Blood SampleThere is significant practice variability when providers are asked to determine if a patient is intoxicated. Some providers will evaluate a patient to determine if a patient is “clinically sober”, while other providers will rely on a patient’s blood alcohol concentration (BAC) to evaluate a patient’s level of intoxication.  There is very little data to suggest that either approach is superior; however, both practice patterns have significant limitations and carry a certain degree of medicolegal risk. 

Both medical and legal literature supports the idea of determining if a patient is intoxicated using clinical criteria, which usually involves looking for obvious psychomotor and cognitive impairment. When determining if a patient is clinically sober, there are some significant limitations that a provider should consider.  

“Clinical sobriety” may not be obvious

A study of blunt trauma patients with acute alcohol use evaluated a provider’s ability to determine if a patient was “clinically sober.”  Patients with a blood alcohol concentration of <80 mg/dL were considered “sober” while patients above that threshold were considered to be intoxicated. Providers were asked to assess the patient and identify them as either sober or intoxicated.  The majority of the providers were able to correctly identify intoxicated patients, but were not able to reliably identify “sober” patients [1]. When evaluating a patient who had consumed alcohol but was not intoxicated, providers misidentified the patient as being intoxicated in ~2/3 of the cases. While providers tended to over classify patients as being intoxicated, they only missed 4% of patients with significant intoxication.

Olson et al. found that providers had difficulty predicting BAC in patients who had recently consumed alcohol and noted a tendency to overestimate BAC in non-chronic drinkers and underestimate this level in chronic drinkers. Across all ranges of BAC there was a poor correlation between degree of intoxication and the patient’s clinical presentation [2].

Obtaining a BAC can provide objective data in regards to a patient’s level of alcohol consumption, but ordering this test also has several important potential medicolegal implications.

Documenting a level can put a provider at risk

There is some evidence to suggest that obtaining a blood alcohol level may increase the provider’s risk of being sued. Simel et al. surveyed plaintiff’s attorney’s attitudes towards serum alcohol testing in the Emergency Department (ED). If a patient was seen in the ED for intoxication and had an accident after discharge, 43% of the attorneys would advise the patient to sue if an elevated BAC was documented. Only 17% of these attorneys would give similar advice in a situation where there was no BAC obtained. Of note if the same patient was discharged and specifically advised not to drive, only ~4% of attorneys would suggest that the provider was negligent even when a BAC was documented [3].

Never ignore an elevated level

All states consider a person to be “impaired” if their BAC is over 80-100 mg/dL. When a patient has a BAC at or above this level, they are legally intoxicated, despite their clinical appearance. There is very little legal support for the idea that a patient could be clinically sober while having an elevated BAC. Once an elevated BAC has been obtained, the provider is obligated to treat the patient as intoxicated, despite any clinical findings.

Patients with elevated BACs should be observed in the ED until they are no longer intoxicated.  This period of observation can severely impact departmental flow as multiple intoxicated patients may spend hours waiting until they are “sober”.  Most non-chronic drinkers will metabolize ethanol at a rate of 20 mg/dL/hr, so someone who presents with a BAC of 200 mg/dL will need to be watched for 5 -6 hours until their BAC would be below the legal limit of 80-100 mg/dL [4]. There is ongoing debate in regards to what constitutes an appropriate period of monitoring.  Some providers suggest monitoring the patient until they are both clinically sober and below the legal limit.  Other providers argue that patients should be monitored until they have metabolized essentially all of the alcohol in their system.

“Below the limit” might not be good enough

 A certain subset of patients will have a BAC that is below the legal threshold but may still show signs of intoxication that could put them at risk if they were to be discharged. This risk is supported by recent data that found an increased risk of injury in drivers who have a BAC < 80 mg/dL. Phillips et al. found that drivers who had BACs that were detectable but below the legal limit had a significant increase in accident severity when compared to drivers who had not consumed any alcohol [5]. When discharging a patient who had an elevated BAC, providers need to document that adequate time has passed for the BAC to drop, and also need to document that the patient appears clinically sober. 

Bottom Line

When approaching patients who have consumed alcohol, using a standard of clinical sobriety or relying on a BAC are both imperfect but reasonable approaches to determine if a patient is intoxicated. When using clinical criteria providers should be careful to not overestimate a patient’s level of intoxication. Using BAC to determine sobriety provides more precise data, but also creates clear evidence of intoxication that can potentially be used against a provider in the case of a bad outcome.  


  1. Mahler SA, Pattani S, Standifer J et-al. Clinical sobriety assessment by emergency physicians in blunt trauma patients with acute alcohol exposure. J Emerg Med. 2010;39 (5): 685-90. Pubmed
  2. Olson KN, Smith SW, Kloss JS et-al. Relationship between blood alcohol concentration and observable symptoms of intoxication in patients presenting to an emergency department. Alcohol Alcohol. 48 (4): 386-9. Pubmed
  3. Simel DL, Feussner JR. Does determining serum alcohol concentrations in emergency department patients influence physicians’ civil suit liability? Arch. Intern. Med. 1989;149 (5): 1016-8. Pubmed
  4. Gershman H, Steeper J. Rate of clearance of ethanol from the blood of intoxicated patients in the emergency department. J Emerg Med. 9 (5): 307-11. Pubmed
  5. Phillips DP, Brewer KM. The relationship between serious injury and blood alcohol concentration (BAC) in fatal motor vehicle accidents: BAC = 0.01% is associated with significantly more dangerous accidents than BAC = 0.00%. Addiction. 2011;106 (9): 1614-22 Pubmed

 This post belong’s to Dr. Matthew DeLaney’s series on Everyday Risk in Emergency Medicine (EREM).                  

Matthew DeLaney, MD

Matthew DeLaney, MD

Assistant Professor of Emergency Medicine
Assistant Medical Director
University of Alabama at Birmingham
Matthew DeLaney, MD


Associate Professor -Department of Emergency Medicine - University of Alabama at Birmingham