My Birkenstock Nail Polish has separated, is this normal?

Yes, this is totally normal and doesn’t affect your Nail Polish at all. Sometimes the color in Nail Polish can separate from the other ingredients. Simply give the bottle a good shake before you use it, to mix everything back together. If you’ve shaken the bottle really well and the Nail Polish still isn’t mixing, check how long you’ve had it. Separation can occur when a bottle goes past its shelf life.