Malnutrition means "poor nutrition" which can be caused by undernutrition or overnutrition.

The term is most commonly used to describe undernutrition, which is the focus here. Please see obesity for more information about overnutrition.

A balanced diet should provide enough nutrients such as calories, protein and vitamins, to keep you healthy. Without this, you may not be getting all the nutrients you need and this can lead to malnutrition.

Malnutrition can result in unplanned weight loss, a low body mass index (BMI) and vitamin and mineral deficiencies. This can leave you feeling tired, weak and affect your ability to recover from an illness.

In the UK, evidence suggests that:

  • 29% of people admitted to hospital are malnourished
  • 35% of people admitted to care homes are malnourished
  • 12% of people aged 65 and over, living at home in the community are malnourished

Conditions that can cause malnutrition

Certain medical conditions can cause increased requirements or lead to your body being unable to absorb or use nutrients properly. These may include:

  • cancer and liver disease that can cause a lack of appetite, persistent pain or nausea
  • COPD, pulmonary fibrosis and emphysema, which can increase your calorie requirements and reduce your appetite
  • mental health illness, such as depression or schizophrenia, which may affect your ability to look after yourself
  • Crohn's disease, ulcerative colitis or cystic fibrosis that disrupt your body’s ability to digest food or absorb nutrients
  • burns, fractures and post major surgery, due to increased demand for nutrients
  • dementia – people with dementia may be unable to communicate their needs when it comes to eating, may use up a lot of calories pacing or may experience a loss of appetite
  • dysphagia – a condition that makes swallowing difficult or painful and can mean that only certain consistencies of foods and drinks (known as International Dysphagia Diet Standardisation Initiative levels) can be taken
  • persistent vomiting or diarrhoea

Sometimes taking multiple medications or certain types of medication may also increase your risk of developing malnutrition. Always check your medicines information and speak to your prescriber for advice if you have a concern. Do not stop taking your medication without advice from a health care professional.

Other causes of malnutrition

Malnutrition can also be caused by physical issues, social issues and ageing.

Physical issues

Physical issues can also contribute to malnutrition. For example:

  • if your teeth are in a poor condition, if your dentures do not fit properly, or if you have a sore mouth, eating can be difficult or painful
  • you may lose your appetite as a result of losing your sense of smell and taste
  • you may have a physical disability or other impairment that makes it difficult for you to cook or shop for food yourself.

Social factors

Social issues that can contribute to malnutrition include:

  • living alone and being socially isolated
  • having limited knowledge about nutrition or cooking
  • reduced mobility
  • alcohol or drug use
  • low income or poverty
  • reliance on food banks


Older adults are particularly vulnerable to malnutrition because of physical, psychological and social factors, and because the risk of having one or more medical conditions is higher.

Signs and Symptoms of Malnutrition

Malnutrition can be difficult to recognise and can happen very gradually, which can make it very difficult to spot in the early stages.

Common signs and symptoms to watch out for include:

  • loss of appetite and lack of interest in food and/or fluids
  • unplanned weight loss – clothing, rings, watches or dentures may become loose
  • tiredness or low energy levels
  • reduced ability to perform everyday tasks – for example, showering, getting dressed or cooking
  • reduced muscle strength – for example, not being able to walk as far or as fast as usual
  • changes in mood – malnutrition can be associated with lethargy and depression
  • poor concentration
  • poor growth in children
  • increased risk of infection, recurrent infections, taking longer to recover and poor wound healing
  • difficulty keeping warm
  • dizziness

Non-urgent advice: When to see your GP

You should see your GP if you have had any of the above symptoms and have noticed a drop in weight or lost weight without trying.

Diagnosing malnutrition

A health care professional can assess you for malnutrition using a screening tool such as ‘Malnutrition Universal Screening Tool’ (‘MUST’). This tool assesses individuals as being at low, medium or high risk of malnutrition.

Screen yourself for malnutrition

Treating malnutrition

If you have lost weight or your appetite is poor, making simple changes to your meals, snacks and drinks may help.

Choosing nutrient-dense food and drinks can help improve your calorie intake without having to make the portion size much bigger. This advice may not be suitable for everyone, especially those with other conditions such as diabetes or swallowing difficulties.

Ask your doctor, dietitian or nurse for further advice if you are unsure.

If you have previously required to limit the fat and sugar in your diet due to health concerns e.g. high cholesterol or diabetes, you may wish to talk to a health professional.

The following ideas will help you to increase the amount of calories and protein in your diet:

  • Eat ‘little and often’ – 3 small meals a day with 2-3 snacks in-between meals
  • Include protein at each meal such as meat, fish, chicken, eggs, beans or lentils
  • Avoid low fat, sugar-free, diet foods and drinks for example skimmed milk
  • Add high calorie ingredients to meals and drinks including full cream milk, cheese, butter, olive oil and cream
  • Try not to have drinks just before meals to prevent you from feeling full
  • Include puddings after your lunch and evening meal such as creamy yoghurts, custards, rice pudding, milk puddings or ice-cream
  • Try ready meals if you don’t feel like cooking
  • Try including 1 pint of full cream milk each day - this can be enriched by adding 4 tablespoons of dried milk powder. Use this instead of milk and water in drinks, cooking, cereals and puddings
  • Choose nourishing drinks such as milky drinks (malted drinks, hot chocolate, milky coffee and milkshakes) or high sugar drinks such as fruit juice, smoothies, fizzy drinks or squash

Ideas for adding high-calorie ingredients to food and drinks are outlined in the table.

Add extra cheese or flavoured soft cheese to: Add extra butter to: Add sugar, jam or honey to: Add cream, chocolate spread, peanut butter or nuts to:
Sauces (aim for creamy sauces) Sandwiches or toast Puddings Porridge
Pasta dishes or pizza Mashed potatoes Hot drinks Fruit
Soups Vegetables Milkshakes or smoothies Sauces
Scrambled eggs or omelettes Sauces Glazed vegetables Soups
Mashed potatoes Baked potatoes Creamy yogurts Smoothies or milkshakes
Vegetables Snacks (pancakes, crumpets, scones) Fruit Snacks (toast, pancakes, crumpets, scones, waffles, rice cakes)
Beans on toast Biscuits or cracker Porridge or cereal Ice-cream or puddings

Ideas for high calorie and protein snacks include:

  • crackers or oatcakes with cheese, pate, hummus or avocado
  • crumpets, scones and pancakes with butter and jam
  • thick and creamy yoghurts
  • soya yoghurts or desserts
  • milk jelly, chocolate pots and mousses
  • custard, trifle and rice pudding pots
  • dried fruit
  • nuts and seeds
  • cereal bar and flapjacks
  • mini pork pie, sausage roll, scotch egg and spring rolls
  • chocolate, biscuits, pastries and cakes
  • crisps with dip
  • fruit with chocolate spread or peanut butter

The British Dietetic Association (BDA) Malnutrition factsheet provides more useful practical advice.

Oral Nutritional Supplements

Oral nutritional supplements (often shortened to ONS) are a range of liquid and powder products that can be recommended, within certain circumstances, to help support better nutrition.

These products contain calories, protein, vitamins and minerals to help increase your intake. They are designed to be taken alongside your diet and the ‘food first’ advice above to promote progress with your weight.

Depending on your medical background you may have them prescribed by a dietitian or doctor, however, you can buy some products in chemists and supermarkets, such as Meritene® and Complan®. It is illegal to use or share products prescribed for another person.

These products do not contain all the nutrition you need and so are not designed to replace food but complement what you can manage.

A dietitian will usually assess your medical history, your nutritional needs and taste likes and dislikes before advising you on a product.

ONS is clinically proven to be most helpful in a course of up to 12 weeks. Regular review is important, by the prescriber, to make sure the product is helping you in the right way and helping you meet your treatment goals.

Tube feeding (enteral feeding)

In certain situations, hospital admission may be required. A full assessment will be carried out by all or some of the following people:

  • Doctor
  • Dietitian
  • Specialist Nurse
  • Pharmacist

It may be considered necessary due to symptoms that you are experiencing to have what we call a “feeding tube” placed.

There are several types of tubes and the choice is dependent on your diagnosis and symptoms. These include:

  • Nasogastric – through your nose and into your stomach
  • Nasojejunal – though your nose and further into your digestive tract
  • Percutaneous Endoscopic gastrostomy (PEG) - a tube is placed directly into the stomach via your abdomen

There are various other tubes but these are the most common types.

On occasions, depending on your condition, alternative routes of nutrition may be considered.

Time spent in hospital will depend on your condition and the cause of poor nutrition. In many cases, it is possible to return home while still receiving treatment to improve your nutritional state.


Source: SDPSG TEC Subgroup

Last updated:
17 May 2021

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