Ashwagandha for Cortisol and Testosterone: Does It Work, and What to Test

1. The short answer, and what the evidence shows

Unlike most herbal supplements, ashwagandha has a real stack of human randomised controlled trials behind it, not just rodent studies and testimonials. The picture they paint is split cleanly down the middle: the case for lowering cortisol is reasonably strong, and the case for raising testosterone is real but much weaker and narrower.

On the cortisol side, a 2019 randomised, double-blind trial in the journal Medicine gave 60 stressed adults 240 mg of a standardised extract daily for 60 days and recorded a 23% fall in morning cortisol versus placebo. On the testosterone side, an 8-week trial in the Journal of the International Society of Sports Nutrition found that young men doing resistance training on 600 mg a day gained noticeably more testosterone than the placebo group.

That is a better evidence base than fenugreek, tribulus or most “test boosters” can show. But the effects depend heavily on who you are, how stressed you are, and what you are starting from, which is exactly the part the adverts flatten. The practical takeaway: ashwagandha can move two numbers a blood test reads, and whether it moves yours is an empirical question you can answer rather than guess at. For how it sits against the rest of the cabinet, see our review of testosterone booster supplements.

2. Two different jobs: cortisol and testosterone

Ashwagandha is marketed as one thing but is really being asked to do two separate jobs, and they have different amounts of evidence behind them. Keeping them apart is the key to reading the research honestly.

Notice what both jobs have in common: each one changes a marker you can put on a blood test. Cortisol, total testosterone and DHEA-S are the exact things a stress-and-hormone panel measures. That is unusual for a supplement, and it is what makes a before-and-after trial worth running instead of judging from how you feel, which is the least reliable readout of all.

3. What it does to cortisol (the stronger case)

This is where ashwagandha has its best evidence. Several randomised, placebo-controlled trials in stressed adults report a genuine fall in cortisol, and they broadly agree with each other, which is more than you can say for most supplement research. A 2025 systematic review and meta-analysis that pooled 15 trials found a statistically significant reduction in cortisol at eight weeks, which is the kind of converging result no single study can give you.

The 2019 trial in Medicine is the cleanest single example: 240 mg of a standardised root extract once a day for 60 days lowered morning cortisol by 23%, against a small rise in the placebo group, alongside lower self-reported anxiety. A separate 2019 study in Cureus using 600 mg a day of a different standardised extract for eight weeks also reported a significant reduction in serum cortisol, plus improvements in perceived stress and sleep quality.

Two things are worth holding onto. First, the effect is largest in people who are stressed; in calm, unstressed adults there is far less cortisol to bring down, so the change is smaller. Second, cortisol is a moving target: it swings through the day and rises with everything from a bad night to a hard week, so a single reading is a snapshot, not a verdict. That is exactly why measuring the same way, same time, same conditions, before and after matters. Our guide to the cortisol blood test explains how the timing works, and how to lower cortisol naturally covers the bigger, free levers (sleep, caffeine, training load) before any supplement.

One honest caveat the sellers skip: the same trials that lower cortisol often lower DHEA-S too, the adrenal hormone that usually moves the opposite way to stress. It is a reminder that you are nudging a whole system, not turning one dial, and another reason to look at the panel as a whole rather than a single number.

4. What it does to testosterone (and in whom)

Here the evidence is real but thinner, and the size of the effect depends a lot on the group studied. Two trials are usually quoted.

In the resistance-training trial, 57 young men new to lifting took 600 mg a day for eight weeks while following a training programme. The ashwagandha group’s testosterone rose by about 96 ng/dL, against roughly 18 ng/dL on placebo, and they also gained more strength and muscle. In a 2019 trial in overweight men aged 40 to 75 with mild fatigue, eight weeks of supplementation was linked to about 15% higher salivary testosterone and 18% higher DHEA-S than placebo, although that same study found no significant change in cortisol.

The newest entry is a useful reality check. A 2026 randomised, double-blind, placebo-controlled trial in Frontiers in Reproductive Health gave 76 healthy men 300 mg of root extract twice a day for eight weeks. It saw clear gains in sexual function and semen quality, but the rise in total and free testosterone did not reach statistical significance against placebo, and the authors were careful to call the hormone findings exploratory rather than confirmatory. It is a good example of why the headline “raises testosterone” deserves the caution above: even a well-run 2026 trial could not pin that number down.

Read those together and the pattern is: a modest testosterone nudge that is clearest in men who are training, ageing, or starting from a low or stressed baseline, and much less certain in healthy men who are already mid-range and feeling fine. This is not a substitute for the big levers. The free, high-impact moves, losing visceral fat, sleeping properly, cutting heavy drinking, come first; our guide to raising testosterone naturally ranks them by effect size, and our look at Tongkat Ali applies the same measure-don’t-guess logic to the other herb of the moment.

Which raises the obvious question almost nobody asks before buying: are you actually low, or stressed, in the first place? Plenty of men assume low testosterone on the strength of fatigue or a stalled gym plan when the real driver is sleep, body fat or stress. A test tells you your starting point; a supplement cannot.

5. The safety caveats the listicles leave out

Ashwagandha is well tolerated by most people in short trials, but “natural” does not mean “risk-free”, and a few things are worth knowing before you start:

• Rare liver injury. The NIH LiverTox database records around 23 reported cases of clinically apparent liver injury linked to ashwagandha since 2017, typically appearing 2 to 12 weeks after starting, usually with jaundice and itching. Most recovered fully on stopping, but it is a real, if uncommon, signal. Avoid it if you have existing liver disease.
• It can shift thyroid hormones. Ashwagandha can raise thyroid hormone levels, which is unhelpful if you have an overactive thyroid or take thyroid medication. If your thyroid is a question mark, that is a reason to measure TSH and thyroid function first, not to experiment blind.
• Not in pregnancy. Standard guidance is to avoid ashwagandha entirely during pregnancy. It is also best avoided if you are breastfeeding, given the lack of safety data.
• Sedation and interactions. Because it is calming, it can add to the effect of sedatives, and it may interact with medication for blood pressure, blood sugar, thyroid and immune conditions. Quality also varies: supplements are not regulated like medicines, so dose and purity differ between products.

None of this means ashwagandha is dangerous for most healthy adults. It means the responsible stance is to know your baseline, use a tested standardised product, keep an eye on how you respond, and check with your GP or pharmacist first if you take medication or have a health condition.

6. Check before you start: the markers that matter

Because ashwagandha acts on hormones a blood test reads, it is one of the few supplements where a before-and-after test gives you a real answer rather than a vibe. Take a baseline, run a sensible trial, retest, and compare. The markers worth measuring together are:

• Cortisol— the main stress hormone and ashwagandha’s best-evidenced target, best taken on a morning sample at a consistent time
• Total testosterone— the headline hormone number, best on a fasting morning sample for a fair comparison
• DHEA-S— the adrenal hormone that moved in the trials, often in the opposite direction to what people expect
• Thyroid (TSH)— worth a baseline given ashwagandha can shift thyroid hormones (see our guide to free vs total testosterone for why context markers matter)

Two panels cover this between them. Our General Energy & Wellness panel (£149) measures cortisol alongside thyroid (TSH and Free T4), vitamin D and the core metabolic markers, the broad stress-and-energy picture. If your main interest is the testosterone side, our Complete Male Hormones panel (£119) measures total and free testosterone, SHBG, LH, FSH, prolactin and DHEA-S. Both use a home finger-prick sample analysed by UKAS-accredited UK laboratories. For consistency, take both samples at the same time of day, ideally a fasting morning.

The value of this is not just knowing whether the supplement worked. A baseline can tell you that your cortisol or testosterone was never the problem in the first place, which saves you the money and points you at what actually is. Tests like these measure your hormones and give you a wellness picture; they do not diagnose a condition, and a result that looks off should always be discussed with your GP or a qualified clinician.

7. How to run an honest trial (and stay safe)

If you have a baseline and want to test the herb properly, a few practical points make the result trustworthy:

Run that way, the experiment is honest: a clear baseline, one variable, a long-enough window, and a retest of the same markers. If your morning cortisol has dropped, your testosterone has edged up, and you sleep better, you have your answer. If the numbers are flat after three months, you have saved yourself an open-ended monthly habit, and learned something more useful than any review could tell you. For the stress side specifically, our stress blood test guide covers the wider panel of markers chronic stress moves.

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