Published September 9, 2024
The Medical Warning Signs of an Eating Disorder Every Provider Should Know
By Jessica Setnick, MS, RD, CEDS-C
The short version
Medical instability in eating disorders is read from vital signs and labs, not from how thin a patient looks. The most dangerous signs are bradycardia, hypotension, orthostatic changes, hypothermia, and electrolyte disturbances, especially low potassium. A patient at a 'normal' weight can be in acute crisis.
Eating disorders carry among the highest mortality rates in psychiatry, from medical complications and from suicide. The complications are largely reversible with nutrition and correction, which is exactly why catching them early matters so much.
If you remember one thing: a resting heart rate in the 40s, orthostatic vital-sign changes, or a potassium below 3.0 is a reason to act now, regardless of the number on the scale.
Vital signs that should stop you
Bradycardia is the classic and most important finding. In severe restriction the body slows the heart to conserve energy; a resting heart rate below 50, and certainly below 40, signals significant medical compromise and often warrants a higher level of care. Check it at rest and take it seriously even in a patient who feels 'fine.'
Orthostatic vital signs reveal instability the resting numbers may hide. A meaningful rise in heart rate or drop in blood pressure from lying to standing points to dehydration and cardiovascular strain. Hypotension and hypothermia, a core temperature that runs cold, round out the picture of a body running on too little fuel.
These are objective, cheap, and fast. A manual pulse, a blood pressure cuff, and an orthostatic check give you more real information about danger than a visual assessment of the patient's body ever will.
Labs that signal danger
Electrolytes are the labs that kill. Hypokalemia, low potassium, is the most urgent, often driven by vomiting, laxative, or diuretic use, and it can trigger fatal arrhythmias. Low sodium, low phosphate, and low magnesium all matter, and phosphate becomes especially critical as you begin to refeed.
Look wider too. Restriction and purging can produce metabolic alkalosis, elevated liver enzymes from starvation, low blood sugar, low white cell and platelet counts from marrow suppression, and an elevated BUN from dehydration. A patient can have a normal-looking chart one week and a dangerous one the next, so serial labs beat a single snapshot.
Interpret labs in context. 'Normal' electrolytes in a severely restricting or purging patient can be deceptively reassuring, the body compensates until it suddenly can't. Trend matters as much as any single value.
Physical exam and history clues
On exam, watch for lanugo, the fine downy hair the body grows to stay warm, hair loss, dry skin, cold and mottled extremities, and edema. In patients who vomit, look for dental erosion, parotid gland swelling that gives a 'chipmunk' appearance, and calluses on the knuckles, Russell's sign.
History fills in the rest: amenorrhea or menstrual irregularity, syncope and dizziness, cold intolerance, chronic constipation and reflux, and unexplained GI complaints. Any of these in combination should prompt a full screen and a set of vitals and labs.
None of these signs requires specialty training to catch. A primary care provider, an ER nurse, or a therapist who knows to ask about fainting and to request a potassium level is often the person who catches the danger first.
When to escalate
Escalate to medical stabilization or a higher level of care for severe bradycardia, significant orthostatic changes, dangerous electrolyte derangement, hypoglycemia, or any acute mental-status change. When in doubt about cardiac risk, get an ECG, prolonged QT and arrhythmia are the mechanisms of sudden death here.
Do not let a normal or high body weight talk you out of concern. Atypical anorexia patients present with the full range of these complications, and their instability is routinely underestimated precisely because they don't look the part.
Knowing which numbers cross the line, and how to communicate urgency to a patient and family without inducing panic, is core clinical competency. The medical monitoring framework, including refeeding, is taught step by step in the Boot Camp and covered in the Pocket Guide.