When Is A Guinea Pig Fully Grown? (Owner’s Guide)

Are you a proud owner of a guinea pig, or are you considering adopting one as a pet? If so, one of the questions you may have is about when your furry friend will reach full size.

After all, it’s important to know when your guinea pig will be fully grown so that you can provide appropriate care and ensure they live a healthy and happy life.

Guinea pigs are incredibly popular pets, thanks to their adorable looks and friendly personalities. T

hey are social animals that enjoy interacting with their owners and other guinea pigs, and they make great pets for people of all ages.

However, despite their popularity, many people don’t know much about guinea pig growth and development. That’s where we come in.

A guinea pig is considered fully grown between six months to two years of age. The time of growth depends on the breed, genetics, and gender. Fully grown guinea pigs exhibit physical changes like the presence of sacs in males and matured genitalia in females.

In this article, we’ll discuss everything you need to know about guinea pig growth and when your pet will reach its full size.

We’ll cover factors that affect growth, signs that your guinea pig is fully grown, and differences between male and female guinea pig growth. Plus, we’ll provide tips on caring for fully grown guinea pigs to keep them healthy and happy.

So, whether you’re a seasoned guinea pig owner or a newbie looking to adopt a furry friend, read on to learn everything you need to know about guinea pig growth and development.

Understanding Guinea Pig Growth

Guinea pig growth is a fascinating topic, and understanding it can help you better care for your furry friend.

Like most animals, guinea pigs go through several stages of growth, from infancy to adulthood.

The rate of growth can vary depending on factors like breed, genetics, and gender, so it’s important to know what to expect at each stage.

Baby guinea pigs, also known as pups, are born with their eyes open and fully furred.

They are typically weaned from their mother’s milk between three and five weeks of age and can begin eating solid food.

During this time, they will grow rapidly, putting on weight and developing their muscles and bones.

As pups reach three months of age, they enter the juvenile stage. This is when they start to lose their baby teeth and grow in their adult teeth.

They also start to become more independent, exploring their environment and showing off their personalities.

By six months of age, most guinea pigs have reached full size, but they are not considered fully grown yet.

This is because they are still developing their muscles and bones, and their organs are still maturing.

Depending on the breed and genetics, guinea pigs may continue to grow until they are two years of age.

It’s important to monitor your guinea pig’s growth and weight to ensure they are healthy.

Overfeeding or underfeeding can lead to health problems, so it’s important to provide a balanced diet and plenty of exercise.

By understanding guinea pig growth and development, you can provide the best care for your furry friend and enjoy watching them grow into a happy and healthy adult.

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Factors Affecting Guinea Pig Growth

Guinea pig growth can be affected by several factors, including breed, genetics, diet, and environment.

Here’s a closer look at each of these factors and how they can impact your furry friend’s growth:

Breed: Different breeds of guinea pigs have different growth rates and sizes. For example, the American guinea pig is one of the larger breeds, while the Abyssinian guinea pig is smaller in size. It’s important to research your guinea pig’s breed to understand what size and growth rate to expect.

Genetics: Just like with humans, genetics can play a role in guinea pig growth. Some guinea pigs may be predisposed to certain health conditions that can impact their growth, while others may grow more quickly or slowly than average.

Diet: A healthy diet is crucial for guinea pig growth and development. Providing your furry friend with a balanced diet that includes hay, fresh vegetables, and commercial pellets can help ensure they are getting the nutrients they need to grow and develop properly. Overfeeding or underfeeding can lead to health problems, so it’s important to monitor your guinea pig’s food intake.

Environment: The environment your guinea pig lives in can also impact their growth. A clean and spacious cage, regular exercise, and access to fresh air and sunlight can all help promote healthy growth and development. Stressful or crowded living conditions, on the other hand, can have the opposite effect.

Signs of a Fully Grown Guinea Pig

Once your guinea pig reaches adulthood, there are several signs to look out for to determine if they are fully grown. Here are some of the key indicators:

  • Size and weight: Guinea pigs reach their full size by six months to two years of age, depending on their breed and genetics. Once they have reached their adult size, they will generally maintain a consistent weight unless there are health issues or changes in their diet.
  • Musculature: As guinea pigs grow and develop, they will naturally become more muscular and toned. Fully grown guinea pigs will have well-defined muscles, particularly in their hindquarters and legs.
  • Sexual characteristics: In male guinea pigs, the presence of matured genitalia and scent glands, also known as anal sacs, indicates that they have reached sexual maturity. In females, the genitalia will also be matured and their vulva will be well-defined.
  • Behavior: Fully grown guinea pigs tend to be more settled and less hyperactive than younger guinea pigs. They may be less likely to dart around and more content to lounge in their favorite spot.
  • Coat: A guinea pig’s coat may also change as they grow and mature. They may develop a fuller, thicker coat as they reach adulthood, particularly during the winter months.

By observing these signs, you can get a good idea of when your guinea pig has reached full maturity.

It’s important to keep in mind that individual guinea pigs may develop at slightly different rates, so it’s always a good idea to consult with a veterinarian if you have any concerns about your furry friend’s growth and development.

Differences between Male and Female Guinea Pig Growth

Male and female guinea pigs can have some differences in their growth patterns due to their biological differences. Here’s what you need to know:

  • Size and Weight: In general, male guinea pigs tend to be slightly larger than females. Adult male guinea pigs typically weigh between 2 to 3.5 pounds, while adult females typically weigh between 1.5 to 2.5 pounds. However, this can vary depending on the breed and genetics of the guinea pig.
  • Age of Sexual Maturity: Male guinea pigs generally reach sexual maturity around 2 to 3 months of age, while females typically reach sexual maturity between 2 to 4 months of age.
  • Pregnancy and Litter Size: Female guinea pigs are able to become pregnant at a younger age than males. Females can have litters of up to 4 or 5 pups, while males obviously cannot become pregnant.
  • Hormonal Changes: Hormonal changes can affect the growth of both male and female guinea pigs. For example, male guinea pigs may develop scent glands near their anus when they reach sexual maturity, which can cause them to appear slightly larger. Female guinea pigs may experience weight fluctuations during their estrus cycle.

Here’s a table to summarize the key differences between male and female guinea pig growth:

Growth FactorMale Guinea PigsFemale Guinea Pigs
Size and WeightSlightly largerSlightly smaller
Age of Sexual Maturity2 to 3 months2 to 4 months
Pregnancy and Litter SizeCannot become pregnantCan become pregnant, have litters up to 4-5 pups
Hormonal ChangesDevelop scent glands, may appear largerExperience weight fluctuations during estrus cycle

It’s important to keep in mind that individual guinea pigs may develop at slightly different rates, so it’s always a good idea to monitor your guinea pig’s growth and development, and consult with a veterinarian if you have any concerns.

Caring for Fully Grown Guinea Pigs

Once your guinea pig has reached full maturity, it’s important to continue providing them with the care they need to live a healthy and happy life.

Here are some tips for caring for fully grown guinea pigs:

  • Diet: Guinea pigs require a diet that is high in fiber, vitamin C, and low in fat. Provide them with plenty of hay, fresh vegetables, and a high-quality guinea pig pellet that is specifically formulated for adult guinea pigs.
  • Housing: Make sure your guinea pig has a spacious and safe living environment. A cage that is at least 7.5 square feet is recommended for one to two guinea pigs. The cage should be kept in a clean, dry area that is away from direct sunlight and drafts.
  • Exercise: Guinea pigs need regular exercise to maintain good health. Providing them with a large exercise pen, or allowing them to have supervised time outside of their cage, can help keep them active and engaged.
  • Grooming: Regular grooming is important for maintaining your guinea pig’s health and appearance. This includes brushing their coat, trimming their nails, and cleaning their ears and teeth.
  • Veterinary Care: Even healthy guinea pigs should receive regular check-ups from a veterinarian to monitor their health and catch any potential issues early on. Additionally, make sure to keep up with vaccinations, parasite prevention, and dental care.
  • Socialization: Guinea pigs are social animals and benefit from regular interaction with their human caregivers. Spending time with your guinea pig, talking to them, and offering them toys and puzzles to play with can help keep them happy and engaged.

By providing your fully grown guinea pig with the proper diet, housing, exercise, grooming, veterinary care, and socialization, you can help ensure that they live a happy and healthy life.

Remember to always observe your guinea pig’s behavior and seek veterinary attention if you notice any signs of illness or injury.


In conclusion, understanding when a guinea pig is fully grown is an important aspect of responsible guinea pig ownership.

Knowing the signs of a fully grown guinea pig, the factors that affect their growth, and how to care for them properly can help ensure that your furry friend lives a long and healthy life.

Remember that every guinea pig is unique and may develop at their own pace. Keep an eye on your guinea pig’s growth and development, and seek veterinary attention if you have any concerns.

As a guinea pig owner, it’s important to provide your pet with the proper care they need to thrive. This includes a healthy diet, a clean and safe living environment, regular exercise, grooming, veterinary care, and socialization.

By following these guidelines and giving your guinea pig the love and attention they deserve, you can create a happy and healthy home for your furry friend. Thank you for reading, and best of luck with your guinea pig!


Hello, I am Mohini, the founder of this blog. I am a qualified Animal Nutrition. I am here to help everyone understand their pets better.

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