What Not to Take With Ashwagandha (and What Is Safe)

Ashwagandha may interact with thyroid hormone, sedatives, anticonvulsants, diabetes and blood pressure medicines, and immunosuppressants^{1, 2}. For most other supplements, including magnesium, no interaction is documented, but almost none has been tested with it.

No trial was designed to test ashwagandha with these drugs. The warnings below come from NIH and cancer-center notes, case reports and lab studies. Our ashwagandha page covers benefits, dose and safety on its own.

None of this is an absolute rule, but six groups need a clinician's approval first. Five are named as possible interactions by NIH, NCCIH or Memorial Sloan Kettering^{1, 2, 3}, and none comes from a trial of the pair. The sixth is our own precaution.

• Thyroid hormone medicine such as levothyroxine: ashwagandha may raise thyroid hormone levels².
• Sedatives, benzodiazepines, barbiturates and anticonvulsants: additive drowsiness is possible^{3, 1}.
• Immunosuppressants: NCCIH lists them, and one transplant case raises the concern^{1, 4}.
• Diabetes medicines: a small blood sugar drop is possible^{2, 5}.
• Blood pressure medicines: NIH lists them, and we found one small trial in people with hypertension^{2, 6}.
• Our precaution: anything else that can injure the liver, such as alcohol and other herbs, based on case reports rather than a listed interaction^{7, 8}.

Digoxin blood tests are a separate issue. Ashwagandha can distort some assays, so tell the lab you take it^{3, 9, 10}.

Not without telling your prescriber, because ashwagandha can change thyroid blood tests. The NIH fact sheet says the findings "suggest that ashwagandha might interact with thyroid hormone medications"². NCCIH does not recommend it for people with thyroid disorders¹.

Why is ashwagandha called bad for the thyroid?

Three lines of evidence, one of them mixed:

• Raises T4 in trials. A 2018 trial randomized 50 adults with subclinical hypothyroidism (TSH 4.5 to 10 µIU/L) to 600 mg a day or placebo for 8 weeks. Versus placebo, TSH fell (p < 0.001) and T3 and T4 rose (p = 0.0031 and p = 0.0096)¹¹.
• A small, post-hoc signal in a bipolar trial. In an 8-week trial of 60 people, thyroid tests were only a safety check. The 3 ashwagandha patients with an abnormal thyroid result all had T4 rise (by 7%, 12% and 24%), while 6 of 7 on placebo had it fall¹². A 2026 meta-analysis of 23 trials in 1,706 adults found no change in TSH or T3 and a modest T4 rise (0.61 µg/dL)¹³.
• Case reports of overactive thyroid. Three women aged 32 to 73 developed thyrotoxicosis on ashwagandha extract, and it resolved in all three after stopping. One took 1,950 mg a day for over 2 months². A 47-year-old man had painless thyroiditis after 2 months, and it improved after stopping¹⁴.

If you take thyroid medicine, a rising T4 could push you toward too much hormone, which is why the NIH flags the interaction². Ask for a TSH recheck after starting. See our ashwagandha and thyroid page, the Hashimoto's page and our guide to levothyroxine and supplements.

Treat it as an additive sedative. Memorial Sloan Kettering says people taking benzodiazepines, anticonvulsants or barbiturates should likely avoid ashwagandha because it may have sedative and GABA-related effects, though the clinical relevance is not yet determined³. That evidence is from animals.

The human signal is drowsiness. A review of 30 human trials found somnolence, epigastric discomfort and loose stools were the most common side effects (over 5%)¹⁵. In a 12-week trial of 66 people with schizophrenia, somnolence was more common with ashwagandha than placebo¹⁶.

No study we found tested ashwagandha with alcohol, valerian, kava or melatonin. A reported case of acute steatohepatitis involved high-dose ashwagandha, other supplements, alcohol and several medicines^{7, 3}. It cannot show that any one of them caused it. A 20-year-old man in Japan developed liver injury on ashwagandha plus several antianxiety drugs².

Possibly, but it is unproven either way, so tell your prescriber. Neither NIH nor NCCIH lists antidepressants as an interaction^{2, 1}, and we found no study that measured ashwagandha's effect on antidepressant blood levels.

• Supportive, but not an interaction study: 30 people with obsessive-compulsive disorder already on SSRIs took 120 mg a day for 6 weeks. Yale-Brown scores fell by a median of 8 points versus 2 on placebo, with no adverse events¹⁷.
• Cautionary reports: a review of 1,816 antidepressant adverse-event reports tied ashwagandha to side effects with reboxetine, sertraline (severe diarrhea), escitalopram and paroxetine. Reports cannot show how common these are¹⁸. Memorial Sloan Kettering also lists a woman who used ashwagandha, medical marijuana and an SNRI and developed reversible cerebral vasoconstriction syndrome, which the combination cannot be blamed for³.

We found no ashwagandha data for fluoxetine (Prozac) or bupropion (Wellbutrin). Our guide to SSRIs and supplements covers this in more detail.

NIH and NCCIH name both drug classes as possible interactions^{2, 1}, and the blood pressure group includes ACE inhibitors, beta blockers, calcium channel blockers and diuretics. The human effects are small. A meta-analysis of 11 trials in 667 people found ashwagandha changed fasting glucose by -3.09 mg/dL (95% CI -5.61 to -0.58), with very low certainty and an inconclusive HbA1c result⁵.

For blood pressure, a 60-day trial in 60 people with stress, anxiety and hypertension (300 mg twice daily) reported favorable trends and no serious adverse events⁶. It did not say whether participants took blood pressure medicine.

If you take either type of medicine, check your readings more often in the first weeks. Our high blood pressure and diabetes pages cover the conditions.

Avoid it unless your specialist agrees. NCCIH does not recommend ashwagandha for people with autoimmune disorders¹, and Memorial Sloan Kettering says it may trigger or worsen autoimmune disease³.

The strongest warning is one case. A 69-year-old kidney transplant recipient on tacrolimus, mycophenolate and prednisone took about 1 g of ashwagandha a day for 14 days, then presented with severe tubulointerstitial nephritis, with acute T cell-mediated rejection or drug-related nephritis in question. The graft was later removed. The authors proposed that an immune-stimulating effect triggered rejection, based on mouse data, and noted that no human study has tested it⁴. A single case cannot prove cause.

A 2025 scoping review of 469 studies listed ashwagandha among 15 herbs with the most extensive evidence (human, animal and lab combined) of immune-stimulating properties¹⁹. See autoimmune disease and autoimmune health.

Liver injury is the main documented harm, and it is rare. NIH reports a few serious cases, some in people with pre-existing liver disease. In five cases, products with 450 to 1,350 mg a day caused signs after 1 week to 4 months².

• US and Iceland, 5 cases: jaundice, nausea, lethargy and itching began 2 to 12 weeks after starting. Injury was cholestatic or mixed. Liver tests normalized in 1 to 5 months in four patients, and none developed liver failure. Four took other supplements, and rhodiola was a possible co-cause in one⁸.
• India, 23 cases: 8 took single-ingredient products. Five of those 8 had chronic liver disease, and 3 of the 5 developed acute-on-chronic liver failure and died²⁰.
• Other case reports: MSK lists skin rash as a less common effect and describes a man with burning, itching and skin discoloration, and a 55-year-old woman who needed continued hydrocortisone after prolonged use³.

Anyone with liver disease should skip it. For feeling emotionally flat on ashwagandha, see our emotional numbness page. See our liver health page, our guide to Tylenol and supplements and the rhodiola page.

Through three axes: stress, thyroid and sex hormones. A 2026 meta-analysis of 23 randomized trials found ashwagandha lowered cortisol (standardized mean difference -1.18), raised T4 modestly and raised testosterone in men by 57.43 ng/dL but not in women (5.09 ng/dL). Estradiol did not change¹³.

That is why NCCIH says men with hormone-sensitive prostate cancer should avoid it¹. Our testosterone page has more on the testosterone data.

Several groups are told to avoid it, whatever else they take:

• Pregnancy and breastfeeding: NCCIH and MSK say avoid in pregnancy, and NCCIH says do not use while breastfeeding^{1, 3}. The miscarriage evidence is disputed: the American Herbal Pharmacopoeia says its report was misrepresented. Denmark banned ashwagandha in 2023, and France's agency advised against it in pregnancy, breastfeeding and endocrine disorders in 2024².
• Before surgery: NCCIH does not recommend it¹.
• Thyroid or autoimmune disorders: NCCIH does not recommend it¹.

Very little has been tested, and none of this proves safety:

• Magnesium: not on NCCIH's list of possible interactions¹, but we found no trial of the pair alone. See ashwagandha and magnesium.
• Psychiatric medicines, under supervision: 60 people with bipolar disorder took 500 mg a day for 8 weeks on top of maintenance medicine, with only minor adverse events²¹. A 12-week trial gave 66 people with schizophrenia 1,000 mg a day with antipsychotics, and somnolence was more common¹⁶. These were efficacy trials with monitoring you will not have at home, not interaction studies.
• Food: the SSRI trial told participants to take capsules preferably after meals¹⁷. Stomach upset, loose stools and nausea are common side effects²². We found no trial comparing fed with fasted dosing.

What about the lab studies on drug metabolism?

They conflict. Extracts inhibited the CYP2B6 enzyme and moderately induced CYP3A4 in liver cells²³, yet showed no significant CYP3A4 or CYP2D6 interaction in liver microsomes²⁴. One root extract changed CYP3A4 expression and activity in human hepatocytes²⁵. Clinical relevance has not been determined³.

We found no study that paired ashwagandha with any of these, so none can be called safe or unsafe on evidence. None appears on the NIH or NCCIH interaction lists^{2, 1}. The most careful reading:

• Melatonin or L-theanine: both are used for sleep or calm, so add one at a time and watch for daytime drowsiness. See the melatonin and L-theanine pages.
• Berberine: start one at a time if you take diabetes medicine. See berberine.
• Hormonal birth control: no trial has paired them. Our birth control and herbs guide covers the enzyme data.
• Stimulants such as Adderall: we found no data. Ask the prescriber.

Use this decision rule before starting:

• No medicines, healthy liver, not pregnant: a short course of up to about 3 months is the range with evidence². Start one new supplement at a time.
• Thyroid, diabetes, blood pressure, sedative, anticonvulsant or immune-suppressing medicine: ask your prescriber or pharmacist first, and arrange a blood test or home readings.
• Doses and products: ashwagandha is sold as a dietary supplement, which the FDA does not approve before sale¹, and NIH says trials used varied extracts and doses, so recommended amounts are hard to identify².
• Digoxin: tell the lab and prescriber before a level is drawn⁹.
• Jaundice, dark urine or itching: stop and seek care.

We searched PubMed through a research index, NIH Office of Dietary Supplements, NCCIH and Memorial Sloan Kettering on 2 November 2026. We read the records of 21 journal papers (meta-analyses, randomized trials, case series, case reports and lab studies) and four web fact sheets, and cited all of them. We prioritized systematic reviews and human data. No trial tested ashwagandha with the drugs people ask about, so most interaction guidance rests on expert fact sheets, case reports and lab work. This article was checked by a separate AI reviewer against its sources, not by a clinician.

1. National Center for Complementary and Integrative Health. Ashwagandha: Usefulness and Safety. https://www.nccih.nih.gov/health/ashwagandha
2. National Institutes of Health, Office of Dietary Supplements. Ashwagandha: Is it helpful for stress, anxiety, or sleep? Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Ashwagandha-HealthProfessional/
3. Memorial Sloan Kettering Cancer Center. Ashwagandha (Information About Herbs, Botanicals and Other Products). https://www.mskcc.org/cancer-care/integrative-medicine/herbs/ashwagandha
4. Sriperumbuduri S, et al. Ashwagandha and Kidney Transplant Rejection. Kidney Int Rep. 2020;5(12):2375-2378. doi:10.1016/j.ekir.2020.09.024
5. Farrin N, et al. The effects of Ashwagandha (Withania somnifera) supplementation on fasting blood glucose and HbA1c: a systematic review and dose-response meta-analysis of randomized controlled trials. Diabetes Res Clin Pract. 2026;241:113529. doi:10.1016/j.diabres.2026.113529
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13. Fornalik M, et al. Hormonal Modulation with Withania somnifera: Systematic Review and Meta-Analysis of Randomized-controlled Trials. Planta Med. 2026;92(8):790-805. doi:10.1055/a-2802-8363
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