The most common side effects of supplementing with ashwagandha - and who should avoid this medicinal herb

• Ashwagandha's side effects include upset stomach, nausea, and drowsiness.
• Because of ashwagandha's side effects, avoid it if you are pregnant or have an autoimmune disorder.
• To minimize side effects, only take ashwagandha for a maximum of three months.

Ashwagandha, an herb used in traditional Indian medicine, is typically used to help the body manage and adjust to stress. Modern studies found it may also boost cognitive function and memory, increase muscle strength, and improve infertility in men.

Rare but serious complications of using ashwagandha include liver injury, rapid heartbeat, and allergic reactions. However, common side effects are typically mild and resolve when you stop using the herb.

Typical doses are between:

• 1,000 milligrams (mg) to 6,000 mg of root powder
• 500 mg to 1500 mg of root extract

Important: Ashwagandha is less likely to cause severe complications if you stop using it after three months, says Nicole M. Avena, an assistant professor of neuroscience at Mount Sinai School of Medicine.

If you're interested in taking ashwagandha, here are the potential side effects you should know about.

1. Nausea, stomach upset, diarrhea

Uncomfortable gastrointestinal symptoms like nausea, upset stomach, and diarrhea are the most common side effects of ashwagandha.

"Large doses of ashwagandha [more than 6,000 mg of root powder or 1500 mg of root extract] can cause irritation of the membranes inside the stomach," says Khara Jefferson, DNP, APRN, owner of KAJ Wellness Professionals, LLC.

These side effects are typically tolerable and will resolve when you stop taking ashwagandha.

Important: See a doctor if you can't keep food or water down, are experiencing severe abdominal pain, or symptoms don't resolve once you stop taking the supplements, Avena says.

2. Drowsiness

While studies found ashwagandha may help you sleep better at night, drowsiness can be an unwelcome side effect for some users, interrupting day-to-day tasks and making it dangerous to operate a vehicle.

Johnson says ashwagandha's sedative effects are likely more noticeable in people who are taking other sedative drugs, like benzodiazepines and barbiturates.

Who should not take ashwagandha

"Ideally everyone should consult with their doctor before taking any supplements," Avena says, but it's especially important for certain people to talk with a healthcare professional before use, or to avoid ashwagandha altogether.

You should avoid ashwagandha altogether if:

• You are pregnant: "Ashwagandha is generally regarded as unsafe in pregnancy because it has abortifacient effects," meaning it can induce abortions, Jefferson says. "The compounds in it can cause miscarriage, premature birth, or even uterine contractions."
• You have a thyroid condition or take thyroid medication: Ashwagandha has been shown to alter thyroid function and increase thyroid hormones, which could be dangerous for people with hyperthyroidism. "It could also potentially interfere with thyroid tests, so it's always important to let your doctor know if you are taking ashwagandha," Avena says.
• You have hormone-sensitive prostate cancer: Ashwagandha can increase testosterone levels which could be dangerous for patients with prostate cancer.
• You take benzodiazepines, anticonvulsants, or barbiturates: Ashwagandha might increase drowsiness, particularly in people taking certain medications.
• You have an autoimmune condition: Ashwagandha is immunostimulating, which means it boosts the immune system. Immunosuppressant drugs are prescribed to people with autoimmune conditions to help suppress the body's immune system and taking ashwagandha could decrease the effects of these drugs, Johnson says.

You should consult with a doctor before taking ashwagandha if you:

• Have diabetes: Ashwagandha has been shown to decrease blood sugar levels in animal studies. It's not clear if this is applicable to humans, therefore, people with diabetes should consult with their doctor before taking ashwagandha.
• Have stomach ulcers: People with stomach ulcers should talk to a doctor before taking ashwagandha as it can irritate the lining of your gastrointestinal tract exacerbating the ulcers, Johnson says.

Important: If you're preparing to have surgery that requires anesthesia, be sure to stop taking ashwagandha two weeks ahead of time to avoid a potential drug interaction with the anesthesia, Johnson says.

Insider's takeaway

Ashwagandha has been used for thousands of years and is generally considered safe. But some users report experiencing mild side effects like upset stomach, nausea, diarrhea, and drowsiness.

Because herbal supplements are not FDA regulated, opt for a brand that has been third-party tested. A product is third-party tested if it displays the third-party tested label.