Glucose abnormalities and hyponatremia are the two laboratory findings most frequently associated with triggering first-time seizures in adult patients.
Always check an HCG in women who present with their first seizure, as this may reveal the source (i.e. eclampsia) and/or may affect testing, disposition, and initiation of an anti-epileptic drug (AED).
Drug abuse screens should be considered in patients with their first seizure, but no prospective studies have demonstrated benefit from routine use.
References
Turnbull, et al. "Utility of laboratory studies in the ED patient with a new onset seizure." Ann Emerg Med. 1990; 19: 373-77.
Eisner, et al. "Efficacy of a standard seizure workup in the ED." Ann Emerg Med. 1986; 15: 33-9.
