Ashwagandha can interact with several categories of medications and is unsafe for certain health conditions. The most significant conflicts involve immunosuppressants, thyroid medications, sedatives, diabetes drugs, and blood pressure medications. If you’re taking any of these, combining them with ashwagandha could amplify side effects or undermine your treatment.
Immunosuppressant Medications
This is one of the most dangerous combinations. Ashwagandha stimulates the immune system by activating key immune cells and increasing their disease-fighting activity. That’s the opposite of what immunosuppressant drugs are designed to do. If you’ve had an organ transplant or take medication to suppress your immune system for an autoimmune condition, ashwagandha can work directly against your treatment.
A case published in Kidney International Reports documented a kidney transplant patient who experienced acute organ rejection after taking ashwagandha. He was on a standard post-transplant regimen of tacrolimus, mycophenolate, and prednisone. Animal research confirmed the mechanism: ashwagandha reversed the immune suppression caused by prednisone and azathioprine, restoring immune activity that these drugs were specifically meant to block. The researchers concluded that ashwagandha causes “loss of peripheral tolerance,” essentially waking up an immune system that medications had intentionally quieted.
Thyroid Medications and Thyroid Conditions
Ashwagandha appears to directly stimulate the thyroid gland to produce and release more thyroid hormone. In mice, it increased levels of the hormone T4 by roughly 111%. For someone with an underactive thyroid already taking levothyroxine, adding ashwagandha can push hormone levels too high. For anyone with an overactive thyroid or Graves’ disease, ashwagandha could make the condition worse.
Multiple case reports document this going wrong. A 73-year-old woman who stopped her levothyroxine and switched to ashwagandha developed thyrotoxicosis, a dangerous excess of thyroid hormone that triggered an abnormal heart rhythm. Her TSH dropped to nearly undetectable levels. Symptoms resolved after she stopped taking ashwagandha. At least two other similar cases have been published.
Adding another layer of risk, researchers have found that some commercially available ashwagandha supplements actually contain measurable amounts of T3 and T4, sometimes exceeding the doses used to treat hypothyroidism. So the risk isn’t only from ashwagandha stimulating your thyroid. Some products may be directly introducing thyroid hormones into your body.
Sedatives, Anti-Anxiety Drugs, and Alcohol
Ashwagandha acts on the GABA system in your brain, the same system targeted by benzodiazepines (like diazepam and lorazepam), barbiturates, and anticonvulsants. GABA is the brain’s main calming neurotransmitter, and drugs that enhance it produce sedation and reduce anxiety. Ashwagandha mimics this effect by acting on both types of GABA receptors and significantly increasing GABA levels in the brain.
Memorial Sloan Kettering Cancer Center advises that patients taking benzodiazepines, anticonvulsants, or barbiturates should avoid ashwagandha because of the potential for additive sedation. The same logic applies to alcohol, which also depresses the central nervous system through GABA pathways. Combining ashwagandha with alcohol could increase drowsiness, impair coordination, and deepen sedation beyond what either substance would cause alone. Ashwagandha may also have additive effects with antidepressants and anti-anxiety medications more broadly, potentially increasing their side effects.
Diabetes Medications
Some clinical studies have found that ashwagandha lowers blood glucose and HbA1c (a marker of long-term blood sugar control) in people with diabetes. The evidence is mixed, with other studies showing no effect, but the possibility is enough to create a real risk. If you’re taking insulin, metformin, or other blood sugar-lowering medications, adding ashwagandha could push your blood sugar too low.
Hypoglycemia symptoms include dizziness, confusion, trembling, sweating, and a rapid heartbeat. If you do combine ashwagandha with diabetes medication, monitoring your blood sugar more frequently is important so you can catch any unexpected drops early.
Blood Pressure Medications
Ashwagandha has a modest but real blood pressure-lowering effect, particularly on diastolic pressure (the bottom number). In one study, supplementation dropped diastolic blood pressure from about 100 mmHg to 85 mmHg. That 15-point reduction is clinically meaningful on its own. Stacked on top of antihypertensive medication, it could cause blood pressure to fall too low, leading to dizziness, fainting, or fatigue.
If you take blood pressure medication and want to try ashwagandha, tracking your readings at home would help you spot any excessive drops.
Pregnancy and Breastfeeding
Ashwagandha is not considered safe during pregnancy. Some reports suggest it may have the ability to cause spontaneous abortion, though the strength of this evidence is debated. A 2020 risk assessment from the Technical University of Denmark flagged both the potential for pregnancy loss and the hormonal disruption ashwagandha can cause. Denmark banned ashwagandha entirely in 2023. France’s food safety agency issued a 2024 recommendation against its use by pregnant women, breastfeeding women, and people with endocrine disorders.
The NIH notes that ashwagandha’s effects on sex hormones and thyroid hormones add additional reasons for caution during pregnancy and breastfeeding, when hormonal stability is especially important.
Liver Health Concerns
A growing number of case reports from Japan, Iceland, India, and the United States document liver injury linked to ashwagandha. These cases typically involve jaundice (yellowing of the skin and eyes), elevated liver enzymes, and in some instances cholestatic hepatitis, where bile flow from the liver is blocked. In one series of five patients, all developed jaundice, and recovery took up to eight months after stopping the supplement.
One case involved a man who had taken 500 mg of ashwagandha extract for over a year without problems, then switched brands. Within 20 days of the new product, he developed jaundice and liver inflammation. This suggests that product quality, formulation, or contaminants may play a role alongside ashwagandha’s own compounds. If you have existing liver disease or take medications that stress the liver, the added burden from ashwagandha could be particularly risky.
Before Surgery
The American Society of Anesthesiologists and the American Association of Nurse Anesthetists recommend stopping all herbal supplements, including ashwagandha, one to two weeks before elective surgery. Ashwagandha’s sedative properties could interact unpredictably with anesthesia, and its effects on blood pressure and blood sugar add further complications in a surgical setting. If you have a procedure scheduled, let your anesthesia team know you’ve been taking it, even if you’ve already stopped.