Malnutrition is a serious condition that occurs when a person’s diet doesn't contain the right amount of nutrients.

It means "poor nutrition" and can refer to:

  • undernutrition – not getting enough nutrients
  • overnutrition – getting more nutrients than you need

This topic focuses on undernutrition. 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 5-10% or more of weight over three to six 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)
  • 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

Read more about the symptoms of malnutrition.

When to see your GP

See your GP if:

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

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

Your GP can check if you're at risk of malnutrition by measuring your weight and height, asking about any medical problems you have, and asking about 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 be affected, but it's more common in:

Elderly people are particularly at risk, and weight loss is not an inevitable result of old age.

Read more about the causes of malnutrition.

Treatments for malnutrition

Treatment depends on the person’s general health and how severely malnourished they are.

The first dietary advice is usually:

  • eating "fortified" foods that are high in calories and protein
  • snacking between meals
  • having 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 this may have happened.. 

If these initial dietary changes aren't enough, a doctor, nurse or dietitian may also suggest taking extra nutrients in the form of nutritional drinks or supplements.

If the person has difficulty eating that can't be managed by making changes such as eating soft or liquid food, other treatments may be recommended, such as:

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

Read more about how malnutrition is treated.

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 bread, rice, potatoes, pasta and other starchy foods
  • some milk and dairy foods
  • some meat, fish, eggs, beans and other non-dairy sources of protein

See the Eatwell Guide for more information about the types of food that should make up your diet and the proportions you should eat them in.

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


The main symptom of malnutrition (undernutrition) is unintended weight loss, although this isn't 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.

Someone could be malnourished if:

  • they unintentionally lose 5-10% of their body weight within three to six months
  • their 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 your GP if you've unintentionally lost a lot of weight over the last few months.

If you notice 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 or depression

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

Contact your 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 in your diet, either due to a poor diet or problems absorbing nutrients from food.

Certain things can increase a person's risk of becoming malnourished.

Health conditions

Some 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.


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

Some medicines have unpleasant side effects – such as loss of appetite, diarrhoea or nausea – that 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 disease, cystic 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 as a result of a poor diet is rare in the UK, but may occur 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.

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

Dietary changes and supplements

A dietitian will advise about dietary changes that can help.

They may create a tailored diet plan that ensures the person gets 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 home supermarket deliveries

If these measures aren’t enough, taking extra nutrients in the form of supplements may be advised. These should only be taken on the advice of a healthcare professional

For more information and advice, see:

Feeding tubes

For people who are unable to eat enough to meet their body's needs – for example because they have swallowing problems – an alternative way of getting nutrients may be needed.

This can include:

  • a tube that's passed down the nose and into the stomach – called a nasogastric tube
  • a tube that's placed directly into the stomach or gut through the skin of the tummy
  • a solution containing nutrients being fed directly into the blood through a tube in a vein – known as parenteral nutrition

These treatments are usually first started in hospital, but they can be continued at home if the person is well enough.

Read about how swallowing problems are treated for more information about these feeding methods.

Care and support services

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

This may include:

  • home care visitors who can help shop for food or cook for people who find this difficult 
  • occupational therapy – an occupational therapist can identify problems with daily activities and help find solutions to these
  • 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 difficulties and offer 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 often needed. But this isn't 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 manage underlying factors affecting the child's nutritional intake
  • treatment for any underlying medical conditions causing their malnutrition
  • vitamin and mineral supplements
  • high energy and protein nutritional supplements – if the other treatments aren't enough on their own

Severely malnourished children need to be fed and rehydrated with great care so can't be given a normal diet straight away. They will 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. Regular weight and height measurements will be taken, with referral 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 nhs.uk
Last Updated: 15/10/2019 11:02:00