Refeeding syndrome in adults (Guidelines)

TAM (Treatments and Medicines) NHS Highland
NHS Highland

Audience

  • Secondary care only
  • Adults only

What is refeeding syndrome?

Refeeding syndrome (RFS) describes a series of metabolic and biochemical changes that occur as a consequence of reintroduction of feeding after a period of starvation or fasting (Khan et al, 2011). RFS leads to severe fluid and electrolyte shifts (most notably hypophosphataemia), with related metabolic and potentially life threatening complications. In hospital practice, malnourished patients commencing any form of nutritional support (oral, enteral or parenteral) are most at risk.

Quick reference guide

1. Assess risk:

Identify patient at risk of RFS via presence of one or more of the following:

  • BMI<16kg/m2
  • Unintentional weight loss of greater than 15% in ≤ 6months
  • Very little or no food for > 10 days
  • Low levels of potassium, phosphate or magnesium prior to feeding
  • BMI<18.5kg/m2

OR presence of two or more of the following:

  • Low levels of potassium, phosphate or magnesium prior to feeding
  • BMI<18.5kg/m2
  • Unintentional weight loss of greater than 10% in ≤ 6months
  • Very little or no food for > 5 days

2. Refer to dietetics:

  • If assessed as high risk (see diagnosis section)

3. Check electrolyte levels: 

Prior to feeding check serum sodium, potassium, urea, creatinine, magnesium, phosphate, and albumin adjusted calcium levels.  Replace electrolytes if low according to serum levels.  Do NOT delay feeding

4. Prescribe and administer vitamins:  

Route of administration will depend upon the severity of re-feeding risk and access available. Prescribe and administer B vitamins at least 30 minutes before feeding commences, for 7 to 10 days (once patients meet their full nutritional requirements by feeding, ongoing supplementation is unlikely to be needed)

Intravenous access:

  • Thiamine 200mg IV daily
  • After 72 hours change to oral/enteral thiamine 200mg daily, vitamin B co strong 1 to 2 tablets (can be crushed), 3 times daily, and forceval 1 capsule once daily, consider additional ascorbic acid supplementation if at risk of deficiency
  • If no enteral access, continue iv thiamine until an oral/enteral route is established

Oral/Enteral:

  • Thiamine 200mg daily
  • Vitamin B compound strong 1 to 2 tablets, 3 times daily
  • Forceval capsule once daily
  • Consider additional ascorbic acid supplementation if at risk of deficiency

5. Introduce feed slowly:

For individuals receiving oral nutrition support: 

  • Diet as able only, until dietetic review

For individuals receiving artificial enteral nutrition:

  • Refer to starter regimens for introducing enteral feed until the patient has been reviewed by a dietitian (Appendix – link to guideline).

For individuals receiving parenteral nutrition:

  • Prescribe Regimen 1 @ 26ml/hour over 24hours until the patient has been reviewed by a dietitian (Appendix – link to guideline)

6. Monitor:

Monitoring of blood results:

  • Check for electrolyte disturbances daily for at least 5 days after feeding is commenced, during replacement therapy, and, until results are stable
  • Note that biochemical measures may be within normal levels prior to feeding, but could decrease during feeding
  • Be aware of malnourished, dehydrated patients with renal impairment and consequently normal or high electrolyte levels

Monitoring of clinical condition:

  • Ensure careful, appropriate restoration of circulatory volume, whilst monitoring pulse and fluid balance.  May need additional IV fluids
For electrolyte replacement see table

Baseline

 Daily for at least 5 days or until stable Weekly until discharge

Bloods

 FBC, U&Es, Mg2+, PO43-, Ca2+

U&Es, Mg2+, PO43-, Ca2+

U&Es, Mg2+, PO43-, Ca2+
Observations Body weight, neurological signs or symptoms of RFS.

Temperature (4 hourly), blood glucose (BM once daily), pulse & respirations (once daily), body weight.

 Body weight
Food intake and fluid balance

Accurate input & output charts.

 Accurate input & output charts.  

Causes of refeeding syndrome

During starvation, the use of glucose (from carbohydrate digestion) is reduced leading to the catabolism of protein and release of free fatty acids from fat stores to mobilise non-carbohydrate sources for energy production (Friedi et al, 2018).

There is a resultant loss of body fat and protein, and depletion of water, micronutrients and electrolytes. Notably there is a depletion of total body potassium, magnesium and phosphate.

Although serum concentrations are maintained, intracellular stores are depleted (PENG, 2018).

Refeeding of patients after a time period of starvation causes a shift in metabolism from a catabolic to an anabolic state. There is a consequential release of insulin to support carbohydrate metabolism and this drives glucose, potassium, phosphate and magnesium to the intracellular compartment. There is also a rapid depletion of thiamine, a co-factor in carbohydrate metabolism (Stanga et al 2008).

Subsequently, this may result in; hypophosphatemia, hypokalaemia, hypomagnesaemia, hypocalcaemia, thiamine deficiency and/or retention of sodium and water (Mehanna et al 2008).

Risk factors for refeeding syndrome

NICE guidelines CG32 provides a useful framework for identifying risk of RFS; however it is recognised that risk factors are only true risk factors in the presence of starvation (NICE, 2006) During any initial assessment the following patients should be considered for possible risk of RFS:

  • Patients with very poor dietary intake prior to admission
  • Any malnourished patient planned to commence nutritional supplementation (enteral, including oral, or parenteral)
  • Any inpatient who has had prolonged periods of being nil by mouth including post-operative patients for >7 days
  • Any patient with a compromised nutritional status due to increased nutrient losses or decreased nutrient absorption, such as prolonged (over 4 to 10 days) diarrhoea or vomiting, chronic pancreatitis, dysfunction/inflammation of the GI tract, or post bariatric surgery
  • Anorexia nervosa. For further guidance please refer to TAM guidelines for management eating disorders
  • Patients with a history of high alcohol intake
  • Oncology patients undergoing treatment such as chemotherapy
  • Patients with insulin dependent diabetes
  • Hyperemesis of pregnancy

Diagnosis of refeeding syndrome

Refeeding syndrome occurs when there is an unbalanced and too rapid reintroduction of nutrition in at risk patients. This typically occurs within 72 hours after feeding recommences (either oral or artificial) and therefore close monitoring is recommended during the first 4 days of re-feeding (Friedli et al, 2017). The symptoms of RFS can be wide ranging and have a systemic effect. Some of these features can be seen below. Due to their non- specific nature, RFS should be suspected in any patient who exhibits signs of deterioration after re-feeding commences:

 

Features
Hypophosphataemia

Altered myocardial function, arrhythmia, congestive heart failure, acute ventilatory failure, lethargy, weakness, seizures, confusion, coma, paralysis, acute renal failure, nausea, anorexia.
Hypokalaemia

Arrhythmia, cardiac arrest, respiratory distress, paralysis, weakness, rhabdomyolysis, polyuria, polydipsia, decreased GFR, constipation, ileus, glucose intolerance.
Hypomagnesaemia

Arrhythmia, tachycardia, ataxia, muscle tremors, confusion, weakness, tetany, respiratory depression, diarrhoea, constipation, abdominal pain, hypokalaemia, hypocalcaemia.
Thiamine deficiency

Congestive heart failure, lactic acidosis, Wernicke-Korsakoff syndrome, muscle weakness.
Hypernatraemia

Heart failure and arrhythmia, respiratory failure, pulmonary oedema, renal failure, muscle cramps, fluid retention and oedema.

Key clinical presentations of the biochemical abnormalities seen in RFS (Khan et al 2010)

At risk:

  • Those who have had very little or no food intake for >5 days.
  • People with normal prefeeding levels of potassium, magnesium and phosphate can still be at risk

High risk:
People with any one of the following:

  • BMI <16g/m2
  • Unintentional weight loss >15% within the last 3 to 6 months,
  • little or no nutritional intake for more than 10 days,
  • low levels of potassium or phosphate or magnesium prior to feeding

OR

People with two or more of the following:

  • BMI <18kg/m2,
  • unintentional weight loss >10% within the last 3 to 6 months,
  • little or no nutritional intake for more than 5 days,
  • low levels of potassium or phosphate or magnesium prior to feeding,
  • a history of alcohol abuse,
  • or those taking drugs that can influence electrolyte levels, such as insulin, chemotherapy, antacids or diuretics.

Management of refeeding syndrome

High risk: should be referred to the dietetic department.

Individuals at risk: can be managed at local level using the following recommendations:

  • Monitor electrolytes daily, including potassium, magnesium and phosphate, and replace according to treatment regimens.
  • People at risk of refeeding in the community, e.g anorexia, ARFID, disease associated malnutrition, alcohol dependence should be considered for oral thiamine supplementation

Treatment: Replacement of electrolytes

Caution needs to be taken with people who have ultra-low body weight, and referral to paediatric electrolyte and volume replacement guidance may be appropriate, using a weight based calculation for electrolytes and circulating blood volume. Fluids and electrolytes | Treatment summaries | BNFC | NICE

Electrolyte

Parenteral replacement

 Enteral replacement
Phosphate
  • If <0.32mmol. (Can also be considered if levels of 0.32 to 0.5mmol if compliance/access issues)
  • Give PHOSPHATES POLYFUSOR: 500ml infused over 12 hours at 40ml/hr, via a dedicated cannula. A single 12 hour infusion is usually sufficient but must be repeated daily if phosphate remains low until phosphate > 0.50mmol/l.
  • If 0.32 to 0.5mmol with enteral access
  • Give Phosphate Sandoz 2 tablets three times daily

Magnesium

See separate TAM guideline for further details if eGFR <30mL/min
  • If <0.5mmol OR 0.5 to 0.7mmol and symptomatic. (Can be considered if levels of 0.5 to 0.7mmol and compliance/access issues)
  • 20mmol magnesium sulphate available as 10mmol in 250ml 0.9% sodium chloride infused over 3 hours.
  • 10mmol may be given over 2 hours if symptomatic. Cardiac monitoring recommended.
  • In patients who are fluid restricted 10mmol may be given in 100ml 0.9% sodium chloride.
  • A preparation can be made in 5% glucose if hypernatraemia is a concern.
  • Give a total of three doses at 12 hour intervals: ie dose 1 at t = 0 hours, dose 2 at t = 12 hours and dose 3 at t = 24 hours.
    This may not be enough to replete magnesium stores and treatment may need to be continued.
  • If 0.5 to 0.7mmol with enteral access and asymptomatic
  • Oral or via enteral feeding tube: The contents of one magnesium aspartate dihydrate oral powder sachet (Magnaspartate®) (10mmol Mg) once or twice daily.
Potassium
  • If <2.5mmol. (Can also be considered if 2.5 to 3.0mmol)
  • Give 40mmol potassium chloride (KCl) in 1 litre 0.9% sodium chloride or 5% glucose, infused over 4 hours via peripheral cannula. (Maximum 3mmol/kg per day.)
  • Give oral potassium IN ADDITION to IV
  • A more concentrated solution of potassium may be available when patients cannot tolerate these volumes for administration via central access on Critical Care.
  • If 2.5 to 3.5mmol with enteral access
  • Give Sando K®, 2 tablets 3 times daily, up to 3 tablets 4 times daily

General guidance:

  • Monitor electrolytes daily for at least first 5 days of feeding.
  • Pre-feeding, normalisation of electrolytes is not necessary and may extend the period without nutrition (NICE 2006).
  • Continue feeding whilst correcting any deranged electrolyte level. Do not stop the feeding plan whilst correcting electrolyte abnormalities
  • Avoid long term phosphate replacement in patients with Chronic Renal Failure.
  • Up to 160mmol of Mg2+ ≥ 5 days may be required to correct hypomagnesaemia.
  • Ensure low magnesium is corrected to ensure hypokalaemia responds to replacement.

Abbreviations

  • ARFID: Avoidant / restrictive food intake disorder
  • BMI: body mass index
  • eGFR: estimated glomerular filtration rate 
  • RFS: Refeeding syndrome 

Editorial Information

Last reviewed: 28/08/2025

Next review date: 31/08/2028

Author(s): Gastroenterology, Nutrition.

Version: 1

Approved By: TAM subgroup of the ADTC

Reviewer name(s): C Fraser, Gastroenterology Consultant, Z Mrevlje-Simon, Gastroenterology Consultant, L Macleman, Dietician.

Document Id: TAM686