Fortisip Compact Fibre Vanilla 4x125ml. Fortisip Compact Fibre is a Food for Special Medical Purposes for use under medical supervision. Fortisip Compact Fibre is a high energy (2.4kcal/ml), ready to drink, milkshake style nutritional supplement, containing 4.5g fibre per bottle, for the dietary management of disease related malnutrition.. Fortisip Compact Fibre can be used to supplement the diet of patients unable to meet their nutritional requirements from other foods.