What does it mean when a guinea pig grinds their teeth

[LvserxLil]

Ive heard that it is meant to mean a bad sign but my guinea pig Mister Lips does it alot of the time when he is lying in his cage when hes sitting on my lap or bed. Does your guinea pig do it?

 

[DMS260820]

Pain, or angry about something. Thats when mine do it

 

[Julie M]

My old piggie Mango used to do it when he was on my lap. Is it just a quiet sound or is it like the angry teeth chattering?

 

[Merab]

With mine it doesn’t always seem to mean being upset or cross. Jemimah is a champion teeth grinder and I haven’t worked out what she means.
Watch the context as it can mean a variety of things

 

[G&C]

One of my boys starts grinding his teeth when I don’t give him a basil leaf quick enough! I take it mean he’s impatient and hungry.

 

[Freela]

It can be a sign of anger or discomfort, or they could simply be chewing (guinea pigs tend to keep food in their mouths and work at it for a long time on the back molars, as hay is very hard to break down. So even if you haven't seen them eat, they may still have something working back there.)