It is impossible for your healthcare provider to know whether you will develop insomnia while taking Evista. Also, in some cases, if a person does develop insomnia, it is difficult to know whether these problems are due to Evista or other factors. If you develop insomnia while taking the drug, make sure to talk with your healthcare provider. He or she may be able to recommend other treatments, including adjusting the Evista dosage or trying another medication.