract's maker and hasn't been widely replicated.
The ODS and NCCIH describe ashwagandha as generally well tolerated for up to about three months, with long-term safety unknown. Points to know:
Trials of up to a few months reported few side effects, though one noted stomach upset and itching. Long-term data is lacking. Because it's taken to raise testosterone, clear it with your doctor if you use prescription testosterone or antiandrogen drugs for prostate cancer, or have a prostate condition. The bigger practical risk is product quality: the meta-analysis cites testing where fewer than half of products met the expected level of the active marker compound.
Many men's formulas combine them, and there's no known direct interaction between the two. But there are no good trials of the combination either, so any claim that they "stack" for a bigger effect is a guess.
If you want to try both, a sensible approach is to start one at a time for six to eight weeks so you can tell what's doing what, and to check that a combined product actually lists studied doses rather than a small sprinkle of each. Get a morning testosterone test before and after if testosterone is the goal. And if you take thyroid, diabetes, blood pressure or hormone-related medicines, or have a prostate condition, talk to your doctor first, since both herbs carry cautions there.
Ashwagandha and tongkat ali aren't interchangeable. Ashwagandha has the stronger case for stress, sleep and cortisol, with a small testosterone effect in some trials. Tongkat ali has the more focused testosterone data, mainly in men with low starting levels. Both rest on small studies, often run with the extract manufacturers, so keep expectations modest, pick a standardized extract at a studied dose, and use a blood test rather than marketing claims to judge whether it's working.