The FMCG giant is understood to have invited digital agencies to submit their details to an online portal to take part in a survey as part of the roster review.
However, it has not provided any further details about which territories the review will include.
GSK specialises in consumer healthcare and the nutritional healthcare business, with brands including Ribena, Lucozade and Aquafresh.
It has highlighted consumer healthcare as a key driver for growth and is selling off 19 brands, including Nytol and FiberChoice, from that part of the business to focus on oral health and nutrition categories, which include Sensodyne, Panadol and Horlicks.
GSK recently rolled out the biggest campaign to date for its dental healthcare brand Corsodyl, created by Grey and valued at £7.3 million.
GSK did not respond to a request for comment.