Malnutrition & Refeeding Syndrome

Malnutrition develops when intake is too low (poor appetite, nausea, pain on eating, swallowing difficulty, depression, limited food), when absorption is poor (for example in coeliac disease, Crohn disease, pancreatic insufficiency or after bowel surgery), when losses are high (vomiting, diarrhoea, fistulas), or when the body needs more than usual (infection, cancer, burns, chronic inflammation). Refeeding syndrome happens after prolonged low intake: when feeding restarts, insulin rises and pulls phosphate, potassium and magnesium into cells, so their blood levels drop. Risk is higher with very low body weight, recent rapid weight loss, little or no food for many days, alcohol dependence, and long-term illness.

Malnutrition is common in people with digestive and liver diseases such as inflammatory bowel disease, coeliac disease, pancreatic disease, cirrhosis, bowel obstruction, cancer and after some operations. It also affects older people, people with swallowing problems, depression, eating disorders or alcohol dependence, and people with limited access to food. It is often under-recognised, so screening is valuable. Refeeding syndrome is less common but can be life-threatening in those at risk.

During Ramadan or other periods of fasting, people who are malnourished, pregnant, elderly, or who have a digestive or liver illness should speak to their doctor before fasting, as it may not be safe. Traditional foods such as dates, labneh, nuts, tahini, eggs and olive oil can be used to add energy and protein.

Doctors and dietitians use simple screening questions about recent weight loss and appetite, measure weight, height and body mass index, and look for loss of muscle and fat. Blood tests can show anaemia, low vitamins and minerals, and poor kidney or liver function; blood protein levels alone are not a reliable measure of nutrition. If you are at risk of refeeding syndrome, phosphate, potassium, magnesium and blood sugar are checked before and during feeding. Further tests look for the cause of the poor intake or absorption, such as coeliac blood tests, stool tests, scans or endoscopy.

If you are only mildly underweight and well, small steps can help. If you have eaten very little for many days, do not restart a full diet on your own; see a doctor first.

• Eat little and often: aim for three meals and two or three snacks a day rather than waiting for hunger.

• Weigh yourself weekly at the same time and keep a record to show your doctor.

• Gentle activity, such as walking and light strength exercises, helps to rebuild muscle once your team agrees.

• Do not use fad diets, long fasting or unprescribed supplements to gain or lose weight.

• Tell your doctor about low mood, difficulties with swallowing, dental problems or money worries that limit your eating.

The aim is to increase energy and protein in manageable amounts. A dietitian can create a plan that suits your condition, taste and culture.

• Add energy to normal foods: olive oil, butter or ghee, full-fat milk or yoghurt, nuts, nut butters, tahini, dates, and eggs.

• Include a protein source at every meal, such as fish, chicken, meat, eggs, legumes, dairy.

• Prescribed oral nutritional supplement drinks can be used between meals when advised.

• If you have a condition such as coeliac disease or lactose intolerance, adjust the foods you choose; do not simply remove food groups on your own.

• After a long period of little food, your team may start nutrition at a low level and increase it over several days; follow their plan exactly.

Medicines are used to treat the cause, replace missing nutrients and prevent refeeding problems. Your doctor decides what you need; do not start supplements in high amounts on your own.

• Vitamin B1 (thiamine) is usually given before and during refeeding in people at risk.

• Phosphate, potassium and magnesium are replaced by tablets or drips guided by blood tests.

• Multivitamins, iron, vitamin D, vitamin B12 or other supplements are given when tests show a deficiency.

• Medicines for nausea, pain or diarrhoea, or to treat the underlying disease, may help you eat better.

When eating by mouth is not enough or not possible, nutrition can be given in other ways under medical supervision.

• A thin feeding tube through the nose into the stomach or bowel (nasogastric tube) can provide liquid feeds in the short term.

• For longer feeding support, a tube placed into the stomach through the skin (gastrostomy) may be arranged.

• If the gut cannot be used, nutrition can be given into a vein (parenteral nutrition) in hospital or sometimes at home with specialist support.

• Procedures such as endoscopy may be used to find and treat the cause, for example a narrowing.

Current practice recommends screening everyone in healthcare settings for malnutrition risk, identifying people at risk of refeeding syndrome before feeding starts, and beginning nutrition support at a low level and increasing it gradually, with vitamin B1 (thiamine) and mineral replacement and close monitoring. Early nutrition support is encouraged because delaying it can worsen outcomes.

Most people improve with the right nutrition support and treatment of the underlying cause, although recovery of weight and strength can take weeks to months. Refeeding syndrome is largely preventable when it is recognised and feeding is restarted slowly under supervision. Untreated malnutrition can lead to complications, so seek help early.

• How much weight should I regain, and how quickly?

• Am I at risk of refeeding syndrome, and do I need to be monitored?

• Which vitamin and mineral levels should be checked?

• Do I need supplement drinks or tube feeding?

• What is causing my poor intake or absorption, and how will it be treated?

This guide comes from the Saudi Gastroenterology Association (SGA) patient library, prepared by the Approved for publication by SGA; individual clinician review is ongoing. Last reviewed: 2026-04-24. It is for education and does not replace your doctor's advice.