Ashwagandha can interact with several categories of medications and is unsafe for certain health conditions. The most important ones to know about are thyroid medications, diabetes drugs, sedatives, immunosuppressants, and blood pressure medications. Beyond drug interactions, ashwagandha is also contraindicated during pregnancy, before surgery, and for people with autoimmune diseases or serious liver problems.
Thyroid Medications
Ashwagandha directly stimulates the thyroid gland to produce and release more thyroid hormone. Animal studies show it can increase circulating levels of the primary thyroid hormone (T4) by roughly 111%. This means combining it with thyroid replacement medications like levothyroxine can push hormone levels dangerously high, a condition called thyrotoxicosis. One documented case involved a woman with hypothyroidism who replaced her levothyroxine with ashwagandha and developed a dangerously fast heart rhythm from excess thyroid hormone.
If you have any thyroid condition, whether overactive or underactive, ashwagandha is risky. For people with hypothyroidism on medication, it can cause hormone levels to overshoot. For people with hyperthyroidism, it can make an already overactive thyroid worse.
Diabetes and Blood Sugar Medications
Ashwagandha lowers blood sugar by increasing glucose uptake into muscle and fat cells and by boosting insulin secretion. If you’re taking insulin or oral diabetes medications, adding ashwagandha on top can drop your blood sugar too low. This interaction is classified as moderate, meaning it won’t necessarily cause problems for everyone, but the risk of hypoglycemia is real enough to warrant caution. People who are malnourished, elderly, or have nerve damage affecting their body’s ability to recognize low blood sugar are especially vulnerable.
Sedatives and Anti-Anxiety Drugs
Ashwagandha has sedative properties that can amplify the effects of medications in the same category. The National Institutes of Health notes preliminary evidence that it may increase the effects of benzodiazepines like diazepam (Valium) and alprazolam (Xanax), along with other sedatives and anti-anxiety drugs. The concern is compounded drowsiness, slowed breathing, and impaired coordination. This extends to barbiturates, sleep medications, and muscle relaxants. If you take anything prescribed specifically to calm your nervous system or help you sleep, combining it with ashwagandha can intensify those effects beyond what your doctor intended.
Blood Pressure Medications
Ashwagandha can affect blood pressure, though the interaction isn’t always predictable. In at least one clinical study, patients already taking blood pressure-lowering drugs experienced an unexpected increase in blood pressure while using ashwagandha. Because ashwagandha can shift blood pressure in either direction depending on the individual, combining it with antihypertensive medications makes your blood pressure harder to manage and monitor reliably.
Immunosuppressants
Ashwagandha stimulates immune activity, which is the opposite of what immunosuppressive drugs are designed to do. For people taking corticosteroids or calcineurin inhibitors after an organ transplant, ashwagandha can reduce the effectiveness of those medications. That’s a potentially life-threatening interaction, since weakened immunosuppression can trigger organ rejection. The same principle applies to anyone on immunosuppressive therapy for any reason.
Autoimmune Conditions
Even without a drug interaction, ashwagandha is a problem for people with autoimmune diseases. Its immune-boosting properties can worsen conditions where the immune system is already attacking the body’s own tissues. Specifically, it can provoke flares in lupus, rheumatoid arthritis, multiple sclerosis, and dermatomyositis. Ashwagandha, along with other immunostimulatory herbs like echinacea and elderberry, poses real risks to anyone managing an autoimmune condition.
Pregnancy and Breastfeeding
The NIH states plainly that ashwagandha should be avoided during pregnancy and should not be used while breastfeeding. Animal data suggest it may have properties that could induce miscarriage, and there isn’t enough human safety data to consider it safe for either situation.
Liver Disease
Ashwagandha has been linked to rare but serious liver injury. A review of the medical literature identified 23 reported cases of liver damage attributed to the supplement, typically appearing as a type of liver inflammation about a month after starting use. Most cases resolved on their own after stopping the supplement, but there have been rare instances of fatal liver failure and cases requiring emergency liver transplantation, particularly in people with preexisting liver disease.
If you have cirrhosis or advanced chronic liver disease, ashwagandha should be avoided entirely. For people with healthy livers, the overall risk is low (ashwagandha accounted for roughly 1% of all herb-related liver injury cases in one large review), but it’s worth being aware of. The compounds suspected of causing liver toxicity are called withanolides, though the exact mechanism remains unclear.
Before Surgery
The American Society of Anesthesiologists recommends stopping all herbal supplements at least two weeks before any scheduled surgery. Ashwagandha’s sedative effects can interact unpredictably with anesthesia, and it may also affect bleeding risk. If you have a procedure coming up, stop taking ashwagandha 14 days in advance and let your surgical team know you’ve been using it.