Introduction

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

Malnutrition means "poor nutrition" and can refer to:

  • undernutrition – when you don't get enough nutrients
  • overnutrition – when you get more nutrients than you need

This topic focuses on undernutrition. See obesity for more information about the main problems associated with overnutrition.

Who's affected by malnutrition?

Malnutrition is a common health problem. There are an estimated 3 million malnourished people in the UK at any time, with many more at risk of becoming malnourished.

Around one in three people admitted to hospital or care homes in the UK are found to be malnourished or at risk of malnourishment.

Malnutrition is caused by having an inadequate diet or a problem absorbing nutrients from food. There are many reasons why these might happen, including having reduced mobility, a long-term health condition, or a low income.

Read more about the causes of malnutrition

Signs of malnutrition

The most common symptom of undernutrition is unintentional weight loss (losing 5-10% or more of your body weight over three to six months).

Other signs can include:

  • weak muscles
  • feeling tired all the time
  • low mood
  • an increase in illnesses or infections 

The main sign of overnutrition is being overweight or obese. However, people with undernutrition can also be overweight if they eat a diet high in energy (calories), but low in other nutrients.

Signs of malnutrition in children can include failure to grow at the expected rate and changes in behaviour, such as appearing unusually irritable, sluggish or anxious.

Your child’s weight and physical development should be regularly assessed by your GP when your child is young. Speak to your GP or health visitor if you have any concerns about your child’s health or development.

Read more about the symptoms of malnutrition

When to see your GP

See your GP if your body mass index (BMI) is lower than 18.5 or you notice the above symptoms. 

BMI is a measure of whether you're a healthy weight for your height. You can use the BMI healthy weight chart to work out your BMI.

You should visit your GP if you believe you or someone you care for is at risk of malnutrition. They can check for signs of malnourishment and any conditions that may cause malnutrition.

Read more about diagnosing malnutrition

Treating malnutrition

Depending on what's caused a person to become malnourished and how severe it is, treatment may be carried out at home or in hospital.

Dietary changes are the main treatment for malnutrition. If you're undernourished, you may need to increase the nutritional content of your food, with or without taking nutritional supplements.

If you're unable to eat enough to meet your nutritional needs you may need:

  • a feeding tube to provide nutrients directly into your digestive system
  • a drip to provide nutrients and fluids directly into a vein

Read more about treating malnutrition

Preventing malnutrition

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

A healthy, balanced diet is vital for maintaining health and fitness. To stay healthy, you need to eat a variety of foods from the four 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

The eatwell guide shows the different types of food you need to eat (and in what proportions) to maintain a well-balanced and healthy diet.

Read more about preventing malnutrition

Symptoms

The most common symptom of malnutrition is unplanned and unexplained weight loss.

Adults

If you lose 5-10% or more of your body weight within three to six months and you're not trying to lose weight, it could be a sign that you're at risk of malnourishment.

Sometimes, weight loss isn't obvious because it occurs slowly, over time. You may notice that your clothes, belts and jewellery gradually feel looser.

Other signs of malnutrition may include:

  • feeling tired all the time and lacking energy
  • frequently getting infections 
  • taking a long time to recover from infections
  • delayed wound healing 
  • poor concentration
  • difficulty keeping warm
  • depression

A good way of assessing whether you're malnourished is to work out your body mass index (BMI). BMI is a measurement that shows whether you're a healthy weight for your height.

For most adults a healthy BMI is between 18.5 and 24.9. Having a BMI under 18.5 could suggest you're at a high risk of being malnourished, although you may also be considered at risk if you have a BMI between 18.5 and 20.

It's important to note that BMI and weight loss aren't the only indicators of malnutrition. A person can be overweight or obese and still be malnourished. This can be due to having a diet consisting of food and drink that's high in fat and sugar but low in essential vitamins and minerals.

When to see your GP

See your GP if your BMI is lower than 18.5, you've lost more than 5-10% of your body weight over the last three to six months, or you experience the symptoms listed above.

Children

Symptoms of malnutrition in children can include:

  • failure to grow at the expected rate, both in terms of weight and height (known as "failure to thrive")
  • changes in behaviour, such as being unusually irritable, sluggish or anxious
  • changes in hair and skin colour

When to see your GP

Your child’s weight and physical development should be regularly assessed by your GP or a health visitor during your child's first few years of life.

Contact your GP if you have any concerns about your child’s health or development.

Causes

Malnutrition is caused by a lack of nutrients in your diet.

This is either due to an inadequate diet or problems absorbing nutrients from food.

Medical conditions

Medical conditions that can lead to malnutrition include:

  • a condition that causes a lack of appetite, such as cancer, liver disease, persistent pain or nausea
  • a mental health condition, such as depression or schizophrenia, which may affect your ability to look after yourself
  • a health condition that requires frequent hospital admissions
  • a health condition that disrupts your body’s ability to digest food or absorb nutrients, such as Crohn's disease or ulcerative colitis
  • dementia – people with dementia may be unable to communicate their needs when it comes to eating
  • dysphagia – a condition that makes swallowing difficult or painful 
  • persistent vomiting or diarrhoea 
  • an eating disorder, such as anorexia nervosa

Some types of medication may increase your risk of developing malnutrition. More than 250 types of medicine are known to disrupt the body’s ability to absorb and then break down nutrients.

You may also be at risk of becoming malnourished if your body has an increased demand for energy – for example, if it's trying to heal itself after major surgery, or a serious injury such as a burn, or if you experience involuntary movements, such as a tremor.

Physical factors

Physical factors can also contribute to malnutrition. For example:

  • if your teeth are in a poor condition, or if dentures don't fit properly, 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 situations that can contribute to malnutrition include:

  • living alone and being socially isolated
  • having limited knowledge about nutrition or cooking
  • reduced mobility
  • alcohol or drug dependency
  • low income or poverty

Children

In the UK, the most common causes of malnutrition in children are long-term health conditions that:

  • cause lack of appetite
  • disrupt the normal process of digestion
  • cause the body to have an increased demand for energy

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

In the UK, malnutrition as a result of inadequate food intake is rare, although it may occur if a child is neglected, living in poverty or being abused. If you're concerned that a child may be at risk of neglect or abuse, call the NSPCC child protection helpline on 0808 800 5000.

Sometimes, children become malnourished because they avoid eating due to issues with their body image.

Diagnosis

Several factors are taken into account to check whether someone is malnourished or at a high risk of malnutrition.

In adults, these include:

  • body mass index (BMI) – a measure that can be used to determine if you're a healthy weight for your height
  • whether you've unintentionally lost weight in recent months
  • whether an illness means you're unable to feed yourself or absorb nutrients from your diet

You would normally be considered malnourished if you have a BMI of less than 18.5 or you've unintentionally lost more than 5% of your body weight during the last three to six months. However, in some cases, doctors may be concerned about malnutrition if you have a BMI between 18.5 and 20.

You may be considered at a high risk of malnutrition if:

  • an illness means you have eaten nothing for the last five days, or you're likely to eat nothing for the next five days
  • you don't absorb nutrients from food well – for example, you have a condition, such as Crohn’s disease, that causes the digestive system to become inflamed
  • there's an underlying reason why your body is likely to use up nutrients at a higher rate or have an increased need for nutrients
  • you have difficulty eating and drinking

A vitamin or mineral deficiency can usually be diagnosed with a blood test.

Diagnosing malnutrition in children

Diagnosing malnutrition in children involves taking a measurement of their weight and height and comparing it against the expected average height and weight for a child of that age.

Some children will be below average because they're naturally smaller, but a significant drop below the expected level could indicate a risk of malnutrition.

Blood tests can also be used to measure protein levels in the blood. Low levels of protein may suggest that a child is malnourished.

Treatment

Treatment for malnutrition depends on the underlying cause and how malnourished a person is.

You may be given advice to use at home, or you may be treated at home under the supervision of a dietitian or other qualified healthcare professional. In some cases, hospital admission will be necessary.

Treatment at home

If you're treated under supervision at home, the healthcare professional helping you will discuss with you changes you should make to your diet.

Your dietary plans will depend on your individual circumstances, but it's likely you'll be advised to gradually increase your intake of energy (calories), protein, carbohydrates, fluids, and vitamins and minerals. The aim is to reduce your risk of developing complications, such as infections, and to avoid hospital admission.

The British Dietetic Association (BDA) has produced a factsheet called Malnutrition – overcoming the problem (PDF, 560kb), which provides some useful practical advice.

You may also be advised to take special nutritional supplements which can increase your energy and protein intake. You'll be helped to set targets and your progress will be regularly monitored.

Depending on the cause of your malnutrition, you may also need additional help. For example, you may benefit from the help of a carer if poor mobility makes it difficult for you to shop for food or cook.

Read more about getting care at home

If you have problems swallowing food or drink (dysphagia), you may be referred to a speech and language therapist (SLT) who can assess your swallowing and offer advice about a special diet that can help.

If you can't eat enough to meet your body's needs, an artificial method of feeding may be required, such as a feeding tube. These are fitted in hospital but can be used at home (see below). 

Treatment in hospital

You'll be seen by a number of healthcare professionals if you're admitted to hospital with malnutrition. They may include:

  • a doctor who specialises in treating digestive conditions (a gastroenterologist)
  • a dietitian
  • a nurse who specialises in nutrition 
  • a social worker

If you don't have problems swallowing food, dietary changes may be recommended, with or without nutritional supplements.

If you're unable to swallow food you may need a feeding tube. There are two types of feeding tubes:

  • a nasogastric tube – a tube that's passed down your nose and into your stomach
  • a percutaneous endoscopic gastrostomy (PEG) tube – a tube that's surgically placed directly into your stomach through your abdomen (tummy)

Parenteral nutrition

If a feeding tube isn't suitable, it may be necessary to deliver nutrition directly into your bloodstream through a drip into your vein. This is known as parenteral nutrition and it allows you to receive nutrients that you can't get through eating.

You'll be prescribed a solution that's tailored to your individual dietary needs. The solution may include a combination of nutrients, including carbohydrates and sugars, proteins, fats, electrolytes (salts) and a variety of vitamins and minerals.

Additional treatment

The underlying cause of your malnutrition may also need to be treated.

The amount of time you'll spend in hospital will depend on your general state of health and what's causing your malnutrition. In some cases it may be possible to return home while receiving treatment.

Treating children

In the UK, many cases of malnutrition in children are caused by long-term health conditions and hospital treatment is often required.

Childhood malnutrition can sometimes be treated with additional nutrients. Your child may need to take special supplements and eat foods high in energy and nutrients. The underlying cause of their malnutrition may also need to be treated.

Severely malnourished children need to be fed and rehydrated with great care and so can't be given a normal diet straight away. Once their condition stabilises they can gradually be introduced to a normal diet.

Malnutrition due to lack of food is a child protection issue, which means the police and social services need to be informed.

Prevention

The best way to ensure you get the correct amount of nutrients is to eat a healthy, balanced diet.

healthy, balanced diet contains foods from all the major food groups.

The four main food groups are:

  • fruit and vegetables – at least 5 a day
  • bread, rice, potatoes, pasta, cereals and other starchy foods
  • milk and dairy foods – such as cheese and yoghurt
  • meat, fish, eggs, beans, nuts, and other non-dairy sources of protein

Foods and drinks high in fat or sugar aren't essential for most people and should only be consumed in small amounts.

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

If malnutrition (or risk of malnutrition) is caused by an underlying health condition, you may have more complex dietary needs or you may need additional items in your diet such as nutritional supplements. Your GP or the doctor in charge of your care will be able to advise you and refer you to a registered dietitian.

Also on NHS inform