You may have absence seizures repeatedly for years before heading to the doctor for a diagnosis. You may have "staring spells" without thinking of them as a medical problem or a seizure.
An EEG is a test most often used to diagnose absence seizures. This test records the brain’s electrical activity and spots any abnormalities that could indicate an absence seizure.
These tests also can help to diagnose absence seizures or rule out other conditions:
Blood tests
Tests of the kidneys and liver
CT or MRI scans
Spinal tap to test the cerebrospinal fluid