Quick version
Blood tests and eating disorders at a glance
- Blood tests cannot diagnose an eating disorder on their own.
- They are used to assess physical effects, complications, and possible nutritional deficiencies.
- Common tests may include a complete blood count, sodium, potassium, creatinine, glucose, ALT, albumin, TSH, and free T4.
- In severe malnutrition, phosphate, magnesium, and calcium may also be important to monitor.
- Iron, ferritin, vitamin B12, and folate may be tested if anemia or nutritional deficiency is suspected.
- ECG, pulse, blood pressure, and weight development may also form part of the medical assessment.
- Normal blood test results do not rule out a serious eating disorder.
What is an eating disorder?
An eating disorder involves problems related to food, eating, weight, or body image that affect health and everyday life. Some of the most common diagnoses are anorexia nervosa, bulimia nervosa, and binge eating disorder, also known as BED.
Anorexia nervosa is characterized by severely restricted energy intake, low body weight, and an intense fear of gaining weight. Bulimia nervosa involves recurrent episodes of binge eating combined with compensatory behaviors, such as self-induced vomiting. Binge eating disorder involves recurrent episodes of binge eating without regular compensatory behaviors.
What is selective eating?
Selective eating can in some cases be part of ARFID, avoidant/restrictive food intake disorder. This condition involves a markedly restricted food intake, for example due to sensitivity to taste or texture, fear of unpleasant consequences from eating, or a low interest in food. It can lead to nutritional deficiencies, weight loss, or an impact on daily life.
Signs of an eating disorder
Signs may include that a person:
- skips meals or restricts food intake
- excludes an increasing number of foods or food groups
- becomes highly preoccupied with food, calories, weight, or exercise
- exercises excessively
- goes to the bathroom immediately after meals
- loses weight or does not follow expected weight development
- experiences fatigue, feeling cold, dizziness, constipation, or headaches
- shows changes in mood or withdraws from social situations involving food.
Can blood tests be used when evaluating eating disorders?
Blood tests cannot on their own determine whether a person has an eating disorder. The diagnosis is made through a combined medical and psychiatric assessment. Blood tests are instead used to assess whether the body has been affected, identify possible complications, and rule out other conditions that may cause similar symptoms.
Which tests are appropriate depends on factors such as the type of eating disorder, symptoms, weight development, degree of malnutrition, and whether the person, for example, vomits or uses laxatives or diuretics.
Complete blood count
Complete blood count provides information about hemoglobin, white blood cells, and platelets. Long-term or severe malnutrition can affect the blood count, and the test can also help identify conditions such as anemia.
Sodium and potassium
Sodium and potassium are important for the function of the nervous system, muscles, and heart. Abnormal levels may occur with dehydration, recurrent vomiting, or the use of laxatives or diuretics. Low potassium in particular may increase the risk of cardiac complications.
Creatinine
Creatinine is used as part of the assessment of kidney function and fluid balance. However, creatinine may be low in people with reduced muscle mass and should therefore be interpreted together with other clinical findings.
Glucose
Glucose may be measured to detect abnormal blood sugar levels. Low blood sugar can occur in severe starvation or malnutrition, while high blood sugar may indicate another disturbance in the body’s glucose regulation.
ALT and albumin
ALT may be used to assess possible liver involvement, which can occur in severe malnutrition.
Albumin may also be measured, but the level is influenced by several different factors and should not be used as a single marker of nutritional status.
TSH and free T4
TSH and free T4 may be measured to assess thyroid function and rule out thyroid disease as a possible cause of, for example, weight changes or other symptoms.
During prolonged starvation, thyroid hormone levels may also change as part of the body’s adaptation to low energy intake.
Phosphate, magnesium, and calcium
In severe malnutrition or before and during nutritional rehabilitation, phosphate, magnesium and calcium may need to be monitored. Abnormal levels are particularly important to identify in people at risk of developing refeeding syndrome.
Iron, ferritin, and other nutritional markers
If anemia, nutritional deficiency, or long-term restricted food intake is suspected, additional tests may be appropriate, such as ferritin, iron, vitamin B12 and folate.
The need for these tests is assessed individually based on symptoms, dietary intake, and other laboratory results.
Are other examinations needed?
In addition to blood tests, urine tests and an ECG may be included in the medical assessment.
ECG may be especially important in cases of significant weight loss, a low heart rate, electrolyte disturbances, or other signs of cardiac involvement. Blood pressure, pulse, temperature, and weight development are also important parts of the physical assessment.
When should you seek medical care?
It is important to seek medical care if an eating disorder is suspected, even if blood test results are normal. Normal laboratory results do not rule out a serious eating disorder or the need for treatment.
Urgent medical care should be sought in cases of severe weakness, fainting, palpitations, confusion, severe dehydration, or rapidly worsening general condition.
Blood tests are therefore an important part of the medical assessment, but they should always be interpreted together with symptoms, weight development, eating behavior, and other clinical findings.
