Supplement Published April 17, 2026

Ashwagandha for Testosterone: What the Studies Actually Show

Ashwagandha might be the most-hyped herbal supplement for testosterone right now. The evidence? More modest than the marketing. But it's not nothing. Here's what the studies actually show, what to look for, and whether it's worth taking.

What Is Ashwagandha?

Ashwagandha (Withania somnifera) is an adaptogenic herb used in Ayurvedic medicine for thousands of years. In the last decade it's exploded in popularity in the West, mostly because a handful of clinical trials suggest it modestly raises testosterone, reduces cortisol, and improves sleep and strength in certain populations.

The active compounds are called withanolides. Most clinical research uses one of two standardized extracts: KSM-66 (root-only, 5% withanolides) or Sensoril (root and leaf, 10% withanolides). KSM-66 has the most T-specific research behind it.

The Testosterone Studies

Wankhede et al. (2015)

57 men doing resistance training for 8 weeks. Half took 600 mg/day of KSM-66 ashwagandha. The ashwagandha group showed a testosterone increase of roughly 15% vs placebo, plus significantly more strength gains (bench press and leg extension) and muscle size.

Lopresti et al. (2019)

60 overweight, mildly-stressed men aged 40 to 70. Half took 600 mg/day of a different ashwagandha extract for 16 weeks. The ashwagandha group saw an 18% increase in testosterone and significant drops in DHEA-S and cortisol compared to placebo. This study focused on aging men with moderate stress, not athletes.

Ambiye et al. (2013)

46 infertile men with low sperm count. Ashwagandha 675 mg/day for 90 days led to a 17% increase in testosterone and improvements in semen parameters. Note: these men had clinical issues at baseline, so the effect is on a population that had room to improve.

Smith et al. (2023)

A more recent meta-analysis aggregating several trials suggested ashwagandha raises testosterone on average by roughly 14%, with larger effects in stressed, sedentary, or infertile populations and smaller effects in young, already-healthy men.

How It Probably Works

Here's the part most people miss: ashwagandha's main effect on T is probably indirect, via cortisol reduction. It reliably lowers perceived stress and measured cortisol across multiple RCTs, and since chronic cortisol suppresses the HPG axis, pulling cortisol down gives T room to rise.

There's also limited evidence for direct effects on Leydig cell function and LH pulsatility, but those are much less established than the cortisol pathway. More on that relationship in cortisol, stress, and testosterone.

How to Dose It

The clinical dose range is 300 to 600 mg/day of a standardized extract, ideally KSM-66. Split it into two doses (morning and evening) or take it once a day, whichever is easier to remember. Consistency matters more than timing. Most studies ran 8 to 16 weeks before any meaningful changes showed up.

Take with food to avoid mild GI upset. Some people find it sedating, so if that's you, lean the dose toward evening.

Side Effects and Cautions

Ashwagandha is generally well-tolerated, but:

Thyroid. It can mildly raise T3 and T4. Usually a neutral effect, but if you have hyperthyroidism or you're on thyroid meds, talk to your doctor first.
Sedation. Some people feel overly relaxed or groggy. Lower the dose, or just take it in the evening.
Autoimmune conditions. It's immunostimulating, so if you have lupus, MS, or rheumatoid arthritis, check with your physician.
Pregnancy. Not for pregnant or nursing women.
Medications. Can interact with sedatives, thyroid meds, immunosuppressants, and some blood pressure meds.

Does It Work for Everyone?

No. The pattern across studies is pretty consistent: ashwagandha helps most when cortisol is high, sleep is poor, or baseline T is already suppressed. A young, already-fit, low-stress guy with normal T isn't going to see dramatic changes.

If you're in the group most likely to benefit (stressed, mid-aged, sedentary, poor sleep) and you're also fixing the real root causes like sleep, training, and stress, ashwagandha is a reasonable add-on. Not a substitute for the basics.

Quality Matters

The ashwagandha market is the wild west. Many cheap products are under-dosed, contain contaminants, or use leaf material when the research is on root. Look for:

Standardized to at least 5% withanolides.
KSM-66 or Sensoril clearly labeled (not just "ashwagandha extract").
Third-party tested: USP, NSF, or Informed Choice.
Around 600 mg per serving.

Cycling?

Most research uses continuous daily dosing for 2 to 4 months. Whether long-term use is fine is honestly unclear, because the longest trials only run about 6 months. A reasonable approach: 3 months on, 1 month off, retest bloodwork, and see if it's actually moving anything for you personally.

Quick Takeaways

Ashwagandha modestly raises T (~10-18%) in stressed or mid-aged men. Less effect in young healthy men.
Effect is probably mediated through cortisol reduction.
Dose: 600 mg/day KSM-66 for 8-16 weeks. Consistency matters.
Generally safe. Watch thyroid, autoimmune conditions, and med interactions.
Not a substitute for sleep, training, and fixing deficiencies. An add-on at best.

Not medical advice. Ashwagandha interacts with several medications. Talk to your doctor, especially if you take thyroid meds, immunosuppressants, or sedatives.