Vancouver Style Guide: Facebook
Reference: #. Author Surname Initials or Facebook name. Title of post or first few words: facebook post url Year Month Day of Tweet [cited Year Month Day] [Facebook]. Available from: Facebook account url.
15. UCD Veterinary Hospital. Milo's story: https://www.facebook.com/ucdvet/20150417/milo 2015 April 17 [cited 2015 May 1] [Facebook]. Available from: https://www.facebook.com/ucdvet
Use a superscript number (like this: ¹) in the text at the place where you are indicating that you are citing from a source.
Milo was treated for a severe abscess on his back and chest wall at UCD Veterinary Hopsital.15