Ashwagandha is generally well tolerated in the short term, but it can cause digestive discomfort, drowsiness, and thyroid changes. In rare cases, it has been linked to serious liver injury. Most clinical trials have only tracked safety for about three months, so the risks of long-term use remain unclear.
Digestive Side Effects
The most commonly reported side effects of ashwagandha are gastrointestinal: nausea, diarrhea, vomiting, and general stomach upset. These tend to be mild and are more likely when taking ashwagandha on an empty stomach or at higher doses. Taking it with food often reduces the discomfort.
Drowsiness and Sedation
Ashwagandha has calming properties, which is part of why people take it for stress and sleep. But that same effect can tip into unwanted daytime drowsiness. The herb influences receptors in the brain involved in relaxation and sleep regulation, and a compound found in ashwagandha leaves (triethylene glycol) may actively promote sleepiness.
This becomes a bigger concern if you’re also taking anything else with sedative effects. Ashwagandha can amplify the effects of anti-anxiety medications, sleep aids, muscle relaxants, barbiturates, and benzodiazepines. That combination can lead to excessive drowsiness, impaired coordination, muscle weakness, headaches, reduced libido, and muscle tremors.
Thyroid Hormone Changes
Ashwagandha appears to directly stimulate the thyroid gland, increasing production of the hormones T3 and T4. For people with an underactive thyroid, this is sometimes seen as a benefit. But if your thyroid is already functioning normally or is overactive, the effect can push hormone levels too high.
In people with hyperthyroidism or Graves’ disease, ashwagandha can worsen symptoms like irritability, restlessness, nervousness, hand tremors, heart palpitations, and anxiety. If you take thyroid medication, ashwagandha may also interfere with your dosing, since it’s independently shifting the same hormones your medication is trying to regulate.
Liver Injury
Rare but serious cases of liver damage have been reported with ashwagandha use. In one published case, a patient was hospitalized with jaundice after taking ashwagandha supplements. They experienced itching, fatigue, digestive problems, and pale stools, with lab results showing sharply elevated liver enzymes and bilirubin, indicating acute hepatitis. Recovery required 3.5 months of intensive treatment after stopping the supplement.
Other documented cases followed a similar pattern: jaundice, elevated liver enzymes, and a diagnosis of drug-induced liver injury. In one case series, full recovery took up to eight months after discontinuation. In another, a patient’s liver values initially improved after stopping ashwagandha but then worsened again a week later before eventually resolving. The German Federal Institute for Risk Assessment specifically recommends that people with acute or pre-existing liver disease avoid ashwagandha supplements entirely.
Blood Sugar Effects
Ashwagandha can lower blood glucose levels. Lab studies suggest it works by increasing glucose uptake in muscle and fat cells and boosting insulin secretion. Some clinical studies in people with diabetes have confirmed reductions in blood sugar and HbA1c (a marker of long-term blood sugar control), though results have been inconsistent across trials.
If you take insulin or other diabetes medications, this blood sugar-lowering effect can stack on top of your medication and increase the risk of hypoglycemia, where blood sugar drops too low. Symptoms of hypoglycemia include shakiness, confusion, sweating, and dizziness.
Immune System Stimulation
Ashwagandha has immune-boosting properties, which sounds positive but creates a real risk for certain people. If you have an autoimmune condition like lupus, multiple sclerosis, or rheumatoid arthritis, your immune system is already overactive and attacking your own tissues. Stimulating it further can worsen flares and symptoms. For the same reason, ashwagandha can interfere with immunosuppressant medications, potentially reducing their effectiveness at a time when immune suppression is medically necessary.
Pregnancy and Breastfeeding
Ashwagandha has historically been used as an abortifacient, a substance intended to induce miscarriage. While modern clinical data on its effects during pregnancy is lacking, that traditional use raised enough concern that safety agencies have issued warnings. The German Federal Institute for Risk Assessment recommends that pregnant women, breastfeeding mothers, and children avoid ashwagandha supplements, citing insufficient safety data for these groups.
Other Drug Interactions
Beyond the interactions already mentioned, the NIH notes that ashwagandha may interact with medications for high blood pressure (potentially causing blood pressure to drop too low) and anti-seizure medications. The pattern across these interactions is consistent: ashwagandha tends to amplify effects that overlap with what a medication is already doing, whether that’s lowering blood sugar, reducing blood pressure, calming the nervous system, or altering thyroid function.
Dosage and Duration Limits
A joint international taskforce recommended 300 to 600 mg per day of a standardized root extract for anxiety, though they noted more research is needed to strengthen that recommendation. One of the challenges with ashwagandha dosing is that supplements vary widely in how they’re prepared, extracted, and standardized, making it difficult to compare one product to another or to establish firm upper limits.
What is clear is that safety data beyond three months is sparse. Most clinical trials have lasted 8 to 12 weeks. A 12-month safety trial is currently underway, tracking 200 adults across multiple sites, but results are not yet available. Until that and similar studies report findings, the long-term safety profile of ashwagandha remains an open question. Taking it continuously for months or years means operating outside the window where researchers have closely monitored for problems.