Nursing care
Anorexia Nervosa nursing care: what to assess and what to do first
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Anorexia nervosa nursing care centres on medical stabilisation before psychiatric work begins, because starvation itself is the acute threat. The priority is cardiac and electrolyte assessment, with refeeding syndrome as the leading cause of death during treatment. Phosphate is the value to track most closely once feeding starts, alongside potassium, magnesium and cardiac rhythm.
The pathophysiology in one pass
Prolonged caloric restriction forces the body to shift from glucose to fat and protein for fuel. Insulin secretion drops, and the body conserves energy by slowing every system it can: heart rate falls, blood pressure drops, the gut slows, and the endocrine axis that drives menstruation and bone turnover shuts down. Muscle wasting includes cardiac muscle, so the heart itself shrinks and weakens.
The danger reappears the moment feeding resumes. A starved body that suddenly receives carbohydrate responds with a surge of insulin, which drives phosphate, potassium and magnesium out of the blood and into cells. Phosphate is the one to watch: it is used up fast by the newly reactivated cells, and severe hypophosphataemia can trigger cardiac arrhythmia, respiratory failure and sudden death. This is refeeding syndrome, and it is the leading cause of death during treatment, not the starvation state itself.
Assessment findings that matter
Vital signs come first. Bradycardia, orthostatic hypotension and hypothermia reflect the body's energy-conserving state and correlate with the severity of malnutrition, not just body weight. A resting heart rate below 40 bpm or a systolic drop of more than 20 mmHg on standing signals a patient who needs closer monitoring than the ward routine allows.
Look beyond the vital signs chart. Lanugo hair, dry skin, brittle nails and peripheral oedema (from low albumin, not fluid overload) are visible markers of prolonged restriction. Check for Russell's sign on the knuckles if purging behaviours coexist, and ask directly about laxative or diuretic use, since patients under-report both. Baseline bloods should include phosphate, potassium, magnesium, glucose and an ECG before any feeding plan starts, because these values set the safe starting point and the frequency of rechecks that follow.
What the exam asks about this
Exam questions on this topic are built around prioritisation, and refeeding syndrome is the answer they are usually steering toward. A stem describing a severely malnourished patient who is about to start enteral or oral feeding is testing whether you know to start low and monitor phosphate, not whether you know the calorie target.
Expect vignettes that give a phosphate value dropping over the first days of feeding and ask what to do next, or a scenario where a patient develops confusion, weakness or an arrhythmia shortly after feeding begins. The correct response is usually to slow or hold the feed and notify the provider, not to push through with the nutrition plan. Questions may also test whether you recognise that a normal or even elevated weight does not rule out dangerous electrolyte disturbance.
Nursing interventions in priority order
Cardiac and metabolic stabilisation comes first. That means continuous or frequent vital sign monitoring, telemetry where the patient's condition warrants it, and daily electrolyte panels including phosphate during the first week of refeeding, tapering as levels stabilise. Weigh the patient at a consistent time, in the same clothing, after voiding, because weight manipulation is common and the trend matters more than any single number.
Nutrition rehabilitation follows a conservative, stepwise increase in calories rather than an aggressive catch-up approach, guided by the treatment team's protocol. Supervise meals and the period afterward to reduce opportunity for purging or food disposal, and maintain a neutral, non-punitive tone during observation. Only once the patient is medically stable does the focus shift toward the psychological work: building trust, addressing body image distortion, and involving the patient in their own care planning where they are able to engage safely.
Medications and monitoring
Anorexia nervosa has no medication that treats the eating disorder itself; drug therapy addresses complications and comorbid conditions. Phosphate, potassium and magnesium replacement are given as levels fall during refeeding, often before they drop below the lab's normal range, since a normal value today can be a dangerously low one within 24 to 48 hours of feeding.
Antidepressants and antipsychotics are sometimes used for comorbid depression, anxiety or obsessive features, but they are adjuncts, not primary treatment, and evidence for their effect on the eating disorder itself is limited. Monitor QT interval closely if any QT-prolonging medication is added, since the starved heart is already vulnerable to arrhythmia. Thiamine is often given before or alongside carbohydrate refeeding to prevent precipitating Wernicke's encephalopathy in a depleted patient.
When to escalate
Escalate immediately for a falling phosphate, potassium or magnesium during the refeeding period, for any new arrhythmia or a heart rate change outside the patient's established baseline, or for signs of heart failure such as new oedema, shortness of breath or jugular venous distension. These findings point toward refeeding syndrome or cardiac decompensation and need provider notification without delay.
Escalate too for suicidal ideation, a body mass index or vital sign pattern that meets criteria for higher-level or inpatient medical care, or a patient who refuses feeding to a degree that threatens medical stability. Institutional protocols vary on the exact thresholds for ICU transfer, nasogastric feeding, or involuntary treatment, so follow your facility's eating disorder or refeeding protocol rather than a single fixed number.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our mental health practice questions are the closest set to what this page covers.
Common questions
What electrolyte is most important to monitor in anorexia nervosa?
Phosphate is the electrolyte most closely tied to refeeding syndrome, the leading cause of death during treatment. It falls sharply once feeding restarts because insulin drives it into cells, so it needs frequent rechecking in the first days of nutrition rehabilitation even if the baseline value looked normal.
Why does refeeding syndrome happen?
A starved body running on fat and protein suddenly gets carbohydrate again, which triggers a surge of insulin. That insulin drives phosphate, potassium and magnesium out of the bloodstream and into cells faster than the depleted body can replace them, which can cause arrhythmia and respiratory failure.
What vital sign changes are expected in anorexia nervosa?
Bradycardia, hypotension and hypothermia are expected as the body conserves energy under prolonged restriction. These are not incidental findings; their severity tracks with how depleted the patient is and should shape how closely they are monitored.
Should nutrition be increased quickly once a patient starts feeding?
No. Feeding is started conservatively and increased in stepwise increments guided by the treatment protocol and daily electrolyte results, not advanced quickly to make up lost weight. A rapid increase is what precipitates refeeding syndrome.
What should the nurse do if phosphate drops after feeding starts?
Hold or slow the feeding plan as directed and notify the provider promptly, since a falling phosphate signals refeeding syndrome in progress. Replacement is typically started before the level falls into a critically low range.
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