Hallucinations are the perception of something that doesn’t exist. They can be auditory (heard), visual (seen), tactile (felt) or olfactory (smelled).
These hallucinations can have many causes. The most common causes are recreational drugs and dementia or delirium but they can also be caused by high fevers or certain illnesses. Some people who have survived serious, life-threatening illnesses, like septic shock, report having very vivid hallucinations while they were in the intensive care unit (ICU).
Hallucinations in the ICU are now recognized as relatively common, often frightening experiences. Researchers are beginning to understand how they arise and how long their psychological effects can last. A large ICU study published in 2025 found that hallucinations affected about one in 12 patients (8.3%). Another study reported hallucination rates in the range of roughly 7% to 16% of critically ill patients.
Hallucinations are also a change in mental status. This could be a sign of sepsis.
Sepsis, which was often called blood poisoning, is the body’s life-threatening response to infection. Like strokes or heart attacks, sepsis is a medical emergency that requires rapid diagnosis and treatment.
Suggested Citation:
Sepsis Alliance. Sepsis and Hallucinations. 2026. https://www.sepsis.org/sepsisand/hallucinations/
Updated July 17, 2026.
