It is almost always post-operative shivering: common, brief, and not dangerous.
The Royal College of Anaesthetists describes shivering after an anesthetic as the body's normal response to feeling cold, with muscles rapidly contracting to produce heat. Anesthesia interferes with the brain's temperature control while cool theatre air, exposed skin, and cold IV fluids lower your body temperature, so you shake as you wake up. It usually passes within the first hour, and recovery staff treat it with warmed blankets and sometimes medication. MedlinePlus lists feeling cold and restless as a normal early after-effect of general anesthesia. The key distinction: post-anesthetic shivering happens while you are awake and aware; it is not a seizure.
What to do
Common questions
Why do I shake after anesthesia?
Shaking after anesthesia is usually post-operative shivering, and it looks scarier than it is. The Royal College of Anaesthetists explains that shivering is the body's natural response to feeling cold, with muscles contracting and relaxing quickly to generate heat, and that it is common after general or regional anesthesia, uncomfortable, but not dangerous. It happens because anesthetic drugs disrupt your normal temperature regulation while operating theatres and IV fluids run cool, so your core temperature drifts down. It typically starts in recovery and settles within minutes to an hour, sometimes helped along by warming blankets or, if needed, medication. Shivering is different from a seizure: you are awake and can talk through it. Mention it to your nurse rather than toughing it out, because active warming works quickly. Rarely, shaking that comes back days after surgery, especially with a temperature or wound changes, can signal infection, so that pattern deserves a call to your team.