Disclosure: This article may contain affiliate links. If you buy through these links, we may earn a commission at no extra cost to you. Our recommendations are based on editorial criteria, not commission rates.

Evidence-informedFocus: ashwagandha benefitsReview priority: High

———————————————– | —————————— | ——————————- |

KSM-66 (root extract, 5% withanolides)300 mg twice daily600 mg/day
Sensoril (root and leaf extract, 10% withanolides)125–250 mg once or twice daily125–500 mg/day
Shoden (concentrated extract, 35% withanolides)120–240 mg once daily120–240 mg/day
Raw root powder3,000–5,000 mg/dayLess consistent bioavailability

The KSM-66 extract (300 mg twice daily = 600 mg/day) is the most replicated dose in the stress and sleep literature. Sensoril uses a different extraction method and a broader withanolide spectrum (including leaf withanolides), with slightly lower mass doses but potentially comparable effect.

What form to choose

Standardized extracts are significantly more reliable than raw root powder because withanolide content in raw powder varies by soil, growing conditions, harvest time, and storage.

  • KSM-66: The most studied extract for stress, sleep, and physical performance. Uses only root material. Extensively published.
  • Sensoril: Also well-studied; uses root and leaf material. Slightly lower typical dose.
  • Shoden: Newer, higher withanolide concentration (35%), fewer but promising trials.
  • Raw root powder: Lower cost but inconsistent potency.

When buying, look for the specific extract name (KSM-66 or Sensoril) on the supplement facts panel rather than just "ashwagandha root extract." Generic extracts without named sources have no way to verify withanolide content.

How long before it works

Most clinical trials report significant effects at 8–12 weeks of consistent daily use. Some people notice reduced stress reactivity and improved sleep quality within 2–4 weeks, but the full cortisol-modulating effect tends to build over time.

Ashwagandha is not a sedative or an anxiolytic drug. It does not produce an immediate relaxing effect the way benzodiazepines or alcohol do. Its benefit accumulates through sustained HPA axis modulation.

Side effects

At doses used in clinical trials, ashwagandha is generally well tolerated. Reported side effects include:

  • Mild gastrointestinal upset (nausea, loose stools) — usually resolves with food
  • Drowsiness, particularly at higher doses — take in the evening if this occurs
  • Rarely: headache, allergic reactions

More serious but rare:

  • Liver injury: Case reports of hepatotoxicity (liver damage) associated with ashwagandha supplements have been published. The mechanism is unclear and may relate to product adulteration or idiosyncratic reactions in susceptible individuals. People with liver disease should avoid ashwagandha.
  • Thyroid stimulation: Ashwagandha may increase T3 and T4 thyroid hormone levels. For people with hyperthyroidism or on thyroid medication (levothyroxine), this can cause hyperthyroid symptoms.

Who should avoid ashwagandha

  • Pregnant women: Ashwagandha has traditionally been used to induce abortion in some Ayurvedic applications. Its safety in pregnancy is not established.
  • Thyroid disease: May raise thyroid hormone levels; check with your endocrinologist or prescriber if you have hypothyroidism or hyperthyroidism.
  • Autoimmune conditions: Ashwagandha stimulates immune function. People with autoimmune conditions (lupus, multiple sclerosis, rheumatoid arthritis) or taking immunosuppressants should consult their physician.
  • Nightshade sensitivity: Ashwagandha is a member of the Solanaceae (nightshade) family. People with nightshade allergies may react.
  • Surgery: Ashwagandha may affect anesthesia. Stop at least 2 weeks before scheduled surgery.
  • Sedative medications: Ashwagandha has mild sedative properties. Combining with prescription sedatives, sleep medications, or alcohol may cause additive sedation.

Practical use guidance

For stress reduction: 300 mg KSM-66 or 250 mg Sensoril taken in the morning or split morning/evening. Consistent daily use for at least 8 weeks to assess benefit.

For sleep improvement: 300 mg KSM-66 or 120–240 mg Shoden taken 30–60 minutes before bed. The mild sedative quality is better used in the evening for this purpose. L-theanine and magnesium glycinate are frequently combined with ashwagandha in sleep stacks for complementary mechanisms.

For exercise performance: 300 mg KSM-66 twice daily around training periods; best studied in combination with a resistance training program.

Frequently Asked Questions

Does ashwagandha actually reduce cortisol?
Yes. Multiple randomized controlled trials using the KSM-66 and Sensoril extracts have shown statistically significant reductions in serum cortisol (20–30%) compared to placebo after 8–12 weeks. This is one of the more robustly documented effects of any adaptogen.
How long does ashwagandha take to work?
Most people need 6–12 weeks of consistent daily use to see meaningful improvements in stress, cortisol, or sleep measures. Some report feeling less reactive to stress within 2–4 weeks, but the most clinically relevant cortisol changes appear at 8–12 weeks in published trials.
Is KSM-66 the best ashwagandha?
KSM-66 has the most published clinical trial data of any ashwagandha extract and is the gold standard for root-only standardized extracts. Sensoril is also well-studied and uses a different proprietary process. Both are meaningfully superior to generic "ashwagandha root extract" products with no named source and unverified withanolide content.
Can ashwagandha help with anxiety?
Yes. Multiple trials using validated anxiety scales (HAM-A, GAD-7, DASS-21) have found significant reductions in anxiety scores with ashwagandha supplementation over 8–12 weeks. The effect is consistent with its cortisol-reducing and HPA axis modulating properties. Ashwagandha is not a treatment for anxiety disorder — it is a supplement that may reduce anxiety symptoms in the context of chronic stress.
Does ashwagandha affect hormones?
Yes. Ashwagandha modestly increases testosterone in men (particularly those with stress-suppressed testosterone), may increase thyroid hormones, and in women has been studied for hormonal balance in perimenopause with some positive results. These effects mean it should be used carefully by people with thyroid disease or hormone-sensitive conditions.
Can I take ashwagandha every day?
Most clinical trials ran 8–12 weeks with daily use. Some people use it for longer periods, but robust safety data beyond 3 months is limited. Cycling (e.g., 8–12 weeks on, 4 weeks off) is sometimes recommended by integrative practitioners, though there is no clinical evidence requiring it. If you notice any changes in thyroid symptoms or liver-related symptoms (jaundice, dark urine, fatigue), stop and consult your provider.
Is ashwagandha safe with antidepressants?
No strong evidence of a dangerous interaction exists, but ashwagandha has mild GABA-modulating and serotonin-related properties. If you take SSRIs, SNRIs, or other psychiatric medications, discuss ashwagandha with your prescriber or pharmacist before starting.
Does ashwagandha cause weight gain or weight loss?
Ashwagandha does not directly cause significant weight changes in either direction. Some trials show modest reductions in body weight and food cravings associated with lower cortisol — chronic high cortisol promotes fat accumulation particularly around the abdomen. Any weight effects are indirect and secondary to stress reduction.

Bottom line

Ashwagandha has more randomized controlled trial support than most herbal supplements. The KSM-66 and Sensoril extracts at evidence-based doses (300–600 mg/day) consistently show meaningful reductions in cortisol, stress perception, and sleep onset time over 8–12 weeks. The main cautions are thyroid disease, pregnancy, autoimmune conditions, and the recently documented (though rare) liver injury risk — which makes buying from brands that use named, quality-tested extracts more important than price comparison. For people managing chronic stress or poor sleep with an otherwise healthy profile, ashwagandha is one of the most credible supplements to consider.

Related Articles

Sources

Educational note: This article is for general health education and is not a substitute for personal medical advice, diagnosis, or treatment.