You'll find both herbs in most men's testosterone formulas, yet the evidence for each leans a different way. We look at what each was tested for, at which doses, and what the safety trade-offs are.
Ashwagandha has the larger body of evidence for stress and sleep: several small trials show lower stress scores and cortisol. Tongkat ali makes a slightly more direct case for testosterone, mainly in men who start out low. Both herbs rest on small studies, and neither takes the place of testing or treatment for true low testosterone.
Ashwagandha is chiefly a stress and sleep herb that also has some testosterone data. Tongkat ali is studied mainly for testosterone, plus one small trial on stress hormones. If stress, poor sleep and fatigue are what bother you most, ashwagandha has more behind it. Borderline-low testosterone on a blood test favors tongkat ali, which offers a more targeted evidence base, though a thin one.
| Ashwagandha | Tongkat ali | |
|---|---|---|
| Plant part | Root, sometimes with leaf, of Withania somnifera | Root of the plant Eurycoma longifolia |
| Strongest evidence | Stress, sleep and cortisol | Testosterone in men with low levels |
| Testosterone evidence | Some small trials, mostly of men who exercise or who are older and overweight | Meta-analysis covering 5 small RCTs (232 men) |
| Doses studied | Extract at about 240 to 1,250 mg/day, with 300 to 600 mg common | Water extract at 100 to 600 mg/day, with 200 to 400 mg common |
| Main safety concerns | Rare liver injury and thyroid effects; avoid in pregnancy | Long-term data is limited, extract quality varies, and there are cautions with hormone-related drugs |
In 2015, the Journal of the International Society of Sports Nutrition published what is probably the best-known ashwagandha testosterone trial. It enrolled 57 men starting a resistance training program, and they took KSM-66 root extract (600 mg a day) or placebo for eight weeks. Testosterone rose by about 96 ng/dL with ashwagandha, against 18 ng/dL with placebo, and strength gains were larger. The manufacturer supplied the extract. At the end, testosterone levels did not differ significantly between the groups.
A different extract (Shoden) featured in a 2019 crossover trial in the American Journal of Men's Health, with 57 overweight men aged 40 to 70 who had mild fatigue. Salivary testosterone rose 14.7% more than with placebo, and DHEA-S 18% more. Fatigue, vigor and sexual well-being did not improve more than placebo, though, a handy reminder that a lab number can move without you feeling any different.
NCCIH's summary is limited evidence that two to four months of ashwagandha may increase testosterone and sperm quality (NCCIH). Trials of specific brands get their own treatment in our KSM-66 ashwagandha guide.
A 2022 meta-analysis in Medicina covers tongkat ali. It pooled five randomized trials (232 men) at 100 to 600 mg a day, mostly of a single standardized water extract, and total testosterone rose significantly overall. The rise was significant in men starting below 300 ng/dL but not in men with normal levels. The authors flagged high variation between studies and signs of publication bias.
The largest single trial enrolled 105 men aged 50 to 70 with low testosterone. Over 12 weeks, 100 to 200 mg a day raised total testosterone versus placebo. Two authors were employed by the extract's manufacturer. For study-by-study detail, see our complete guide to tongkat ali and testosterone.
Men with confirmed low or borderline-low levels get a slight edge from tongkat ali, since its trials went after that group directly. Most of ashwagandha's testosterone results come from men who were training or already in normal ranges. In both cases, expect a modest change at best, nothing like the jump prescription therapy can bring.
Here ashwagandha is clearly ahead. The NIH Office of Dietary Supplements points to a 2021 systematic review that covered seven trials and 491 adults. At 240 to 1,250 mg a day over six to eight weeks, ashwagandha lowered stress, anxiety, sleeplessness, fatigue and serum cortisol. Sleep is a separate matter: a 2021 meta-analysis of five studies (372 adults) reported a small but significant benefit, larger at 600 mg a day and in people with insomnia.
Gaps remain. Most trials are small, short and use different preparations, the ODS notes, and a 12-week trial of 400 mg a day failed to reduce perceived stress. For the mixed results, read our review of whether ashwagandha works.
Tongkat ali's stress evidence is a single four-week trial in the Journal of the International Society of Sports Nutrition, in which 63 moderately stressed adults took 200 mg a day. Against placebo, cortisol was 16% lower and testosterone 37% higher, with modest mood improvements. The extract's maker funded it, and it hasn't been widely replicated.
Both the ODS and NCCIH call ashwagandha well tolerated in general for up to about three months, and long-term safety is unknown. Points worth knowing:
Side effects were few in trials lasting up to a few months, although one noted stomach upset and itching. There's no long-term data. Because the aim is to raise testosterone, ask your doctor first if you use prescription testosterone or antiandrogen drugs for prostate cancer, or have a prostate condition. Product quality poses the bigger real-world risk. The meta-analysis cites testing where under half of products reached the expected level of the active marker compound.
Plenty of men's formulas combine the two, and no direct interaction between them is known. Still, the combination has no good trials, so any claim that they "stack" into a bigger effect is a guess.
To try both, add them one at a time and give each six to eight weeks, so you can tell what's doing what. Make sure any combined product lists studied doses rather than a small sprinkle of each. Testosterone is the goal for many men, in which case a morning testosterone test before and after is worthwhile. Both herbs carry cautions, so talk to your doctor first if you take thyroid, diabetes, blood pressure or hormone-related medicines, or have a prostate condition.
These two herbs can't be swapped for each other. Ashwagandha makes the stronger case for stress, sleep and cortisol, and some trials show a small testosterone effect. Tongkat ali has the more focused testosterone data, chiefly in men who start low. Small studies, often run with the extract makers, support both. So keep expectations modest, choose a standardized extract at a studied dose, and use a blood test, not marketing claims, to judge whether it's working.