A brief has been sent out to network agencies and creative hotshops.
The move is understood to be procurement-led and has not been instigated by GSK's marketing department.
The company's UK business is worth around £30 million and is handled by a roster of agencies including M&C Saatchi, Ogilvy & Mather, Grey London and WCRS.
M&C handles most of GSK's drinks range, including Lucozade Sport and Ribena.
Grey looks after the majority of the company's healthcare range, as well as its oral hygiene brands Sensodyne and Aquafresh.
Ogilvy & Mather handles GSK's pharmaceutical and chemical brands including Panadol, Zovirax and the Lucozade Energy drinks.
The review is not thought to affect the company's media planning and buying business, handled by MediaCom.