Hi, Ranitidine or Zantac is used to treat gastric acidity and heartburn. There are reports and studies that cause insomnia but the mechanism is not precisely known. It works by blocking histamine receptors which are involved in the acid release. The possibility is there but least and occurs mostly in elders. In order to avoid such symptoms take it in the morning time. But I feel there may be other predisposing factors in your case like: - Night work. - Sleeping in the day. - Use of mobile phones before sleep or in bed. - Use of tea or coffee in evening hours. You are suggested to assess yourself and adjust accordingly. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Soheel Hussain Zargar, Dentist