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

These pages focus on undernutrition. Read about obesity for more about the problems associated with overnutrition.

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 weak
• getting ill often and taking a long time to recover
• in children, not growing or not putting on weight at the expected rate

Read more about the symptoms of malnutrition.

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 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.

Malnutrition is a common problem that affects millions of people in the UK.

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

• have a long-term health conditions that affect appetite, weight and/or how well nutrients are absorbed by the gut, such as Crohn's disease
• have problems swallowing (dysphagia)
• are socially isolated, have limited mobility, or a low income
• need extra energy, such as people with cystic fibrosis, are recovering from a serious injury or burns, and those with tremors (uncontrollable shaking)

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

Read more about the causes of 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 with underlying issues such as limited mobility. For example, care at home or occupational therapy.

If a child is malnourished, their family or carers 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 your 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

Read more about how malnutrition is treated.

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.

Further information

• baby weight and height
• underweight children aged 2 to 5
• underweight children aged 6 to 12
• underweight teen girls
• underweight teen boys
• underweight adults
• keeping your weight up in later life