Oral Nutritional Supplements (ONS)

Oral Nutritional Supplements (ONS) are sterile liquids, semi-solids or powders, which provide macro and micro nutrients. They are widely used within the acute and community health settings for individuals who are unable to meet their nutritional requirements through oral diet alone. ONS use must be approved by the Advisory Committee on Borderline Substances (ACBS). Indications for use include:

  • Short bowel syndrome
  • Dysphagia
  • Intractable malabsorption
  • Pre-operative preparation of undernourished patients
  • Inflammatory bowel disease
  • Total gastrectomy
  • Bowel fistulae
  • Disease related malnutrition (chronic/acute)

ONS may be prescribed in the short term during acute illness, but also for individuals with long term chronic conditions. The role of ONS is to complement nutritional intake, and simultaneous information around improving oral intake should be provided.

Some ONS are available to buy over the counter in supermarkets or pharmacies (usually in powder form which are mixed with milk or water) but the majority of ONS are only available on prescription ideally following advice from a registered dietitian. ONS often contain macronutrients (protein and/or energy) and micronutrients (vitamins and minerals) at varying levels of concentrations. Therefore, not all ONS are nutritionally complete, meaning that they cannot be used as a sole source of nutrition. Individual dietetic assessment will take into account nutritional requirements and taste and texture preferences to ensure a tailored prescription is advised.

The following table shows the most common types of ONS available:

Juice typeVolume ranges from 200-220ml with an energy density of 1.25-1.5kcal/ml. They are fat free
Milkshake typeVolume ranges from 125-220ml, energy density ranges from 1-2.4kcal/ml. Also available with added fibre.
High-energy powdersVolume ranges from ~125-350ml, ideally made up with full cream milk to give an energy density of 1.5-2.5kcal/ml.
Soup typeVolume ranges from 200-330ml. Some are ready mixed and others are a powder and can be made up with water or milk to give an energy density of 1–1.5kcal/ml.
Semi-solid/dysphagia rangesRange of presentations from thickened liquids (stage 1 and 2) to smooth pudding styles (stage 3), with an energy density of ~1.4-2.5kcal/ml.
High proteinRange of presentations; jellies, shots, milkshake style containing 11-20g of protein in volumes ranging from 30–220ml.
Low volume high concentration (shots)These are fat and protein based products that are taken in small quantities (shots), typically 30-40ml as a dose taken 3-4 times daily.

What else should be considered?

  • Further information regarding suitability of ONS should be checked with individual manufacturers for example, gluten or lactose free, halal or kosher.
  • ONS should be used with caution in those with dysphagia to ensure the correct consistency is provided. Thickeners can be added to obtained the recommended consistency.
  • A range of flavours should be offered to avoid taste fatigue.
  • There is an emerging group of ONS which are designed for individuals over the age of 65 years who can be at risk of vitamin D deficiency.
  • Other products may be useful in patients with specific medical conditions where fluid and electrolyte balance is important. Patients with short gut may not tolerate heyperosmolar ONS as they may increase stoma losses.


ONS should not be prescribed without being monitored to ensure that they remain appropriate and are being taken as prescribed. ONS may be stopped when:

  • Dietary intake is meeting nutritional requirements.
  • Weight has increased to target.
  • BMI is within healthy range.
  • The individual’s medical condition has changed, e.g. an individual with a swallowing difficulty recovers some/all of their functionality.
  • The individual can no longer tolerate them due to taste fatigue.