The main symptom of malnutrition (undernutrition) is unintended weight loss, although this is not always obvious.

Weight loss

Most people who are malnourished will lose weight, but it's possible to be a healthy weight or even overweight and still be malnourished.

For example, this can happen if you're not getting enough nutrients, such as some types of vitamins and minerals, through your diet.

You could be malnourished if:

• you unintentionally lose 5 to 10% of your body weight within 3 to 6 months
• your 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 a GP if you have unintentionally lost a lot of weight over the past few months.

If a friend or family member has lost a lot of weight, talk to them about your concerns and encourage them to get help.

Other symptoms

Other symptoms of malnutrition include:

• reduced appetite
• lack of interest in food and drink
• 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 a GP if you have these symptoms. If you notice them in someone else, try to encourage them to get help.

Symptoms in children

Symptoms of malnutrition in a child can include:

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

See a GP if you're concerned about your child's health or development at any point.

Malnutrition (undernutrition) is caused by a lack of nutrients, either as a result of a poor diet or problems absorbing nutrients from food.

Certain things can increase your risk of becoming malnourished.

Health conditions

Some health conditions that can lead to malnutrition include:

• long-term conditions that cause loss of appetite, feeling sick, vomiting and/or changes in bowel habit (such as diarrhoea) – these include cancer, liver disease and some lung conditions (such as chronic obstructive pulmonary disease)
• mental health conditions, such as depression or schizophrenia, which may affect your mood and desire to eat
• conditions that disrupt your ability to digest food or absorb nutrients, such as Crohn's disease or ulcerative colitis
• dementia, which can cause a person to neglect their wellbeing and forget to eat
• an eating disorder, such as anorexia

You can also become malnourished if your body needs an increased amount of energy – for example, if you're healing after surgery or a serious injury such as a burn, or if you have involuntary movements such as a tremor.

Medicines

Some types of medicine may also increase your risk of developing malnutrition.

Some medicines have unpleasant side effects, such as making you feel sick, losing your appetite, or having diarrhoea, which could mean you eat less or do not absorb as many nutrients from food.

Physical and social factors

The following factors can also contribute to malnutrition:

• teeth that are in poor condition, or dentures that do not 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 often caused by long-term health conditions that:

• lead to a 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 caused by a poor diet is rare in the UK, but it can happen 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 a person is.

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

The healthcare professional in charge of your care must ask for your consent when starting or stopping nutrition support. If you're unable to give your consent, they must act in your best interest following medical guidelines.

Dietary changes and supplements

A dietitian will advise you about dietary changes that can help.

They may create a tailored diet plan that ensures you get 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 supermarket deliveries at home

If these measures are not enough, taking extra nutrients in the form of supplements may be recommended. These should only be taken on the advice of a healthcare professional.

You'll have regular appointments to check that any changes to your diet are helping to improve your nutrition. Your diet may need to be adjusted to make it more effective.

Feeding tubes

If you are unable to eat enough to meet your body's needs – for example because you have problems swallowing (dysphagia) – an alternative way of getting nutrients may be needed.

This can include:

• using a tube that's passed through your nose and down into your stomach (nasogastric tube)
• using a tube that's placed directly into your stomach or gut through the skin on your tummy (percutaneous endoscopic gastrostomy – PEG – tube)
• using a solution containing nutrients that's fed directly into your blood through a tube in a vein (parenteral nutrition)

These treatments are usually started in hospital, but they can be continued at home if you are well enough.

See treatment for swallowing problems for more information about these feeding methods.

Care and support services

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

This may include:

• home care visitors who can help you to shop for food or cook if you find this difficult – read more about getting care at home
• occupational therapy – an occupational therapist can identify problems with daily activities and help find solutions
• 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 you exercises to help with swallowing problems and give advice about dietary changes (such as foods that are easy to swallow)

Find out how to feed someone you care for.

Treating malnutrition in children

Malnutrition in children is often caused by long-term health conditions, for which hospital treatment is needed. But this is not 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 help them manage factors affecting the child's nutritional intake
• treatment for any underlying medical conditions causing malnutrition
• vitamin and mineral supplements
• high-energy and protein nutritional supplements – if the other treatments are not enough on their own

Severely malnourished children need to be fed and rehydrated with great care. They cannot be given a normal diet immediately. They'll usually need special care in hospital.

Once they're well enough, they can gradually begin eating a normal diet and continue this at home.

It's important that treatment is monitored regularly to make sure it's working. Weight and height measurements will be taken, and a child will be referred to specialist services if there's no improvement.