There are no blood tests for Bipolar Disorder. A doctor may take blood to rule out physical illness (like Thyroid insufficiency) but there is no test for Bipolar. Bipolar has a genetic component so if you think something is wrong but there is no history of Bipolar in your family, it's most likely something different (like Borderline Personality Disorder). If you have the genetic predisposition for Bipolar it can manifest on it's own or traumatic life events can trigger it, but the genetics have to be there first. You cannot "catch" bipolar.