UCL Institute of Mental Health



The extent of investigation should depend on the degree and duration of illness, the most likely causes and the clinical findings. In a patient who has an obvious cause for their catatonia or an established history of catatonia, minimal investigation beyond the basics might be appropriate.

Bedside investigations

  • Physical observations (pulse, blood pressure, respiratory rate, temperature, oxygen saturation). Repeat at least 3 times daily.
  • Food and fluid chart

Lorazepam challenge

If the diagnosis of catatonia is uncertain, the lorazepam challenge can help distinguish.

  1. Assess for features of catatonia at baseline, ideally using a scoring system such as the Bush-Francis Catatonia Rating Scale.
  2. Administer 1-2mg lorazepam by the intravenous, intramuscular or oral route.
  3. Re-assess after 5 minutes (intravenous), 15 minutes (intramuscular) or 30 minutes (oral). A 50% improvement suggests that catatonia is likely and that there is likely to be a good response to further treatment with benzodiazepines.
  4. If there is limited response, repeat the test with one further dose of lorazepam.

Blood tests

  • Full blood count
  • Electrolytes
  • Renal function
  • Bone profile
  • Liver function
  • Glucose
  • Thyroid function
  • Vitamin B12/folate
  • Creatine kinase
  • Iron
  • Copper and caeruloplasmin
  • HIV and syphilis serology
  • Antinuclear antibodies
  • Anti-NMDA receptor antibodies


  • Urinalysis for ketones
  • Urine drug screen
  • Electrocardiogram
  • Neuroimaging (MRI preferred to CT)
  • Electroencephalograph (EEG)
  • Lumbar puncture