How Old Is Your Guinea Pig? (And the ONE Thing That Your Pet Store Clerk Gets WRONG!)

How old is your pet cavy? Are you getting a baby guinea pig…or buying a small but full aged adult? Are there different biological markers that separate fully grown animals from those that look alike, but are far younger instead?

The truth is, the best indicator of age when it comes to buying these pets for your family is simple:


You can tell, with high degrees of accuracy the age of your GP purely around it’s weight. (with some degree of natural variance of course, as well)

The first step when trying to “age” your future family companion?

If you would like to know how old your new guinea pig is, you will need to weigh it.

For example, A young cavy that is between two and three months old will weigh 17-18 ounces while an adult will weigh between 24 and 42 ounces.

Once a guinea pig has reached adulthood, it is almost impossible to tell exactly how old they are. At that point, no matter how much experience a pet handler may have, they’re ALL just guessing when it comes age.


The best age to buy your new pet is from five to six weeks old. An experienced rescue operator or breeder will easily locate an animal that is the right age for you. It is doubtful, however, that a pet store clerk will know the age of your pet, even if they appear to be super confident, nice or reliable.

Filed Under: Where to purchase your pet

Buying a new GP, or any new pet for that matter can be an emotional experience. You see the adorable, sweet cavy in the pet store and you hurry back the next day ready to take it home.
Before you write that check to the pet store, you might want to stop and consider the possibility of adopting your piggy from a guinea pig rescue, or purchasing your pet from a breeder instead.

(We like to especially encourage adoption from rescues, because there are so many potential pets without homes, and most rescue operators are very knowledgeable about this cute and cuddly cavy, after all, they have usually chosen to sacrifice a great deal of time, money, and other resources without much hope of financial gain).

First of all, the bottom line at a pet store is profit. For this reason, pet stores are infamous for selling sick or pregnant animals. Many animal lovers charge that pet stores buy their guinea pigs from disreputable breeders who run the equivalent of puppy mills.

Often, animal rights activists have accused pet store owners of selling guinea pigs as food for pet snakes etc.

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