GlaxoSmithKline operates in three primary areas of business: Pharmaceuticals, Vaccines, and Consumer Healthcare. In 2014, 67.3% (£15.5 billion) of net turnover came from the Pharmaceuticals division, 13.9% (£3.2 billion) from Vaccines, and 18.8% (£4.3 billion) from Consumer Healthcare.

Within the Pharmaceutical division, key areas of focus include respiratory diseases, oncology, and cardiovascular disease. The company's largest selling product is the Advair Discus (also marketed under the trade name Seretide), with £4.2 billion in 2014 sales. Advair Discus is a co-formulation of the corticosteroid fluticasone propionate and the long-acting beta agonist salmeterol xinafoate.^[1] The product carries a "black box" warning stating that monotherapy with long acting beta agonists has been shown to increase mortality in people with asthma, that there is insufficient evidence to say whether this is also true for corticosteriod-long acting beta agonist combination products, and that Advair should only be used by people who cannot achieve satisfactory symptom relief with corticosteroids alone. Maintenance therapy with inhaled corticosteroids, which was pioneered by Glaxo with the development of beclomethasone in the early 1970's,Cite error: A <ref> tag is missing the closing </ref> (see the help page). A 2007 Cochrane review concluded that compared to beclomethasone or budenoside, fluticasone produced a significantly greater improvement in both morning and evening peak expiratory flow (PEF) and forced expiratory capacity (FEV1) but variable effects on acute exacerbations.^[2] The patents for both fluticasone and salmeterol have expired, but generic versions of Advair will not be available until 2016 because of Glaxo's patent on the delivery device.^[3]