Yes, we recommend fitting the Earthing sheet underneath your current bed sheet providing that any covering bed sheet is made from natural materials such as cotton or bamboo.
Some people prefer to fit the Earthing sheet as a top layer for more direct contact and to create a stronger connection. However, our multimeter tests have confirmed that a strong Earth connection is still achieved when the Earthing sheet is fitted underneath a cotton bed sheet, even with an additional layer of clothes/pyjamas before reaching the skin level.
In addition, as you lie on the covering sheet, perspiration and environmental humidity will hydrate your sheet which further strengthens the Earth connection.
You can test this yourself with a simple conductivity test which we are happy to recommend.