Refeeding Syndrome: Causes, Risks and How It’s Prevented

If you or someone you care about has been eating very little or has lost a significant amount of weight, you may have heard the term refeeding syndrome. It can sound frightening, particularly when increasing food is exactly what someone needs in order to recover.

Refeeding syndrome is a potentially serious complication that can occur when nutrition is reintroduced after a period of starvation, malnutrition or severe dietary restriction. Importantly, the risk is well understood and can usually be managed safely when it is identified in advance and refeeding takes place with appropriate medical and dietetic supervision.

What is refeeding syndrome?

During a prolonged period of very restricted eating, the body adapts to having less energy available. Insulin levels fall and the body increasingly uses stored fat and protein for energy.

At the same time, the body’s overall stores of important electrolytes and vitamins can become depleted. These include phosphate, potassium and magnesium.

When carbohydrate-containing food is reintroduced, insulin levels rise again. This causes glucose to move into cells for energy, while phosphate, potassium and magnesium move into the cells at the same time. As a result, levels of these electrolytes in the bloodstream can fall rapidly.

Phosphate is particularly important because cells need it to produce and use energy. A significant fall in phosphate, known as hypophosphataemia, is one of the characteristic biochemical features associated with refeeding syndrome.

Changes in potassium, magnesium, thiamine and fluid balance can occur alongside this. If severe, these disturbances can affect the heart, lungs, muscles, nervous system and other organs.

This is why increasing nutrition after significant malnutrition needs to be carefully planned rather than approached simply as a matter of “eating more”.

Refeeding syndrome is particularly relevant for some people receiving treatment for anorexia nervosa and other eating disorders involving severe or prolonged restriction, although it can occur in people who are malnourished for many different reasons.

What are the initial symptoms of refeeding syndrome?

Early symptoms can include fatigue, weakness, muscle weakness, swelling or fluid retention and feeling generally unwell. However, changes in blood electrolytes can occur before obvious symptoms develop, so symptoms alone cannot determine whether refeeding is safe.

Possible symptoms and complications include:

• increasing fatigue or weakness
• muscle weakness, cramps or twitching
• swelling of the legs, ankles or other parts of the body
• nausea or digestive symptoms
• dizziness or changes in blood pressure
• changes in heart rate or heart rhythm
• breathlessness
• confusion or other neurological changes.

In severe cases, refeeding syndrome can cause serious cardiac, respiratory or neurological complications and can be life-threatening if untreated.

Anyone who develops significant breathlessness, chest symptoms, collapse, marked confusion, severe weakness or another acute deterioration during refeeding requires urgent medical assessment.

Refeeding syndrome: who is at risk?

Not everybody with an eating disorder will develop refeeding syndrome.

Risk increases when the body has experienced significant malnutrition, rapid weight loss or an extended period with very little nutritional intake.

Healthcare professionals therefore assess refeeding risk before substantially increasing nutritional intake, taking into account weight, weight change, recent food intake, blood results, medical history and overall clinical condition.

NICE guidelines: criteria for high risk of refeeding problems

NICE identifies adults as being at high risk if they have one or more of the following:

• BMI below 16 kg/m²
• unintentional weight loss of more than 15% within the previous three to six months
• little or no nutritional intake for more than 10 days
• low levels of potassium, phosphate or magnesium before feeding.

Alternatively, someone is considered at high risk if they have two or more of the following:

• BMI below 18.5 kg/m²
• unintentional weight loss of more than 10% within the previous three to six months
• little or no nutritional intake for more than five days
• a history of alcohol misuse, or use of certain medicines including insulin, chemotherapy, antacids or diuretics.

These criteria should be interpreted by an appropriately trained healthcare professional rather than used for self-assessment.

It is also important to understand that normal blood results before refeeding do not necessarily mean there is no risk. The body’s overall electrolyte stores can be depleted even when blood levels initially appear normal. It is when nutrition and insulin increase that electrolyte levels may fall.

For this reason, clinicians look at the whole clinical picture rather than relying on a single blood test.

How soon can refeeding syndrome be corrected?

When refeeding problems are recognised promptly, electrolyte abnormalities can often begin to be corrected over a period of days through appropriate replacement, adjustment of nutritional intake and close medical monitoring.

There is no single timeframe because treatment depends on which abnormalities are present and how severe they are.

Someone with mild biochemical changes will have very different treatment needs from someone who is medically unstable or experiencing significant cardiac or neurological complications.

If phosphate, potassium or magnesium levels fall during refeeding, the medical and dietetic team can determine what supplementation is required, whether the nutritional plan needs adjusting and how frequently blood tests or physical observations are needed.

More severe refeeding syndrome requires hospital-based medical treatment.

How to avoid refeeding syndrome

The safest way to avoid refeeding syndrome is to identify people at risk before refeeding begins and introduce nutrition according to an individual medical and dietetic plan, with appropriate monitoring and replacement of electrolytes and vitamins where required.

Safe refeeding may involve:

• assessing refeeding risk before substantially increasing nutritional intake
• agreeing an appropriate starting nutritional prescription
• gradually progressing nutrition according to clinical need
• monitoring phosphate, potassium, magnesium and other relevant blood results
• monitoring physical observations and fluid balance where indicated
• providing thiamine and other vitamin supplementation where clinically appropriate
• replacing electrolytes where necessary
• reviewing the plan regularly as nutritional intake increases.

Exactly how quickly nutrition should be increased is an individual clinical decision. It depends on factors including the degree of malnutrition, recent intake, blood results and physical health.

A specialist eating disorder dietitian can assess nutritional requirements and develop an appropriate plan for safely increasing intake. Medical oversight from a GP, psychiatrist or hospital team may also be needed to arrange blood tests, physical observations and prescribe vitamin or electrolyte supplementation.

NICE guideline CG32, Nutrition support for adults, is one of the main UK sources of guidance for identifying adults at high risk of refeeding problems and planning safe nutrition support.

Which healthcare professionals manage refeeding syndrome in the UK?

Refeeding risk is usually managed by a multidisciplinary team. Depending on the person’s level of risk and physical health, this may include a specialist eating disorder dietitian, GP, psychiatrist, nursing staff and, where hospital care is required, an acute medical or paediatric team.

At The London Centre, we can provide specialist eating disorder assessment, dietetic support and psychiatric oversight alongside psychological treatment.

Where blood tests, ECGs or physical observations are needed, these are coordinated with the person’s GP or other appropriate medical services.

For people who are medically stable enough to remain in the community but require more support than standard weekly outpatient treatment, we can also provide structured multidisciplinary care through our Intensive Outpatient Programme.

However, outpatient treatment is not a substitute for hospital care where someone is medically unstable. If there are concerns about acute physical risk, urgent medical assessment is required.

Refeeding syndrome should not become a reason to delay nutritional rehabilitation. Continued starvation and malnutrition carry significant risks of their own. The aim is therefore to increase nutrition in a planned and monitored way, with the right level of specialist support.

If you are worried about your own eating or about someone close to you who has been eating very little, losing weight rapidly or preparing to begin nutritional rehabilitation, please contact The London Centre for Eating Disorders and Body Image to discuss an appropriate specialist assessment.

If someone is acutely physically unwell or medically unstable, seek urgent medical care through NHS emergency services rather than waiting for an outpatient appointment.

Frequently Asked Questions

Is refeeding syndrome fatal?

Refeeding syndrome can be fatal if severe electrolyte and fluid disturbances are left untreated, particularly because they can affect the heart, respiratory system and nervous system. With appropriate risk assessment, monitoring and medical management, however, refeeding problems can usually be identified and treated.

Can refeeding be done safely at home?

Nutritional rehabilitation can often be done safely while living at home, but someone at significant risk of refeeding syndrome should not manage the process alone. Appropriate medical and dietetic supervision, blood monitoring and physical observations may be required. People who are medically unstable may require hospital care.

Does everyone with anorexia develop refeeding syndrome?

No. Not everyone with anorexia develops refeeding syndrome. Risk is greatest in people who are significantly malnourished, have lost substantial weight or have had very little nutritional intake for an extended period.

What blood test is most associated with refeeding syndrome?

A fall in serum phosphate is one of the hallmark biochemical changes associated with refeeding syndrome. Potassium and magnesium can also fall, while thiamine deficiency and changes in fluid balance may contribute to complications.

Where can I find UK guidelines for preventing refeeding syndrome?

NICE guideline CG32, Nutrition support for adults, sets out UK criteria for identifying adults at high risk of developing refeeding problems and principles for safely introducing nutrition. Individual treatment should always be determined by appropriately qualified healthcare professionals.

For more information, please download our Refeeding Syndrome information sheet.