Who should not take ashwagandha?

Pregnancy. Some evidence suggests ashwagandha might cause miscarriages and should not be taken during pregnancy [1]. 

Breastfeeding. At this time, there is not enough research to determine whether ashwagandha is safe to use when breastfeeding.

Thyroid conditions. Ashwagandha can increase levels of thyroid hormones and should be taken with caution or avoided altogether if you have an overactive thyroid (hyperthyroidism) or if you take thyroid hormone medications [1]. Moreover, individuals with an overactive thyroid should not take ashwagandha as it can exacerbate hyperthyroidism. 

Autoimmune diseases. Ashwagandha can increase immune response, so it’s recommended that individuals with autoimmune diseases (such as multiple sclerosis, lupus, rheumatoid arthritis, type 1 diabetes, or other conditions) avoid taking ashwagandha [1].

Immunosuppressants. Since it can increase the activity of the immune system, taking ashwagandha and immunosuppressants simultaneously may reduce the effects of the medication.

Sedatives. Ashwagandha can increase sleepiness and slow breathing, so taking it alongside sedative medications (like Benzodiazepines or CNS depressants) may cause breathing problems and excessive sleepiness [1].

Diabetes drugs. Ashwagandha can lower blood sugar levels, so taking both ashwagandha and diabetes medications together may cause blood sugar to drop dangerously low. 

Blood pressure reducers. Ashwagandha can also lower blood pressure, so taking both ashwagandha and antihypertensive medications may cause blood pressure to drop too low.