Evidence explainerAshwagandha

Ashwagandha Side Effects: The Liver, Thyroid and Pregnancy Warnings Behind Denmark’s Ban

Most people in trials tolerated ashwagandha fine for a few months. But a handful of rare, real risks explain why one European country banned it and others issued warnings.

By Kymata Health editorial teamPublished October 9, 2026Last reviewed October 9, 2026

Medical review pending. Written by our editorial team from the studies cited below; a credentialed clinician has not reviewed it yet. Educational only, not medical advice.

Key takeaways

  • In trials, the common side effects were mild: stomach upset, loose stools, nausea and drowsiness [1].
  • Rare liver injury has been reported; in a 5-case series, jaundice and itching started 2 to 12 weeks after starting and liver tests normalized 1 to 5 months after stopping [2].
  • An 8-week trial at 600 mg/day changed thyroid hormone levels (TSH, T3, T4) compared with placebo, and thyrotoxicosis has been reported [3][1].
  • Denmark banned ashwagandha in 2023, and France’s food-safety agency advises against use in pregnancy and breastfeeding [1].

The evidence, graded

Pulled from our monograph evidence tables. Grades follow our evidence-grading policy.

  • Grade BImprovedPerceived stressAshwagandha · Meta-analysis · n=1,002 · 2022 · PMID 36017529Stress (SMD -1.75) and anxiety (SMD -1.55) fell versus placebo. Heterogeneity was very high (I² 83–94%) and certainty of evidence was low.
  • Grade CNo effectFatigue and vigor in older menAshwagandha · Crossover RCT · n=57 · 2019 · PMID 30854916Fatigue, vigor and sexual well-being improved over time in both conditions with no significant difference from placebo. DHEA-S rose 18% and testosterone 14.7% more than with placebo.

The common, mild stuff

NIH reports that across trials the most common side effects were mild stomach upset, loose stools, nausea and drowsiness [1]. Ashwagandha appeared well tolerated in trials of up to about 3 months; safety over many months or years is unknown [1].

Liver: rare but documented

A case series from Iceland and the US Drug-Induced Liver Injury Network described ashwagandha-linked liver injury, typically cholestatic, with jaundice and itching appearing 2 to 12 weeks after starting [2]. In those 5 cases, liver tests returned to normal within 1 to 5 months after stopping [2]. NIH notes some reported cases involved pre-existing liver disease [1].

Seek care promptly for yellowing skin or eyes, dark urine or persistent itching, and talk to your clinician before using ashwagandha if you have a liver condition [1].

Thyroid: it can move your numbers

In an 8-week trial in people with subclinical hypothyroidism, 600 mg/day of root extract changed TSH, T3 and T4 compared with placebo [3]. NIH also describes three cases of thyrotoxicosis and lists thyroid hormone medicines as a possible interaction [1]. Anyone with a thyroid condition or on thyroid medicine should speak with their clinician first and expect lab monitoring [1].

Hormones and pregnancy

In a crossover trial of 57 overweight men aged 40 to 70, testosterone rose 14.7% and DHEA-S 18% more than with placebo, though fatigue and vigor did not differ [4]. Experts cited by NIH say ashwagandha might not be safe for men with hormone-sensitive prostate cancer [1].

A 2020 Danish risk assessment raised concerns about possible effects on pregnancy and on thyroid and sex hormones, and Denmark banned ashwagandha in 2023 [1]. France’s food-safety agency (ANSES, 2024) recommends against use while pregnant or breastfeeding and by people with endocrine disorders, while the American Herbal Pharmacopoeia disputes the evidence for harm in pregnancy [1].

Medicines to mention to your pharmacist

NIH lists possible interactions with thyroid hormone, antidiabetes, blood pressure, immunosuppressant and sedative medicines [1]. Drowsiness is a common side effect, which matters if you also take sedatives [1].

For what ashwagandha may do, see ashwagandha for stress and sleep. If thyroid or liver concerns rule it out for you, magnesium is a common alternative people compare it with: magnesium glycinate vs citrate. Full safety details are on the ashwagandha monograph.

Quick answers

Why did Denmark ban ashwagandha?

A 2020 Danish risk assessment raised concerns about possible effects on pregnancy and on thyroid and sex hormones; the ban followed in 2023 [1].

Can ashwagandha damage your liver?

Rarely. Published cases describe cholestatic liver injury that resolved within 1 to 5 months after stopping [2].

Keep reading

Full monographs

Related articles

Browse the full Supplement & Nutrient Encyclopedia or all supplement articles.

References

  1. [1]Ashwagandha: Is it helpful for stress, anxiety, or sleep? Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2025.
  2. [2]Ashwagandha-induced liver injury: A case series from Iceland and the US Drug-Induced Liver Injury Network. Liver Int, 2020. PMID 31991029
  3. [3]Efficacy and Safety of Ashwagandha Root Extract in Subclinical Hypothyroid Patients: A Double-Blind, Randomized Placebo-Controlled Trial. J Altern Complement Med, 2018. PMID 28829155
  4. [4]A Randomized, Double-Blind, Placebo-Controlled, Crossover Study Examining the Hormonal and Vitality Effects of Ashwagandha ( Withania somnifera) in Aging, Overweight Males. Am J Mens Health, 2019. PMID 30854916

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