The drink comprises carbonated water, lemon fruit from concentrate (2%), citric acid (acid), acidity regulator (sodium citrate), sweeteners (aspartame, sodium saccharin), antioxidant (ascorbic acid), preservative (potassium sorbate), natural flavourings including quinine, stabilisers (modified starch, glycerol esters of wood rosins), and colours (copper complexes of chlorophyllins, carotenes). ​

Schweppes Slimline Bitter Lemon 6 x 1ltr is free from the 14 major allergens, including gluten, dairy, nuts, soy, and sulphites, making it suitable for individuals with common food allergies. It is also gluten-free, GMO-free, and suitable for vegetarians and vegans. However, it contains aspartame, a source of phenylalanine, which may be unsuitable for individuals with phenylketonuria (PKU).