Eating a nourishing, balanced diet is important to help keep us healthy, active and independent.

When you are unwell, or recovering from an operation or infection, it can sometimes be hard to eat well. You might not feel like eating, or you may be suffering from symptoms or side effects of your illness, treatment or medications, which can affect your appetite and ability to eat. All this can make it difficult to get enough of what your body needs to recover and so could lead you to becoming weaker and having less strength and energy than usual. It can also make you more likely to pick up an infection. You may find yourself losing weight, even if you are not trying to do so. Over time, if you do not have enough food to eat you may unintentionally lose weight and become malnourished. 

What are the main signs & symptoms of unintentional weight loss? 

Unintentional weight loss can lead to a reduced quantity of body fat and/or reduced muscle or bone strength. Healing times and your recovery period may be longer than expected. You may feel tired, have low energy levels or find it hard to keep warm. This in turn could also lead to other effects, such as reduced quality of life, digestive problems or your mood may be affected. Unintentional weight loss may also be referred to as malnutrition. 

Can you be overweight and malnourished? 

Yes, malnutrition is most commonly associated with weight loss, but it is possible to be overweight and malnourished. Often malnutrition is missed in overweight or obese people, or people may regard the weight loss as a positive side effect. However unintentional weight loss, no matter what weight you were initially, can lead to loss of muscle as opposed to loss of fat and so can lead to malnutrition and all the side effects mentioned above. 

Managing your diet when you have unintentionally lost weight 

The best way to manage malnutrition is to ensure that your diet contains a balanced mix of nutrients such as energy, protein, vitamins and minerals. However, if you have a poor appetite or are having problems eating due to illness, it can be difficult to obtain all these nutrients from your diet. 

What are Oral Nutritional Supplements, (ONS)? 

Oral Nutritional Supplements (ONS) are medical nutrition products that contain important nutrients such as energy, protein, vitamins and minerals that you would normally get from the food you eat. They are specially designed to help provide you with the nutrients your body needs, when you are unable to achieve this through diet alone, to help you to maintain your body weight, restore your energy levels and help with your recovery. 

Why have you been prescribed ONS 

Your healthcare professional, (HCP), may feel you could benefit from taking ONS, if they think you require extra nutrition to meet your energy and nutrient needs and you are not able to achieve this through diet alone. If you are unwell, or recovering from an illness, you may need more food than usual due to increased requirements or increased losses. However, your appetite might be poor, and you could struggle to eat and drink enough. If this is the case, your HCP may prescribe ONS to bridge this energy and nutrient gap. 

How many ONS do you need to take a day? 

ONS can help improve your dietary intake but it is important that you take them every day as recommended by your HCP. Your HCP will explain how many ONS you should take to meet your nutritional needs. It is important that you try to take the recommended amount each day, for the recommended length of time, to help you achieve your nutritional goals. If in doubt, you can check with your pharmacist that issued your prescription. 

When should you take your ONS? 

In general people take their ONS when they feel like drinking or eating them. This may be between meals as a snack, first thing in the morning, or before bedtime. Others find it easier to take small amounts regularly throughout the day but try to get into a regular routine and take your ONS at the same time each day. However, please always follow the advice given by your HCP. You should try to avoid using your ONS as a meal replacement, where possible. 

What happens if you forget to take it? 

In general, you can take your prescribed ONS whenever it’s most convenient for you. If you forget to take it at your normal time, try taking it before bedtime or first thing in the morning. It is important to try and take the recommended amount each day. Speak to your HCP if you are taking medications and have concerns. 

Do you still need to take your ONS if you manage to eat a meal? 

ONS contain energy, protein, vitamins and minerals, which can help boost your dietary intake. They are designed to be taken in addition to your normal meals, so it is important you take the prescribed amount each day between meals, like a snack. If you feel you no longer need them, you should seek the advice of your HCP before stopping your prescribed intake. 

How long should you expect to continue taking your ONS? 

Your HCP should review and monitor your progress and may agree goals you would like to achieve whilst taking ONS, such as maintaining or gaining weight, increasing energy levels or until you feel able to eat and drink enough to meet your nutritional requirements. They will also assess how long you need to continue taking your ONS. 

Oral nutritional supplements are Foods for Special Medical Purposes for the dietary management of disease related malnutrition and must be used under medical supervision. 


Malnutrition is most commonly associated with weight loss but there are other effects. 

  • More likely to pick up an infection. 
  • A delay in a recovery from an infection 
  • Loss of bone strength 
  • Digestive problems 
  • Micronutrient deficiency 
  • Mood changes 
  • Reduced quality of life 
  • Might take you longer to heal from injury 

What should you do if you can’t manage or don’t like the ONS you have been prescribed?  

If you are struggling to consume the amount you have been prescribed or are not keen on the flavour you have received, speak to your HCP. There are lots of different styles and flavours of ONS available. Styles include milkshake, juice, yoghurt and dessert style. There is also a wide variety of flavours and volumes. Ask them about trying new flavours or varieties and ask if there is a starter pack available so you can try a variety of flavours.  

Can I use them in cooking?

Yes, ONS can be used in recipes and there are some special recipes books available. For a copy either call the Nutricia Patient and Carer Helpline numbers below or go to  

Can I heat them? 

Yes, you can gently warm your ONS especially if you want to add certain flavours to soups, hot drinks, or custard. However, do not boil them as you risk destroying some of the nutrients. 

Can I freeze them?  

Yes, pour the ONS into a freezer-safe container, ice cube tray or ice lolly mould, and freeze. These make a refreshing snack for hot weather or may help to relieve a sore mouth. If you would like some hints and tips, or recipe ideas, to help you take your ONS, visit or speak to your HCP. 

What should you do if you start to lose weight unexpectedly, or have a poor appetite when you stop taking ONS? 

If you notice changes in your appetite, weight or are unable to eat enough food, discuss your concerns with your HCP as soon as possible. If you have seen a dietitian and they have given you any information, you should take this with you when you next visit your GP. Your chosen pharmacy will be able to dispense your prescribed oral nutritional supplements. 

This article is intended to help patients who have been prescribed oral nutritional supplements. 

Pharmacy2U By Pharmacy2U Published 10/12/2020