Synopsis
Identify undernutrition at any body size, choose safe and consented nutrition support, and prevent or treat refeeding electrolyte, thiamine, fluid and cardiac complications.
- Malnutrition can occur at any BMI, including obesity, oedema, pregnancy and after bariatric surgery; weight alone is not a nutritional assessment.
- NICE considers nutrition support when BMI is below 18.5, unintentional loss exceeds 10% in three to six months, or BMI below 20 accompanies more than 5% loss.
- Little or no intake for more than five days also creates nutrition-support need and refeeding considerations even when formal BMI criteria are not met.
- Use a validated screening tool such as MUST, then assess cause, trajectory, muscle, swallowing, gastrointestinal function, cognition, capacity and goals of care.
- High refeeding risk is present with one major criterion such as BMI below 16, loss above 15%, no intake above ten days or low potassium, phosphate or magnesium.
- Risk also exists with two moderate criteria: BMI below 18.5, loss above 10%, no intake above five days, or alcohol or relevant medicine history.
- Give thiamine and balanced vitamin supplementation before and during early feeding, and prescribe potassium, phosphate and magnesium replacement from the outset unless levels are already high.
- NICE starts high-risk feeding at no more than 10 kcal/kg/day, using 5 kcal/kg/day in extreme cases, then advances toward need over four to seven days.
- Pre-feeding correction of low electrolytes is not routinely necessary before any nutrition begins, but replacement and close monitoring must start immediately with expert oversight.
- Fluid and sodium can cause as much harm as calories; record balance, weight, oedema, heart rate, blood pressure and respiratory status.
- Oral, enteral and parenteral routes follow swallowing safety and gastrointestinal function, with informed consent, capacity assessment and a reviewable treatment goal.
- When malnutrition is linked to an eating disorder, alcohol dependence, neglect or inability to obtain food, combine medical stabilisation with mental-health, safeguarding and social support.
Key red flags
A falling phosphate, potassium or magnesium after nutrition starts with oedema, weakness, arrhythmia, respiratory difficulty or neurological change indicates clinically important refeeding physiology.
Confusion, ataxia, eye-movement abnormality, neuropathy, lactic acidosis or cardiac failure in an undernourished person warrants immediate thiamine before glucose where possible.
Rapid weight gain, oedema, rising respiratory rate, crackles, raised venous pressure or falling oxygenation after feeding suggests sodium-water retention and cardiac stress.
Bradycardia, hypotension, hypothermia, syncope, severe electrolyte change, suicidality or uncontrolled purging requires same-day eating-disorder and acute medical assessment under current NICE and local criteria.
Investigation priorities
Identify risk from BMI, weight loss and acute intake reduction consistently.
Management branches
Hospital admission, first relevant outpatient contact or clinical concern about intake or weight loss.
- Use MUST or the local validated tool, obtaining recent weight trajectory and intake duration and adapting measurements for oedema, disability or inability to stand.
- Assess disease cause, swallowing, GI function, muscle and function, alcohol, medicines, mental health, food access, capacity and the person's treatment goals.
- Refer at-risk patients to dietetics or the nutrition-support team and begin a documented oral, enteral or parenteral plan matched to urgency and refeeding risk.