How can I help my partner when they are in a manic state?

The answer has here everything to do with whether your lover is in a full manic state or a hypomanic state. There are such broad ranging differences in awareness, judgment and self-control during elevated mood states. Where your lover is positioned on this continuum has everything to do with the kinds of adjustments or interventions that are possible.

If his or her mood elevation is mild to moderate (hypomanic) then your lover may still have the capacity to receive your concerns, consider their merits and make appropriate adjustments. But if the elevation has progressed to full mania, then the individual is often not able to bring things under control without some measure of external help - usually in the form of medication adjustment, addition of antipsychotic medication and possibly even short-term hospitalization.

If you are in an on-going committed love relationship with someone who has bipolar I, it's helpful to have "plans for manic episodes" in place prior to the onset of mania. One important aspect of this plan would be to have contact information for your lover's psychiatrist so that you may call him/her and provide accurate information about your lover's current manic symptoms. If a release of information has been signed ahead of time, then the psychiatrist or mental health professional will also be able to share information with you that may facilitate your efforts to help your lover. But the key is to have fall back options already in place in the event your lover does experience significant mood destabilization.