No te impacientes

No te impacientes
 

I know it means don't lose patience, but it seems odd to me. I would say no pierdas la paciencia. Is not te impacientes a common usage?

It's not unusual and, although it's used mostly in a more formal register and you will find it more often in writing, it's neutral speech.
"Perder la paciencia" is a more daily speech formula, but "impacientarse" is quite a common verb. :)

So in spoken form,

No te pierdas la paciencia

is OK to use?

It would be "no pierdas la paciencia".
If you say "no te pierdas la paciencia", it means you lose patience with yourself. ;)

Gracias, ADA.