How long should it take for ashwagandha to be cleared from one's system? i tried one 650 mg capsule. i normally sleep reasonably well and it's apparently obliterated my ability to sleep, with terrible insomnia in my case?

Since supplements aren't investigated by the FDA we physicians do not have this information. Your pharmacist may have some information about this topic.

This is considered a herbal product so we likely do not have information about its half life. In general, most medications are cleared out of our system completely in 2 weeks. It is a surprise in your case because some people take this supplement for insomnia.