Although there are no blood or laboratory tests that diagnose adult ADHD, physicians may use various tests to rule out conditions that have symptoms in common with adult ADHD. One simple and inexpensive blood test your doctor is likely to order will check your thyroid hormone levels. Abnormal thyroid levels are very common in women over age fifty and are often mistaken for adult ADHD.

Your doctor may also order tests that measure your Serum CBC count with differential and your electrolyte levels. In general, adult ADHD patients undergo liver function tests before starting stimulant drugs for adult ADHD, the most common type of medication prescribed for the disorder, to ensure their livers are healthy enough to handle the medications.