The two ashwagandha extracts with the strongest clinical evidence for raising testosterone are KSM-66 and Shoden. Both have produced statistically significant increases of roughly 15–17% in placebo-controlled trials, though they work at very different doses because their concentrations of active compounds differ dramatically. Choosing between them comes down to understanding what’s in each extract and what the research actually tested.
The Three Main Extracts, Compared
Not all ashwagandha supplements are the same product. The plant’s active compounds, called withanolides, are what drive its hormonal effects, and the three major branded extracts concentrate them to very different degrees:
- KSM-66 contains 5% withanolides, extracted from the root only using a water-based process.
- Sensoril contains 10% withanolides, extracted from both root and leaf.
- Shoden contains 35% withanolides, also extracted from root and leaf using an ethanol-water process.
A higher withanolide percentage doesn’t automatically mean “better.” It means you need a smaller pill to deliver the same amount of active compound. A 600 mg dose of KSM-66 delivers about 30 mg of withanolides. A 600 mg dose of Shoden delivers roughly 210 mg. These are fundamentally different doses of active ingredient, so comparing them milligram-for-milligram makes no sense. What matters is whether each extract, at its studied dose, actually moved the needle on testosterone in a controlled trial.
What the Testosterone Trials Found
A systematic review published in Advances in Nutrition pulled together the clinical data on ashwagandha and testosterone in men. Four relevant studies used either KSM-66 or Shoden, and three of the four showed significant testosterone increases.
KSM-66 was tested in two populations. In 57 young men (average age 28), 600 mg daily for 8 weeks raised testosterone by 15.3% compared to placebo. In 46 infertile men (average age around 34), a slightly higher dose of 675 mg daily for 90 days raised testosterone by 17.3%.
Shoden was also tested in two populations. In 57 overweight men aged 40–70 with mild fatigue, 600 mg daily (delivering 21 mg of withanolide glycosides) for 8 weeks raised testosterone by 14.7% and the testosterone precursor DHEA-S by 18%. However, a second Shoden study using a lower dose of 240 mg daily in stressed but otherwise healthy men found no significant change in testosterone after 60 days.
The takeaway: both KSM-66 and Shoden raised testosterone by a similar percentage when dosed correctly. Neither extract clearly outperforms the other based on available trials. The one study that failed used a lower dose of Shoden, suggesting that dose matters more than brand.
Why Dose Matters More Than Brand
The failed Shoden study used 240 mg daily. The successful one used 600 mg. That’s less than half the effective dose, and the testosterone response disappeared. The same pattern holds across the KSM-66 trials, where effective doses were 600–675 mg daily.
If you pick a supplement based on brand name but take it below the studied dose, you’re unlikely to see the results those studies reported. When shopping, check the supplement facts panel for two things: which extract is used and how many milligrams per serving. For KSM-66, look for 600 mg daily. For Shoden, the effective dose in the testosterone trial was also 600 mg daily.
How Ashwagandha Affects Hormones
Ashwagandha appears to influence testosterone through the brain’s stress-hormone system. The active compounds interact with calming receptors in the hypothalamus, which triggers a signaling cascade: the brain releases more of the hormones (LH and FSH) that tell the testes to produce testosterone. At the same time, ashwagandha lowers cortisol, the body’s primary stress hormone. Since chronically elevated cortisol suppresses testosterone production, reducing it may remove a brake on your natural hormone output.
This mechanism helps explain why the effects tend to be more pronounced in men who are stressed, fatigued, or overweight. If your cortisol is already low and your hormonal signaling is functioning well, there may be less room for ashwagandha to make a difference. The clinical trials consistently recruited men with some degree of stress, fatigue, or subfertility, not elite athletes with already-optimized hormone profiles.
What About Sensoril?
Sensoril, the third major extract at 10% withanolides, is widely studied for stress reduction and sleep quality but has not been tested in a placebo-controlled trial specifically measuring testosterone as a primary outcome. That doesn’t mean it can’t affect testosterone (its cortisol-lowering effects could theoretically help), but there isn’t direct clinical evidence to recommend it for that purpose. If testosterone is your specific goal, KSM-66 and Shoden have the data behind them.
How Long Until You See Results
The clinical trials measured testosterone at the 8-week mark, and that’s where statistically significant changes showed up. The KSM-66 infertility study ran for 90 days (about 13 weeks) and found slightly larger increases, which may reflect continued improvement over a longer supplementation window. Plan on at least two months of consistent daily use before expecting measurable hormonal changes. This isn’t something that shifts in a few days.
Strength and Body Composition Effects
Beyond the hormone numbers, ashwagandha supplementation has been linked to measurable improvements in physical performance. In a randomized controlled trial of young men doing resistance training, those taking ashwagandha saw significantly greater increases in bench press strength (46 kg improvement vs. 26.4 kg in the placebo group) over 8 weeks. The ashwagandha group also had greater increases in muscle size in both the arms and thighs. Whether these gains were driven directly by the testosterone increase or by other recovery-related effects of ashwagandha isn’t fully clear, but the combination of hormonal and performance benefits is what makes it popular among men who exercise.
Safety Considerations
Ashwagandha is generally well tolerated at the doses used in clinical trials (600–675 mg daily for 8–13 weeks). However, cases of liver injury have been reported in people taking ashwagandha, particularly at high doses. One documented case involved a woman taking 2,100 mg daily for a year who developed jaundice and significant liver inflammation, which resolved after stopping the supplement. She was also taking ibuprofen regularly and drinking alcohol, making it hard to pin the damage on ashwagandha alone, but the pattern has appeared in enough case reports to warrant caution. Sticking to studied doses and avoiding indefinite, uninterrupted use is a reasonable approach.
Practical Buying Guide
When choosing an ashwagandha supplement specifically for testosterone support, here’s what to prioritize:
- Extract type: Look for KSM-66 or Shoden on the label. Generic “ashwagandha root powder” hasn’t been tested in the same way and delivers far fewer active compounds per capsule.
- Daily dose: 600 mg for either KSM-66 or Shoden. Some products split this across two capsules taken together or separately.
- Withanolide content: KSM-66 should list 5% withanolides, Shoden should list 35% withanolide glycosides. If these numbers aren’t on the label, the manufacturer may not be using the genuine branded extract.
- Timing: The Shoden testosterone trial had participants take their dose about 2 hours after food, preferably after dinner. KSM-66 studies typically used dosing with meals. Either approach is fine as long as you’re consistent.
Both extracts produce similar testosterone increases in the range of 15–17% over 8 weeks. KSM-66 is more widely available and tends to be cheaper. Shoden delivers more withanolides per milligram, which means smaller pills but often a higher price per bottle. For most people, the practical difference between the two is cost and availability rather than effectiveness.