Skip to main content

Anorexia nervosa

Medical Professionals

Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Anorexia nervosa article more useful, or one of our other health articles.

Continue reading below

What is anorexia nervosa?

The World Health Organization (WHO) International Classification of Diseases 11th Revision (ICD-11) describes anorexia nervosa as follows:1

  • Anorexia nervosa is characterised by significantly low body weight for the individual’s height, age and developmental stage that is not due to another health condition or to the unavailability of food.

  • A commonly used threshold is body mass index (BMI) less than 18.5 kg/m2 in adults and BMI-for-age under 5th percentile in children and adolescents. Rapid weight loss (eg, more than 20% of total body weight within six months) may replace the low body weight guideline as long as other diagnostic requirements are met. Children and adolescents may exhibit failure to gain weight as expected based on the individual developmental trajectory rather than weight loss.

  • Low body weight is accompanied by a persistent pattern of behaviours to prevent restoration of normal weight, which may include behaviours aimed at reducing energy intake (restricted eating), purging behaviours (eg, self-induced vomiting, misuse of laxatives), and behaviours aimed at increasing energy expenditure (eg, excessive exercise), typically associated with a fear of weight gain. Low body weight or shape is central to the person's self-evaluation or is inaccurately perceived to be normal or even excessive.

How common is anorexia nervosa? (Epidemiology)2

  • The lifetime prevalence in women is reported to be between 2-4%.

  • Incidence rates vary from 4.2-12.6 per 100,000 person-years for females to 1 per 100,000 person-years for males.

  • Overall incidence rates are around 6.0 per 100 000 population with highest incidence in people aged 15-19 years.

Continue reading below

Anorexia nervosa causes (aetiology)2

The aetiology of anorexia nervosa is thought to be multifactorial, involving biological, psychological, developmental and sociocultural factors.3 It is not known whether a neurobiological vulnerability predisposes to anorexia nervosa or if this is associated with maintenance of symptoms once the illness develops. Further research is needed to examine the degree to which abnormalities are a consequence of starvation or are caused by an anorexia nervosa endophenotype.4 It may be that cultural, social and interpersonal elements can trigger onset, and changes in neural networks can sustain the illness.5

The main risk factors are thought to be:

  • Female gender.

  • Age.

  • Living in a Western society.

  • Family history of eating disorder, depression or substance misuse. Results of twin studies are inconclusive, with some suggesting a strong link, and others none.

  • Premorbid experiences. These include:

    • Sexual abuse.

    • Dieting behaviour within family or personal experience.

    • Occupational or recreational pressure to be slim (dancers, gymnasts, jockeys, models).

    • Onset of puberty.

    • Criticism or perceived criticism about weight or eating behaviour.

  • Personal characteristics:

    • Perfectionism.

    • Low self-esteem.

    • Obsessional traits.

    • Premorbid obesity.

    • Early menarche.

    • Difficulty with resolving conflict.

    • Anxiety.

    • Emotionally unstable personality disorder (formerly borderline personality disorder).

Anorexia nervosa symptoms and presentation2 6 7

Suspicion and diagnosis are based on history, suggestive clinical features and often concerns raised by a relative or friend. No single measure such as body mass index (BMI) can be used for either diagnosis or a decision about the need for treatment.

  • Anorexia nervosa can be difficult to detect in primary care. Those affected may be slow to present, or reluctant to disclose symptoms, or be unaware they have an eating disorder.

  • Do not use screening tools (eg, SCOFF) as the sole method to determine whether or not a person may have an eating disorder.

  • Assessment may be normal even in medically unstable people. Severe malnutrition and purging behaviours can lead to life-threatening complications such as cardiovascular instability or severe electrolyte disturbance. Have a low threshold for seeking advice, as emergency admission may be required.

Clinical features include:

  • Refusal to maintain a normal body weight for age and height.

  • Weight below 85% of predicted. This means in adults a BMI below 17.5 kg/m2. For those under 18 years of age, BMI centile charts should be used. In young people there may be a lack of appropriate weight gain, rather than weight loss.

  • Dieting or restrictive eating practices. Friends or family may report a change in eating behaviour.

  • Rapid weight loss.

  • Having a dread of gaining weight.

  • Disturbance in the way weight or shape is experienced, resulting in over-evaluation of size. Disproportion in concern about weight or shape.

  • Denial of the problem.

  • Lack of desire for intervention, or resistance to it.

  • Social withdrawal; few interests.

  • Enhanced weight loss by over-exercise, diuretics, laxatives and self-induced vomiting.

  • Problems managing pre-existing chronic diseases which involve dietary control, such as diabetes or coeliac disease.

Other physical features include:

  • In women, amenorrhoea for three months or longer. This was part of the defining criteria in the Diagnostic and Statistical Manual of Mental Disorders fourth edition (DSM-IV) classification, but was removed as being essential for a definition with the advent of DSM-5 in 2013.

  • Gastrointestinal symptoms are common, such as constipation, a feeling of fullness after meals, dysphagia and abdominal pains, and may hinder diagnosis and treatment.8

  • Symptoms such as fatigue, fainting, dizziness and intolerance of cold.

  • Delay in secondary sexual development if pre-puberty.


Examination should include:

  • Height, weight and BMI.

  • Core temperature.

  • Peripheral examination - circulation, oedema.

  • Cardiovascular examination - pulse, blood pressure, check for postural hypotension.

  • Testing of muscle power by using:

    • Sit up test - lay the person flat and ask them to sit up without using their hands.

    • Squat test - ask the person to squat and then stand up without using their hands.

Examination can be normal but findings could include bradycardia, hypotension, peripheral oedema, gaunt face, lanugo hair, scanty pubic hair, and acrocyanosis (hands or feet are red or purple).

Continue reading below


  • An ESR and TFTs are useful screens for other causes of weight loss.

  • Other tests will depend on the individual presentation.

  • U&Es should be checked in all those with behaviours such as vomiting, taking laxatives or diuretics or water loading.

  • In patients with eating disorders and BMI below 15, a history of purging or high risk markers, frequent testing for FBC, ESR, U&Es, creatinine, glucose, LFTs and TFTs is required.9

  • Consider a dual-energy X-ray absorptiometry (DXA) scan after a year of being underweight in those below 18 years of age (earlier if fractures or bone pain) and after two years in adults. Consider ongoing monitoring with DXA scans if they remain underweight, but no more often than every year.

  • An ECG may show bradycardia or a prolonged QT interval in those with more severe anorexia.

Assessing physical risk

The Management of Really Sick Patients with Anorexia Nervosa (MARSIPAN and MARSIPAN Junior) documents from the Royal Colleges of Psychiatrists, Physicians and Pathologists set out a risk assessment framework.10


In those aged 18 years or over, the following parameters suggest severe anorexia, and are a guide to the need for urgent referral and appropriate medical intervention. Risk increases with degree of abnormality and patients may need immediate referral, assessment and treatment:

  • Nutrition: BMI of 13-15 conveys medium risk; a BMI <13 is high risk. Note that BMI alone is not an adequate marker of medical risk.

  • Rate of weight loss: more than 0.5 kg per week.9

  • Pulse rate: below 40 beats per minute.

  • Blood pressure (BP): systolic BP below 90 mm Hg; diastolic BP below 70 mm Hg; postural drop greater than 10 mm Hg.9

  • Squat test: unable to get up from squatting or lying down without using arms for balance or leverage.

  • Core temperature below 35°C.

  • Blood tests: low potassium, sodium, magnesium or phosphate. Raised urea, creatinine or transaminases. Low albumin or glucose.

  • ECG: prolonged QT interval, T-wave changes, bradycardia.


In children and young people the risk parameters need adjustment for age and gender. Physiological measurements such as pulse and blood pressure differ from adults and by age, and BMI alone is an inadequate measure. MARSIPAN guidelines advocate using percentage BMI, which is measured as BMI/median BMI for age and gender x 100. Measuring this requires checking standard centile charts for the median BMI.11

Signs of moderate and severe risk, suggesting the need for urgent or immediate referral include:

  • BMI: medium risk is 70-80% of median BMI (0.4th to 2nd centile) and high risk is <70% (below the 0.2nd centile).

  • Rate of weight loss: medium risk is suggested by recent loss of weight of 500-999 g per week for two consecutive weeks; high risk is 1 kg or more over the same time frame.

  • Pulse rate: medium risk if the pulse rate whilst awake is below 50 beats per minute; high risk below 40 beats per minute.

  • Blood pressures: figures are dependent on age and gender but below the 2nd centile confers medium risk and below the 0.4th centile high risk.

  • Cardiovascular symptoms: a history of syncope and/or postural drops in blood pressure suggests higher risk.

  • ECG: an increase in the QT interval of 460 ms for girls or 400 ms for boys suggests medium or high risk, particularly in the presence of other rate or rhythm change.

  • Core temperature: <36°C suggests medium risk; <35.5°C high risk.

  • Blood tests: low potassium, sodium, calcium, phosphate, albumin or glucose.

  • Behaviour: severe restriction of calorie intake, moderate to high levels of excessive exercise, fluid restriction, vomiting, purging, poor insight, violent rebellion against parental input, suicidal behaviour and self-harm.

  • Squat test: unable to get up from a lying down position or from squatting without using arms for balance or leverage.

Anorexia nervosa treatment and management6

The National Institute for Health and Care Excellence (NICE) recommends that if an eating disorder is suspected, immediate referral be made to a community-based, age-appropriate eating disorder service for further assessment or treatment. The role of the GP is early detection, risk assessment, initial coordination of care, and sharing of ongoing monitoring. Latest guidelines stress the importance of early referral. Helping people with anorexia to reach a healthy body weight or BMI for their age is the key goal. The weight gain is central and is necessary to support any other treatments or changes which may be required in management of the condition.

Management for those under the age of 18 years12

Anorexia-nervosa-focused family therapy (FT-AN) for children and young people is currently considered first-line treatment for children and adolescents. This typically involves 18-20 sessions over a year and consists of three phases. It makes the role of the family key in the individual's recovery and gives control of the young person's eating in the first phase to the parents or carers. This allows individual tailoring of diets and eating regimes within the normal context of the young person. No blame should be attributed to either the person or their family. In the second phase, once weight has been restored, the person with anorexia is encouraged to take back some independence in managing their eating habits, and in the final phase planning is made to maintain recovery and prevent relapse. There is evidence for efficacy of this treatment.

Individual cognitive behavioural therapy (CBT) or adolescent-focused psychotherapy are alternatives if family therapy is inappropriate or ineffective.

Management for adults

Psychological treatment options for adults include:

  • Individual eating-disorder-focused cognitive behavioural therapy (CBT-ED). This typically involves 40 sessions over 40 weeks, starting more often than once per week.

  • Maudsley Anorexia Nervosa Treatment for Adults (MANTRA). This usually involves 20 sessions, weekly for the first ten weeks, then depending on response.

  • Specialist supportive clinical management (SSCM). This also involves 20 or more weekly sessions with a specialist practitioner.

If one of these options is ineffective or inappropriate, the others should be tried. An alternative is eating-disorder-focused focal psychodynamic therapy (FPT). A 2015 Cochrane review failed to find enough evidence to recommend one type of therapy over another and advised that larger trials are needed13 .

Management of physical complications

  • Monitoring of U&Es and regular ECGs may be required in severe cases.

  • Oral supplementation may be required to correct abnormal electrolyte balance, or IV if severe.

  • Advise regular assessment by a dentist if the person is vomiting regularly.

  • Seek specialist advice if reduced bone mineral density is diagnosed on DXA scan. Oestrogen treatment is not advised routinely for females with anorexia by NICE, but may be considered for girls aged 13-17 years who have long-term low body weight and low bone mineral density with a bone age over 15, and in physiological dosage in those with delayed puberty and a bone age under 15. Bisphosphonates may be useful in adults.

Management of those who are severely ill10

Urgent admission may be required if there is:

  • Electrolyte imbalance or hypoglycaemia.

  • Severe malnutrition.

  • Severe dehydration.

  • Evidence of incipient organ failure.

  • Bradycardia (below 40 beats per minute) or a prolonged QT interval on the ECG.

  • Very low BMI. Levels of risk are detailed above. BMI alone is not usually enough as a measure of high risk and other factors should be taken into consideration.

  • Rapid weight loss (eg, more than 1 kg per week for more than two consecutive weeks).

  • Need for medical stabilisation and refeeding.

  • Inability or incapacity of parents or carers to provide the support needed.

  • Significant suicide risk.

Admission is ideally to a specialist eating disorder unit with expertise to avoid deaths particularly from under-feeding or refeeding syndrome.

A clear plan and objectives are needed for treatment and the future for community follow-up after discharge, developed in collaboration with the person with anorexia and their family.

Other considerations for the management of anorexia nervosa

  • Age-appropriate multivitamin-and-mineral supplements should be advised as long as diet is inadequate to provide all necessary nutrients.

  • Dietary advice should be given as part of the multidisciplinary specialist approach.

  • Medication is not advised as the sole treatment for anorexia.

  • Advise avoidance of excessive exercise.

  • There is no evidence for efficacy of physical therapy options such as transcranial magnetic stimulation, acupuncture, weight training, yoga or warming therapy.

  • Collaboration between specialists may be needed where there is comorbid physical or mental illness.


  • Psychological and emotional disturbance - eg, anxiety, social withdrawal, poor quality of life, low mood and suicidal ideation.

  • Social difficulties - eg, disrupted relationships, isolation, limitations on employment prospects and economic disadvantage.

  • Family/carer stress.

  • Physical complications are usually secondary to compromised nutritional state and include:

    • Cardiovascular: arrhythmias, hypotension, valve prolapse, peripheral oedema, sudden death.

    • Musculoskeletal: loss of muscle strength, loss of bone density, fractures, impairment of growth in children and teenagers.

    • Endocrine: thyroid abnormalities, incomplete development of secondary sexual characteristics, impaired temperature regulation.

    • Gastrointestinal: slowed gastrointestinal motility, constipation, upper gastrointestinal bleeding, abnormal liver function tests, parotid gland enlargement.

    • Haematological: low white blood cell count (particularly neutrophils), anaemia, thrombocytopenia.

    • Metabolic: dehydration, electrolyte disturbance in those who misuse laxatives or diuretics or induce vomiting, re-feeding syndrome.

    • Neurological: cognitive impairment, seizures.

    • Renal: kidney stones and acute or chronic kidney disease (chronic volume depletion can lead to the development of kidney disease).

    • Dental: erosion of tooth enamel from vomiting.

    • Dermatological: dry skin, alopecia, lanugo hair and chilblains.

    • Obstetric and gynaecological: infertility, sexual dysfunction, risk of polycystic ovaries, miscarriage, hyperemesis, anaemia, intrauterine growth restriction, preterm birth, postpartum depression and anxiety.

    • Mortality: most deaths due to anorexia nervosa are a result of the medical consequences of starvation (especially cardiac and severe infection).


  • The course of anorexia nervosa is very variable. Estimates suggest 46% of people will fully recover, 34% improve partially and 20% develop a chronic eating disorder.

  • Up to 60% of adolescents with anorexia nervosa make a full recovery with early specialist treatment. Complete recovery is less likely the longer the person has the illness.

  • One study of the 30-year outcome of adolescent-onset anorexia nervosa found a favourable outcome regarding mortality and full symptom recovery. However, one in five had a chronic eating disorder.14

  • Poor prognosis is predicted by the need for hospitalisation and onset in adulthood.5 15

  • Relapse is common. One review found that 31% of people relapsed after treatment and the highest risk of relapse was during the first year after discharge.

  • There is a high risk of comorbid or subsequent psychiatric conditions, such as anxiety disorders, obsessive-compulsive disorder (OCD), depression and substance misuse.

  • Anorexia nervosa has a higher mortality rate than any other mental health disorder:

    • Mortality rates are over 5 times higher than the general population

    • The weighted crude mortality rate is around 5.1 deaths per 1,000 person-years. 20% of deaths are due to suicide.

    • The other most common causes of death are cardiac complications and severe infection.

Further reading and references

  • Costa MB, Melnik T; Effectiveness of psychosocial interventions in eating disorders: an overview of Cochrane systematic reviews. Einstein (Sao Paulo). 2016 Apr-Jun;14(2):235-77. doi: 10.1590/S1679-45082016RW3120.
  • Neale J, Hudson LD; Anorexia nervosa in adolescents. Br J Hosp Med (Lond). 2020 Jun 2;81(6):1-8. doi: 10.12968/hmed.2020.0099. Epub 2020 Jun 1.
  • Cost J, Krantz MJ, Mehler PS; Medical complications of anorexia nervosa. Cleve Clin J Med. 2020 Jun;87(6):361-366. doi: 10.3949/ccjm.87a.19084.
  1. International Classification of Diseases 11th Revision; World Health Organization, 2019/2021
  2. Eating disorders; NICE CKS, July 2019 (UK access only)
  3. Rikani AA, Choudhry Z, Choudhry AM, et al; A critique of the literature on etiology of eating disorders. Ann Neurosci. 2013 Oct;20(4):157-61. doi: 10.5214/ans.0972.7531.200409.
  4. Hay PJ, Sachdev P; Brain dysfunction in anorexia nervosa: cause or consequence of under-nutrition? Curr Opin Psychiatry. 2011 May;24(3):251-6.
  5. Treasure J, Claudino AM, Zucker N; Eating disorders. Lancet. 2010 Feb 13;375(9714):583-93.
  6. Eating disorders: recognition and treatment; NICE Guideline (May 2017 - last updated December 2020)
  7. Yeo M, Hughes E; Eating disorders - early identification in general practice. Aust Fam Physician. 2011 Mar;40(3):108-11.
  8. Malczyk Z, Oswiecimska JM; Gastrointestinal complications and refeeding guidelines in patients with anorexia nervosa. Psychiatr Pol. 2017 Apr 30;51(2):219-229. doi: 10.12740/PP/65274. Epub 2017 Apr 30.
  9. Professor Janet Treasure; A Guide to the Medical Risk Assessment for Eating Disorders, King's College London, 2012.
  10. Medical Emergencies in Eating Disorders: Guidance on Recognition and Management (Replacing MARSIPAN and Junior MARSIPAN); Royal College of Psychiatrists (May 2022)
  11. Body Mass Index (BMI) charts for girls and boys age 2-18; Royal College of Paediatrics and Child Health and Dept of Health
  12. Rienecke RD; Family-based treatment of eating disorders in adolescents: current insights. Adolesc Health Med Ther. 2017 Jun 1;8:69-79. doi: 10.2147/AHMT.S115775. eCollection 2017.
  13. Hay PJ, Claudino AM, Touyz S, et al; Individual psychological therapy in the outpatient treatment of adults with anorexia nervosa. Cochrane Database Syst Rev. 2015 Jul 27;(7):CD003909. doi: 10.1002/14651858.CD003909.pub2.
  14. Dobrescu SR, Dinkler L, Gillberg C, et al; Anorexia nervosa: 30-year outcome. Br J Psychiatry. 2020 Feb;216(2):97-104. doi: 10.1192/bjp.2019.113.
  15. Jagielska G, Kacperska I; Outcome, comorbidity and prognosis in anorexia nervosa. Psychiatr Pol. 2017 Apr 30;51(2):205-218. doi: 10.12740/PP/64580. Epub 2017 Apr 30.

Article history

The information on this page is written and peer reviewed by qualified clinicians.

symptom checker

Feeling unwell?

Assess your symptoms online for free