Evidence explainerAshwagandhaMagnesiumL-theanine

Ashwagandha Interactions: Thyroid Medicine, Sedatives, SSRIs, Alcohol, Magnesium and L-Theanine

NIH lists five drug classes that may interact with ashwagandha, led by thyroid hormone. For SSRIs, stimulants and alcohol there are no trials, only case reports and an additive-drowsiness logic. Here is what is known for each.

By Kymata Labs EditorialPublished October 11, 2026Last reviewed October 11, 2026

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

Key takeaways

  • NIH's Office of Dietary Supplements says ashwagandha might interact with thyroid hormone medicines, antidiabetes medicines, blood pressure medicines, immunosuppressants and sedatives [1].
  • Thyroid is the best-documented concern: in an 8-week trial, 600 mg a day of root extract raised T3 and T4 and lowered TSH versus placebo, and three cases of thyrotoxicosis resolved after stopping ashwagandha [1][2].
  • There are no controlled trials of ashwagandha with SSRIs such as sertraline or escitalopram; a Polish chart review of adverse-event reports linked the combination to cases of diarrhea, muscle pain, nausea and restless legs [3].
  • Drowsiness is a common side effect, so stacking ashwagandha with alcohol, benzodiazepines or sleep medicines is the obvious additive risk, even though no trial has measured it [1].
  • Neither NIH fact sheet lists an interaction between ashwagandha and magnesium or L-theanine; the bigger question with those stacks is the total sedative load and the label doses [1][4].

The evidence, graded

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

  • Grade CImprovedAnxiety scores (HAM-A)Ashwagandha · Meta-analysis · n=254 · 2024 · PMID 39083548Hamilton Anxiety scores fell by 5.96 points versus placebo; sleep onset, total sleep time, sleep quality and efficiency also improved. Heterogeneity was extreme (I² 98%).
  • Grade BImprovedOverall sleepAshwagandha · Meta-analysis · n=400 · 2021 · PMID 34559859Small but significant improvement in overall sleep (SMD -0.59), larger in people with insomnia. Mental alertness on rising and anxiety also improved; quality of life did not. No serious side effects reported.

The official list: five medicine classes

The NIH fact sheet names thyroid hormone medicines first, then antidiabetes medicines, antihypertensives, immunosuppressants and sedatives as possible interactions [1]. These are flagged on mechanism and case reports rather than on interaction trials, so 'possible' is the honest word [1].

The logic for each, in plain terms:

  • Thyroid medicines (levothyroxine): ashwagandha may push thyroid hormone levels up, so the combination could overshoot [1][2].
  • Diabetes medicines: ashwagandha is listed as a possible interaction, so glucose readings deserve a closer look when starting or stopping it [1].
  • Blood pressure medicines: also listed; home readings are worth watching for the same reason [1].
  • Immunosuppressants (for transplants or autoimmune disease): listed by NIH; anyone on these should not start an herb without their care team [1].
  • Sedatives (benzodiazepines, sleep medicines): drowsiness is a known side effect, so effects may add up [1].

Ashwagandha and levothyroxine

In a small Indian trial of 50 adults with subclinical hypothyroidism, 600 mg a day of ashwagandha root extract for 8 weeks improved TSH, T3 and T4 compared with placebo [2]. That is a real hormonal effect, which is exactly why it matters for someone whose dose of thyroid hormone is already set [1].

NIH also cites three case reports of thyrotoxicosis in women aged 32 to 73 taking ashwagandha, one at an unusually high 1,950 mg a day for more than 2 months; symptoms resolved after stopping in all three [1]. If you take levothyroxine and want to try ashwagandha, ask your prescriber about rechecking thyroid levels after a few weeks [1]. More detail is in ashwagandha side effects: liver, thyroid and pregnancy.

Ashwagandha with Lexapro, Zoloft and other antidepressants

No randomized trial has tested ashwagandha alongside an SSRI, so the evidence is limited to adverse-event reports [3]. A 2023 chart review from Kraków evaluated 1,816 adverse-event reports and found adaptogens involved in 9% of events where antidepressants were combined with other preparations [3].

For ashwagandha specifically, the reviewers linked sertraline to severe diarrhea, escitalopram to muscle pain, stomach pain, nausea, vomiting, restless legs and cough, and paroxetine to muscle and eye pain with raised eye pressure [3]. Case reports cannot prove cause, but they are a reason to start antidepressant-plus-herb combinations only with the prescriber in the loop [3].

Adderall, alcohol and other everyday combinations

There are no published interaction studies of ashwagandha with Adderall or other stimulants, and no official warning for the pair [1]. People often take ashwagandha to blunt stimulant jitters; the honest status is 'unstudied', and ADHD medicine changes belong with the prescriber.

Alcohol has no specific study either, but ashwagandha commonly causes drowsiness and alcohol is a sedative, so the effects can stack [1]. Rare liver injury has also been reported with ashwagandha, which is one more reason not to pair it with heavy drinking [1].

Ashwagandha with magnesium or L-theanine

Ashwagandha, magnesium and L-theanine are often sold together for sleep and stress. Neither NIH fact sheet lists an interaction between ashwagandha and magnesium, and no interaction with L-theanine has been described in the sources we reviewed [1][4]. The practical points are dose and timing: supplemental magnesium has a 350 mg daily upper limit for adults [4], and both ashwagandha and magnesium are marketed for sleep, so taking them together in the evening is common.

For the evidence behind each, see does ashwagandha work for stress and sleep, L-theanine for anxiety and sleep and magnesium for anxiety.

Who should skip it regardless of medicines

Some experts advise against ashwagandha in pregnancy, Denmark banned it in 2023, and France's food-safety agency advised against it in pregnancy, breastfeeding and endocrine disorders in 2024 [1]. Experts cited by NIH say it may not be safe for men with hormone-sensitive prostate cancer because it may raise testosterone [1]. Trials support tolerability for about 3 months; longer-term safety is unknown [1].

Before combining any supplement with prescription medicine, run it through our interaction checker and confirm with a pharmacist.

Quick answers

Can I take ashwagandha with levothyroxine?

Only with your prescriber's input. Ashwagandha changed TSH, T3 and T4 in a placebo-controlled trial, and thyrotoxicosis has been reported [1][2].

Can you take ashwagandha with Lexapro or Zoloft?

It has not been studied in trials. Adverse-event reports link the combinations to diarrhea, muscle pain, nausea and restless legs, so involve your prescriber before adding it [3].

Is it safe to drink alcohol while taking ashwagandha?

There is no specific study. Drowsiness is a common ashwagandha side effect and rare liver injury has been reported, so combining it with alcohol is not a good idea [1].

Can I take ashwagandha and magnesium together?

Neither NIH fact sheet lists an interaction between them [1][4]. Keep supplemental magnesium within the 350 mg daily adult upper limit [4].

Does ashwagandha interact with birth control?

No interaction with hormonal contraception is listed by NIH; the official list covers thyroid, diabetes, blood pressure, immunosuppressant and sedative medicines [1]. Ask a pharmacist if you are unsure.

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References

  1. [1]Ashwagandha: Is it helpful for stress, anxiety, or sleep? Fact Sheet for Health Professionals (updated May 2, 2025; accessed October 11, 2026). NIH Office of Dietary Supplements, 2025.
  2. [2]Efficacy and Safety of Ashwagandha Root Extract in Subclinical Hypothyroid Patients: A Double-Blind, Randomized Placebo-Controlled Trial. Journal of Alternative and Complementary Medicine, 2018. PMID 28829155
  3. [3]Harder, better, faster, stronger? Retrospective chart review of adverse events of interactions between adaptogens and antidepressant drugs. Frontiers in Pharmacology, 2023. PMID 37829299
  4. [4]Magnesium: Fact Sheet for Health Professionals (updated January 6, 2026; accessed October 11, 2026). NIH Office of Dietary Supplements, 2026.

Ashwagandha and other dietary supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA. Talk to your clinician or pharmacist before starting a supplement, especially if you take prescription medicines. This page has no product or affiliate links.

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