These are supplements, usually ready-made drinks or powders that can be added to milk to make a drink that will replace meals for those who are unable to eat. Some products are also available in the form of soups. This type of supplement aims to supply all known nutrients for those who cannot eat any food at all, but if consumed in this way there are high-protein drinks. If people cannot eat food for more than a day or two advice should be sought form a medical practitioner, who may refer the person to a dietitian.
Other supplements may be available on prescription for people with particular conditions; these are usually prescribed by a doctor on the advice of a dietitian, but may also sometimes be sold over the counter. They may be milk based or fruit based and are ready-made. They do not necessarily supply the whole range of nutrients and may therefore not be suitable for people who cannot eat solid food at all.