Ashwagandha Side Effects: What to Know

For most healthy adults, ashwagandha’s side effects are mild: drowsiness, an upset stomach, and sometimes loose stools, usually easing at a lower dose or when taken with food. The effects worth taking seriously are uncommon but real, namely rare liver injury, a rise in thyroid activity, and immune stimulation. If you are pregnant, have a thyroid or autoimmune condition, or have liver trouble, ashwagandha is one to skip or clear with a clinician first. This is a your-money-or-your-life topic, so the cautions here are deliberate; our ashwagandha page and the stress guide set the ingredient in context.

Ashwagandha (Withania somnifera) is an adaptogenic herb used in Ayurvedic practice to support the body’s response to stress. It is generally well tolerated in short-term trials, which is why the mild effects dominate most people’s experience, but a responsible safety summary has to give the rare serious risks their due weight rather than burying them.

The common, mild effects

The effects most people actually meet are gentle and reversible. Drowsiness or a sedated, heavy feeling is the standout, which is part of why evening dosing is popular. Gastrointestinal upset comes next: nausea, loose stools, and stomach discomfort, more likely at higher doses and often better with food or a smaller amount. Some people report headache. A safety and effectiveness review by Tandon and Yadav (2020) found that across controlled trials ashwagandha’s adverse effects were mostly mild and transient, with drowsiness and digestive complaints the ones reported most. The US NCCIH overview of ashwagandha reaches the same practical view: usually well tolerated short term, with safety over longer periods less certain.

The rare but serious risks

These are the reasons a safety article exists. First, liver injury. A case series by Björnsson and colleagues (2020) described several previously healthy people who developed liver injury, with jaundice and raised liver enzymes, after taking ashwagandha, all of whom recovered after stopping. The NIH LiverTox database now lists ashwagandha as an established, if uncommon, cause of drug-induced liver injury. Stop and get medical care for yellowing skin or eyes, dark urine, severe tiredness, or pain under the right ribs.

Second, thyroid effects. Ashwagandha can raise T3 and T4, so it may push someone with an overactive thyroid, or on thyroid medication, out of range. Third, immune stimulation: because it can activate immune pathways, it may be unwise in autoimmune disease. None of these is common, but each changes who should take it.

Who should avoid it

Some groups should not take ashwagandha without medical guidance. Pregnant women should avoid it, as traditional use and safety concerns point to a miscarriage risk; caution applies in breastfeeding too. People with thyroid conditions or taking thyroid drugs risk shifting their hormone levels. People with autoimmune conditions such as lupus, rheumatoid arthritis, or Hashimoto’s should be cautious given the immune effect. People with liver disease, or already taking medicines that stress the liver, add risk on risk. Anyone facing surgery should stop beforehand because of the sedative effect, and it may add to sedatives, thyroid medication, and immunosuppressants.

What to look for in a safe ashwagandha supplement for daily use

If ashwagandha is right for you, the safety of the product itself comes down to a few label checks. First, choose a single-ingredient, root-only standardised extract such as KSM-66; root-only extracts have the longest safety record in trials, and a stated standardisation lets you match the studied dose. Second, keep to a studied dose, commonly around 300 to 600 mg a day, rather than mega-dose blends. Third, insist on third-party testing for identity, heavy metals, and contaminants, since adulteration is the avoidable risk here. Fourth, avoid products that stack other stimulants or sedatives, which muddy both effects and side effects. Our ashwagandha page walks through these checks so you can pick a product that matches what was actually researched, and the stress guide shows where it fits among other options.

Talk to your prescriber

Ashwagandha is a supplement that genuinely interacts with medication and with several health conditions, so the safe default is to treat it that way. If you take any prescription medicine, especially for the thyroid, blood pressure, blood sugar, or immune system, if you are pregnant or breastfeeding, or if you have a liver, thyroid, or autoimmune condition, speak to your doctor or pharmacist before starting and name every product you take. This article supports an informed conversation; it does not replace one.

This information supports, and does not replace, professional care. See our disclaimer and how to get help.