Ashwagandha: does it work, and how to take it

Does ashwagandha work?

Yes — with qualification. Ashwagandha (Withania somnifera) is one of the better-evidenced adaptogens in the supplement market, carrying a Grade B across its two primary claims: stress/cortisol reduction and sleep quality improvement. It is not a sedative, not a mood drug, and not a one-week fix. What the evidence shows is a reliable, moderate effect on the body's stress-response system, particularly when taken consistently for 6–8 weeks with a standardised extract. The verdict: worth a trial — provided you respect the contraindications.

What ashwagandha is

Ashwagandha is an adaptogen — a plant compound that helps the body modulate its response to physiological and psychological stress rather than forcing a single pharmacological direction. It is derived from the root of Withania somnifera, a shrub native to India and North Africa, and has been used in Ayurvedic medicine for over 3,000 years. The active constituents are primarily withanolides, a class of steroidal lactones that appear to modulate the hypothalamic-pituitary-adrenal (HPA) axis and reduce cortisol output.

Two branded standardised extracts dominate the clinical literature: KSM-66 (root-only, 5% withanolides) and Sensoril (root + leaf, 10% withanolides). Most high-quality RCTs use one of these. Raw ashwagandha powder or leaf-dominant extracts are less well-studied and carry higher contamination risk.

Does it work? The evidence

Stress and cortisol reduction — Grade B

The most robust evidence is here. A 2012 double-blind RCT (Chandrasekhar et al., Indian Journal of Psychological Medicine) gave 64 chronically-stressed adults either 600 mg/day KSM-66 ashwagandha (300 mg twice daily) or placebo for 60 days. The ashwagandha group showed a statistically significant ~27% reduction in serum cortisol and meaningful reductions on the Perceived Stress Scale (PSS) compared to placebo. Effect sizes were clinically meaningful, not merely statistically detectable. Multiple other controlled trials have replicated cortisol and PSS reductions at doses of 300–600 mg/day, giving moderate (Grade B) confidence.

This is not feel-good placebo. Cortisol is a measurable biomarker, and the signal is consistent across several independent trials using validated stress scales.

Sleep quality — Grade B

A secondary but well-supported claim. Separate controlled trials report improved sleep quality at 300–600 mg/day, supporting the Grade B sleep claim. A separate 2020 RCT in PLOS ONE (Langade et al.) — 150 adults, 120-day follow-up, 300 mg twice daily — confirmed improvements in sleep onset latency, total sleep time, and self-reported quality. Grade B: moderate evidence from multiple RCTs, though most are small-to-medium sample sizes.

The sleep benefit likely flows from the cortisol effect (lower evening cortisol = easier sleep onset) plus possible direct GABA-ergic activity of withanolides.

Anxiety reduction — Grade C

Promising but limited. Several trials report reduced anxiety scale scores (Hamilton Anxiety Rating Scale, DASS-21), but the evidence is more heterogeneous and mostly in anxious adults rather than clinical anxiety disorder populations. Grade C: interesting signal, not yet robust enough to lead with. If anxiety is your primary concern, a GP consultation matters more than any supplement.

How to take it

Dose: 300–600 mg/day of a standardised root extract. The 600 mg dose consistently outperforms 250 mg across trials and is the dose to target if you tolerate it. Do not exceed this without medical supervision.

Timing: Take your dose in the evening — ideally 30–60 minutes before bed. This timing aligns with both the sleep-quality benefit and the mild drowsiness side effect, turning a potential inconvenience into a feature. If splitting doses (e.g. 300 mg morning + 300 mg evening), the morning dose is less likely to cause drowsiness.

Form: Always use a standardised extract — KSM-66 or Sensoril are the most clinically validated. Raw powder and leaf-heavy extracts are not equivalent and have a weaker safety profile.

Duration: Ashwagandha is not fast-acting. Allow 6–8 weeks of consistent daily use before judging effectiveness. Most RCTs run for 60–90 days.

With food: Yes — GI tolerance is better when taken with a meal.

Who should take it — and who shouldn't

Most likely to benefit: Adults under sustained stress — demanding training blocks, high-pressure work periods, disrupted sleep, or anyone whose cortisol feels chronically elevated. Athletes in heavy training phases where recovery is lagging may also benefit, as elevated cortisol blunts anabolic signalling. If you are interested in the muscle growth programme or body recomposition, managing chronic stress is part of the equation — ashwagandha can be a useful support tool during intense phases.

Do not take if:

• Pregnant or breastfeeding — insufficient safety data, potential uterotonic effects.
• Thyroid disease (hypo- or hyperthyroidism) — ashwagandha stimulates thyroid hormone production and can interact dangerously with thyroid medications such as levothyroxine.
• Autoimmune conditions (Hashimoto's thyroiditis, rheumatoid arthritis, lupus, multiple sclerosis) — it may stimulate immune activity and worsen autoimmune flares.
• On sedatives (benzodiazepines, sleep medications), immunosuppressants, or thyroid drugs — additive or antagonistic interactions.
• Known liver disease — see safety section.
• Under 18 years old — no adequate safety data.

Safety and interactions

At 300–600 mg/day of standardised root extract, ashwagandha is generally well-tolerated in healthy adults. Common side effects: mild GI upset (nausea, loose stools), drowsiness. These are dose-dependent and tend to diminish after the first 1–2 weeks.

The more serious concern is rare drug-induced liver injury (DILI). A series of published case reports and a 2023 systematic review confirmed a causal link between ashwagandha supplementation and hepatotoxicity in a small number of individuals, with most cases resolving on discontinuation. The mechanism is not fully understood. Stop immediately and seek GP advice if you notice jaundice (yellowing of the skin or eyes), dark urine, right-upper abdominal pain, or unexplained fatigue — these are warning signs of liver stress.

To minimise risk: use root-only extracts (not leaf), buy from brands that provide third-party certificates of analysis showing withanolide content and heavy-metal testing, and do not exceed 600 mg/day.

General information, not medical advice — check with a GP or pharmacist before starting, especially if pregnant, breastfeeding, under 18, or on medication.

How to buy it well

Three things matter when purchasing ashwagandha:

1. Standardised extract — look for KSM-66 (≥5% withanolides) or Sensoril (≥10% withanolides) named on the label. Generic ashwagandha root extract with no withanolide specification is unverified.
2. Third-party testing — request a certificate of analysis (COA) for withanolide content and heavy-metal testing (lead, arsenic, mercury, cadmium). Botanicals sourced from the Indian subcontinent carry higher heavy-metal risk from soil contamination.
3. Root-only — the leaf contains different alkaloid ratios and a less favourable safety profile. Most liver-injury case reports involved products using leaf or whole-plant extracts.

For athletes subject to anti-doping rules, look for Informed-Sport certified products, which test for prohibited substances.

The bigger picture

Ashwagandha is one of the few adaptogens with real human RCT data behind it, and the cortisol + sleep signal is credible. But keep perspective: if your sleep is poor because you are training too hard with inadequate nutrition, or your stress is high because you have no structured recovery protocol, no supplement fixes that. Supplements account for roughly 5% of results — programming, nutrition, sleep habits, and consistency drive the other 95%.

If you want the full picture — not just a supplement recommendation but a training and nutrition plan that actually makes the 95% work — book a free consultation with Lift Republic. Or start with the free Blueprint quiz to get personalised recommendations in under three minutes.

The verdict

Ashwagandha earns its place on the shelf. Grade B across stress reduction and sleep quality is meaningful in a supplement category full of Grade D noise. The 600 mg/day KSM-66 dose is the evidence-backed target; allow 8 weeks; take it in the evening with food. Respect the contraindications — especially thyroid disease, autoimmune conditions, liver history, and pregnancy — and buy a standardised, tested product. For most healthy adults under sustained stress, this is worth a trial.