End of Life Concerns An Overview of Level of Consciousness (LOC) LOC is an abbreviation describing patient awareness, alertness, and wakefulness By Angela Morrow, RN Angela Morrow, RN LinkedIn Angela Morrow, RN, BSN, CHPN, is a certified hospice and palliative care nurse. Learn about our editorial process Updated on May 17, 2023 Medically reviewed by David Strosberg, MD Medically reviewed by David Strosberg, MD David Strosberg, MD, is board-certified in Vascular and General Surgery and is an assistant professor of surgery in Yale-New Haven Hospital's Vascular and Endovascular Surgery Division. Learn about our Medical Expert Board Fact checked by James Lacy Fact checked by James Lacy LinkedIn James Lacy, MLS, is a fact-checker and researcher. James received a Master of Library Science degree from Dominican University. Learn about our editorial process Print Level of consciousness (LOC) is a medical term used to describe how awake, alert, and aware you are. It also refers to how well you respond to attempts to get your attention. A person with an altered level of consciousness may have decreased cognitive function or be difficult to arouse. A variety of medical conditions and drugs can affect your level of consciousness, from having dementia or lethargy, to being in a coma. Sometimes impaired consciousness is reversible, while other times it is not. This article covers normal and altered states of consciousness as well as coma classifications. Caiaimage / Sam Edwards OJO+ / Getty Images Normal Level of Consciousness Medical definitions say a normal LOC means you're either awake or can be readily awakened from normal sleep. Terms include: Consciousness: A state in which you're awake, aware, alert, and responsive to stimuli. Unconsciousness: A state in which you have a deficit in awareness and responsiveness to stimuli (touch, light, sound). Sleeping isn't considered unconsciousness if waking up would result in normal consciousness. Between these two extremes are several altered levels of consciousness. They range from confusion to coma, each with its own definition. Consciousness: A Neurological Explanation Altered Level of Consciousness Altered or abnormal levels of consciousness are states in which you either have decreased cognitive function or can't be easily aroused. Most medical conditions affect the brain and impair consciousness when they become serious or life-threatening. An altered LOC usually signals a serious medical problem. Often, an altered LOC can deteriorate rapidly from one stage to the next. They require timely diagnosis and prompt treatment. Confusion Confusion describes disorientation that makes it difficult to: ReasonProvide a medical historyParticipate in a medical examination Causes include: Sleep deprivation Fever Medications Alcohol intoxication Recreational drug use Postictal state (recovering from a seizure) Delirium Delirium is a term for an acute confused state. It involves impaired cognition (thought processes) and may include: Attention deficitsSleep-wake cycle changesHyperactivity (agitation) or hypoactivity (apathy)Hallucinations (seeing things that are not there) or delusions (false beliefs)Heart rate and blood pressure instability Causes can include: Alcohol withdrawal Recreational drugs Medications Illness Organ failure Severe infections Delirium Risks and Effects Lethargy and Somnolence Lethargy and somnolence (sleepiness) involve: Severe drowsinessListlessnessApathyReduced alertness A lethargic person may need a gentle touch or verbal stimulation before they'll respond. Causes can include severe illnesses or infections, recreational drugs, and organ failure. LOC SYMPTOMS CAUSES Normal WakefulnessAwarenessAlertness Confusion DisorientationInability to reason Sleep deprivationFeverDrugs/alcoholSeizure recovery Delirium Impaired cognitionHallucinationsDelusionsAgitation or apathyUnstable heart rate and blood pressure Alcohol withdrawalDrugsIllnessOrgan failureSevere infections Lethargy and somnolence Severe drowsinessListlessnessApathyReduced alertness Severe illnessSevere infectionDrug useOrgan failure Obtundation Reduced alertnessSlow responses to stimuliProlonged periods of sleepDrowsiness while awake PoisoningStrokeBrain swellingBlood infectionAdvanced organ failure Stupor Minimal response to vigorous stimuli StrokeDrug overdoseLack of oxygenBrain swellingHeart attack Coma Unresponsiveness to all stimuliMay lack gag reflex, pupil response Severely diminished brain functionExtreme blood lossOrgan failureBrain damage Obtundation Obtundation is reduced alertness with: Slow responses to stimuliNeeding repeated stimulation to maintain attentionProlonged periods of sleepDrowsiness between these periods Causes can include: Poisoning Stroke Brain edema (swelling) Sepsis (a blood infection) Advanced organ failure Stupor If you're in a stupor, you respond minimally to vigorous stimulation, such as a pinched toe or light in the eyes. Causes can include: Stroke Drug overdose Lack of oxygen Brain edema Myocardial infarction (heart attack) Coma Someone in a coma doesn't respond to any stimuli. Their pupils may not react to light, and they may not have a gag reflex. Comas are caused by severely diminished brain function. This is usually due to: Extreme blood lossOrgan failureBrain damage What Is Myxedema Coma? The causes of these altered LOC may overlap. For example, the early stages of brain edema or organ failure can cause confusion. But you can then advance rapidly through the stages of lethargy, obtundation, stupor, and coma. Classifications of Coma Levels of consciousness can be subdivided into levels that further clarify your degree of unresponsiveness. Several systems have been developed to standardize these classifications. That helps improve communication among healthcare providers and aids in research. The most common classification systems are: Grady Coma Scale: Grades a coma from I to V. It's based on your state of awareness and response to stimuli (your name being called, light pain, deep pain). Grade I indicates confusion, while V indicates coma (no response to stimuli).Glasgow Coma Scale: Scores the level of consciousness from 1 to 15, with 15 being normal LOC. This scale takes into account verbal, motor, and eye responses to stimuli. Summary Levels of consciousness range from normal alertness and attention through many altered states. It starts with confusion and delirium to stupor and coma. The same things may cause a milder state of altered LOC that can cause more severe states. Sometimes, you may start with a mild state and rapidly progress through to a higher stage. Coma scales can help describe the exact level of consciousness. A Word From Verywell If you or someone you know has an altered state of consciousness, it's important to get medical help. These states don't come on without a reason, and most causes pose real threats to your health. If you're at risk for altered LOC, be sure you have the proper medical precautions in place. For example, wear a medical alert bracelet or have an app on your phone that lists your diagnoses, medications, and emergency contacts. Some can be accessed even when your phone is locked. You may also want to designate a healthcare proxy to speak for you when you're unable. This is especially important if your close family members don't agree with your wishes. Best Medical Alert Systems 5 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Tufts Medical Center. Altered level of consciousness. Cleveland Clinic. Delirium. Merck Manual Professional Version. Overview of coma and impaired consciousness. Opara JA, Małecka E, Szczygiel J. Clinimetric measurement in traumatic brain injuries. J Med Life. 2014;7(2):124-127. Reith FCM, Lingsma HF, Gabbe BJ, Lecky FE, Roberts I, Maas AIR. Differential effects of the Glasgow Coma Scale Score and its components: An analysis of 54,069 patients with traumatic brain injury. Injury. 2017;48(9):1932-1943. doi:10.1016/j.injury.2017.05.038 Additional Reading Vasilevskis EE, Chandrasekhar R, Holtze CH, et al. The cost of ICU delirium and coma in the intensive care unit patient. Med Care. 2018;56(10):890-897. doi:10.1097/MLR.0000000000000975 By Angela Morrow, RN Angela Morrow, RN, BSN, CHPN, is a certified hospice and palliative care nurse. See Our Editorial Process Meet Our Medical Expert Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit By clicking “Accept All Cookies”, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Cookies Settings Accept All Cookies