Malnutrition is a serious condition that happens when your diet does not contain the right amount of nutrients.

It means "poor nutrition" and can refer to:

  • undernutrition – not getting enough nutrients
  • overnutrition – getting more nutrients than needed

This topic focuses on undernutrition in adults and children. Read about obesity for more about the problems associated with overnutrition.

Signs and symptoms of malnutrition

Common signs of malnutrition include:

  • unintentional weight loss – losing 5 to 10% or more of weight over 3 to 6 months is one of the main signs of malnutrition
  • a low body weight – people with a body mass index (BMI) under 18.5 are at risk of being malnourished (use the BMI calculator to work out your BMI)
  • a lack of interest in eating and drinking
  • feeling tired all the time
  • feeling weaker 
  • getting ill often and taking a long time to recover
  • in children, not growing at the expected rate or not putting on weight as would normally be expected

When to see a GP

See a GP if:

  • you've unintentionally lost a lot of weight over the last 3 to 6  months
  • you have other symptoms of malnutrition
  • you're worried someone in your care, such as a child or older person, may be malnourished

If you're concerned about a friend or another family member, try to encourage them to see a GP.

A GP can check if you're at risk of malnutrition by measuring your weight and height and asking about any medical problems you have, or any recent changes in your weight or appetite.

If they think you could be malnourished, they may refer you to a healthcare professional such as a dietitian to discuss treatment.

Who's at risk of malnutrition

Malnutrition is a common problem, affecting millions of people in the UK.

Anyone can become malnourished, but it's more common in people who:

People who are 65 years and over are particularly at risk, and weight loss is not an inevitable result of old age. Children under the age of five are also at risk.

Treatments for malnutrition

Treatment for malnutrition depends on your general health and how severely malnourished you are.

The first dietary advice is usually to:

  • eat "fortified" foods that are high in calories and protein
  • snack between meals
  • have drinks that contain lots of calories 

Some people also need support to help with underlying issues such as limited mobility – for example, care at home or occupational therapy.

If a child is malnourished, their family may need advice and support to address the underlying reasons why it happened.

If these initial dietary changes are not enough, a doctor, nurse or dietitian may also suggest you take extra nutrients in the form of nutritional drinks or supplements.

If you have difficulty eating and this cannot be managed by making changes such as eating soft or liquid foods, other treatments may be recommended, such as:

  • a feeding tube – this can be either passed down the nose and into your stomach, or inserted directly into your stomach through the skin of the tummy
  • nutrition that's given directly into a vein

Preventing malnutrition

The best way to prevent malnutrition is to eat a healthy, balanced diet.

You need to eat a variety of foods from the main food groups, including:

  • plenty of fruit and vegetables
  • plenty of starchy foods such as bread, rice, potatoes, pasta
  • some milk and dairy foods or non-dairy alternatives
  • some sources of protein, such as meat, fish, eggs and beans

The Eatwell Guide has more information about the types of food you should include in your diet and how to get the right balance between them all.

Speak to a GP or specialist if you have a health problem that puts you at increased risk of malnutrition. You may have more complex dietary needs or need to take supplements.


The main symptom of malnutrition (undernutrition) is unintended weight loss, although this is not always obvious.

Weight loss

Most people who are malnourished will lose weight, but it is possible to be a healthy weight or even overweight and still be malnourished.

For example, this can happen if you're not getting enough nutrients, such as some types of vitamins and minerals, through your diet.

You could be malnourished if:

  • you unintentionally lose 5 to 10% of your body weight within 3 to 6 months
  • your body mass index (BMI) is under 18.5 (although a person with a BMI under 20 could also be at risk) – use the BMI calculator to work out your BMI
  • clothes, belts and jewellery seem to become looser over time

See a GP if you've unintentionally lost a lot of weight over the last few months.

If a friend or family member has lost lots of weight, talk to them about your concerns and encourage them to get help.

Other symptoms

Other signs of malnutrition include:

  • reduced appetite
  • lack of interest in food and drinks
  • feeling tired all the time
  • feeling weaker 
  • getting ill often and taking a long time to recover
  • wounds taking a long time to heal
  • poor concentration
  • feeling cold most of the time
  • low mood, sadness or depression

See a GP if you have these symptoms. If you notice these problems in someone else, try to encourage them to get help.

Symptoms in children

Symptoms of malnutrition in a child can include:

  • not growing or putting on weight at the expected rate (faltering growth)
  • changes in behaviour, such as being unusually irritable, slow or anxious
  • low energy levels and tiring more easily than other children

See a GP if you're concerned about your child's health or development at any point.

Who can get it

Malnutrition (undernutrition) is caused by a lack of nutrients, either as a result of a poor diet or problems absorbing nutrients from food.

Certain things can increase your risk of becoming malnourished.

Health conditions

Some health conditions that can lead to malnutrition include:

You can also become malnourished if your body needs an increased amount of energy – for example, if it's healing after surgery or a serious injury such as a burn, or if you have involuntary movements such as a tremor or shaking hands.


Some types of medication may increase your risk of developing malnutrition.

Some medicines have unpleasant side effects – such as making you feel sick, loss of appetite, or having diarrhoea, which could mean you eat less or don't absorb as many nutrients from your food.

Physical and social factors

The following factors can also contribute to malnutrition:

  • teeth that are in a poor condition, or dentures that don't fit properly, which can make eating difficult or painful 
  • a physical disability or other impairment that makes it difficult to move around, cook or shop for food
  • living alone and being socially isolated
  • having limited knowledge about nutrition or cooking
  • alcohol or drug dependency
  • low income or poverty

Causes of malnutrition in children

In the UK, malnutrition in children is commonly caused by long-term health conditions that:

  • cause lack of appetite
  • disrupt digestion
  • increase the body's demand for energy

Examples of these types of conditions include childhood cancers, congenital heart diseasecystic fibrosis and cerebral palsy.

Some children may become malnourished because of an eating disorder or a behavioural or psychological condition that means they avoid or refuse food.

Malnutrition caused by a poor diet is rare in the UK, but it can happen if a child is neglected, living in poverty or being abused.

Call the NSPCC helpline on 0808 800 5000 if you're concerned about a child.


Treatment for malnutrition (undernutrition) depends on the underlying cause and how malnourished the person is.

You may be given advice to follow at home, or be supported at home by a dietitian or other qualified healthcare professional. In severe cases, treatment in hospital may be needed.

The healthcare professional in charge of your care must ask for your consent to treatment when starting or stopping nutrition support. If you're unable to give your consent, they must act in your best interest following medical guidelines.

Dietary changes and supplements

A dietitian will advise about dietary changes that can help.

They may create a tailored diet plan that ensures you get enough nutrients.

They may also suggest:

  • having a healthier, more balanced diet
  • eating "fortified" foods that contain extra nutrients
  • snacking between meals
  • having drinks that contain lots of calories
  • getting supermarket deliveries at home

If these measures are not enough, taking extra nutrients in the form of supplements may be recommended. These should only be taken on the advice of a healthcare professional

You'll have regular appointments to check that any changes to your diet are helping to improve your nutrition. Your diet may need to be adjusted to make it more effective.

Feeding tubes

If you are unable to eat enough to meet your body's needs – for example because you have problems swallowing (dysphagia) – an alternative way of getting nutrients may be needed.

This can include:

  • using a tube that's passed through your nose and down into your stomach (nasogastric tube)
  • using a tube that's placed directly into your stomach or gut through the skin on your tummy (percutaneous endoscopic gastrostomy - PEG - tube)
  • using a solution containing nutrients that[s fed directly into your blood through a tube in a vein (parenteral nutrition)

These treatments are usually started in hospital, but they can be continued at home if you are well enough.

See treatment for swallowing problems for more information about these feeding methods.

Care and support services

Some people who are malnourished need extra care to help them cope with underlying issues such as limited mobility.

This may include:

  • home care visitors who can help you to shop for food or cook if you find this difficult
  • occupational therapy – an occupational therapist can identify problems with daily activities and help find solutions
  • a "meals on wheels" or meals at home service – this can often be provided by the local authority, although there's usually a charge
  • speech and language therapy – a speech therapist can teach exercises to help with swallowing problems and give advice about dietary changes (such as foods that are easy to swallow)

Treating malnutrition in children

Malnutrition in children is often caused by long-term health conditions, for which hospital treatment is needed. But this is not the case for all children with malnutrition.

Treatment may involve:

  • dietary changes, such as eating foods high in energy and nutrients
  • support for families to help them manage factors affecting the child's nutritional intake
  • treatment for any underlying medical conditions causing  malnutrition
  • vitamin and mineral supplements
  • high energy and protein nutritional supplements – if the other treatments are not enough on their own

Severely malnourished children need to be fed and rehydrated with great care. They cannot be given a normal diet immediately. They'll usually need special care in hospital.

Once they're well enough, they can gradually return to a normal diet and continue this at home.

It's important that treatment is monitored regularly to make sure it's working. Weight and height measurements will be taken, and a child will be referred to specialist services if there's no improvement.

The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website
Last Updated: 05/03/2024 13:00:00