My family member, let's call them Alex, was diagnosed bipolar around 2012 after being admitted to the mental hospital for several days following a manic episode. They've been on lithium for years. 
Two years ago Alex had a manic episode that I personally witnessed and they were in the behavioral unit for a week before they finally started coming out of it. 
Just recently I found out that Alex stopped taking lithium along with their prescribed sleeping pills and other medications because they're 'doing better now' 
The reason I found this out is because I was with Alex a few days ago and they were acting really strange, giving me signs that they may be going into a manic episode. 
I asked them if they were taking their medicine, and they informed me that their doctor took them off all medications and even said that he thought Alex was misdiagnosed bipolar...but that is simply not true. 
Yesterday Alex and I were in the car together and Alex saw a plane and was convinced it wasn't moving (it was an optical illusion). They immediately started panicked and saying things that didn't make sense. 
Ever since this Alex has been constantly saying things out of nowhere that don't make sense. I know where this is going, I'm just scared we won't be able to get them back on medication in time without sending them to the mental hospital.
I also don't know if Alex would agree to admit themselves at this time. I'm extremely stressed about this. All advice requested.