Malnutrition is a serious condition that occurs when a person’s diet does not contain the right amount of nutrients.

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

Who is affected?

Malnutrition is a common health problem. It is estimated there are about 3 million people who are malnourished in the UK at any time and 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 either an inadequate diet or a problem absorbing nutrients from food. There are many reasons why this might happen, including having reduced mobility, a long-term health condition or a low income.

Read more about the causes of malnutrition.

What are the signs of malnutrition?

The most common symptom of undernutrition is unplanned weight loss (usually losing more than 5-10% of your body weight within three to six months), although 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
  • 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 or a health visitor in their first few years of life. Speak to them if you have any concerns about your child’s development or health.

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 experience the symptoms listed above. 

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.

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

Read more about diagnosing malnutrition.

How is malnutrition treated?

Depending on the cause and severity of your malnutrition, treatment may be carried out at home or in hospital.

The main treatment for people diagnosed with malnutrition is dietary changes. If you are undernourished, this may involve increasing the nutritional content of your food, with or without taking nutritional supplements.

If you are unable to eat enough to meet your nutritional needs, there are two main treatment options:

  • a feeding tube can be used to provide nutrients directly into the digestive system
  • a drip can be used to provide nutrients and fluids directly into a vein

Read more about treating malnutrition.

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