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 calculator 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:

The eatwell plate 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.



Middle aged and underweight

A dietitian explains how middle-aged and older people can become underweight, with tips on how to eat the right diet and put weight on the healthy way.

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Next review due:

Page last reviewed: 21/01/2015

Next review due: 21/01/2017