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Malnutrition

Also called Undernutrition

Malnutrition is when your diet does not contain the right amount of nutrients. It usually means undernutrition, from not eating enough, but it can also mean lacking specific vitamins and minerals. It is more common in older people, people with long-term illnesses, and people who find it hard to eat, absorb food or afford it.

Last updated Nov 9, 2026

What it is

It can weaken the immune system, slow healing, cause tiredness and increase the risk of falls.

Treatment includes dietary advice, nourishing foods and drinks, supplements and treating any underlying cause, sometimes with help from a dietitian.

Common signs

  • Unintentional weight loss
  • Loss of appetite
  • Tiredness and weakness
  • Getting ill often and taking longer to recover
  • Clothes or rings becoming loose

How it is usually diagnosed

  • Weight and BMI checks over time
  • Screening tools such as MUST
  • Blood tests

Records worth keeping

Keeping these together makes each appointment easier, especially when you see a new doctor:

  • Weight records over time
  • Nutrition screening scores
  • Blood test results
  • Dietitian plans

Questions to ask your doctor

  • What is causing my weight loss?
  • Should I see a dietitian?
  • Do I need supplements?

When to get help right away

Call 112 or go to the nearest emergency department if you have:

  • Severe weakness, confusion, fainting or being unable to eat or drink: get urgent medical help

This page is general information. It is not a diagnosis and does not replace a doctor who knows your history. Medfold keeps your records organised; it does not interpret them.

Sources

Related conditions

Coeliac diseaseAn autoimmune condition in which eating gluten damages the lining of the small bowel. It is treated with a lifelong gluten-free diet.Anorexia nervosaA serious eating disorder in which a person keeps their weight low by eating too little or exercising too much. Recovery is possible with support.Iron deficiency anaemiaToo little iron means the body cannot make enough healthy red blood cells. Finding the reason for the low iron matters as much as treating it.