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It feels like you just brought your puppy home yesterday – at the same time, you’ll be glad when that sassy, mouthy pup is fully grown.

There’s no exact day on which you’ll notice your puppy has grown into a young lady. From her height, weight, bone structure, teeth and behavior, she’ll mature in many ways during her first year of life.

Here’s the growth stages your puppy will go through, and how you can help her ease into adulthood.

Small Dogs Stop Growing Sooner

Small dogs live longer, but they also grow up faster. Your chihuahua will reach sexual maturity around 6-9 months. If you have an unspayed female, her maturity will be obvious because she will go into heat.

By 8-10 months, your Chihuahua will no longer grow taller, but she may fill out until she’s 2 years old. Filling out doesn’t necessarily mean gaining excess weight.

You may notice her body frame becoming wider, stockier, and her legs may no longer seem as long and lanky. Her ears will become more proportionate, and her neck won’t seem so thin.

When Will Your Chihuahua Lose All Of Her Baby Teeth?

By four months, you’ll start to find your pup’s baby teeth around the house. They might come out when she’s chewing on a toy, eating, or enjoying a treat. Some dogs lose their teeth when they’re outside, some may even swallow them – so you may not actually find any teeth at all.

Regularly check for telltale gaps in your pup’s gums. This is also the perfect time to get your dog accustomed to allowing you to check their mouth and teeth.

Your dog’s baby teeth should be replaced by adult teeth by 6 months. Chihuahuas are prone to having retained baby teeth. Her adult teeth may grow in before their baby teeth fall out. Some baby teeth may never fall out on their own, and may need to be surgically removed.

Matilda still has a baby canine next to her adult canine. Retained baby teeth tend to overcrowd your puppy’s mouth and cause excess tartar buildup. Check daily for tartar and brush away any tartar.

UPDATE: Matilda had her last baby tooth removed when she was spayed. Now, it’s MUCH easier to keep tartar buildup at bay. I wish I would have done this sooner.

When To Quit Puppy Food

Commercial puppy foods have more protein and calories than adult dog food. Puppies can also eat “all life stages” dog foods, or the same raw food you would feed to an adult dog – just in larger amounts than you would feed an adult dog of the same weight.

Regardless of what you choose to feed, you’re going to feed your puppy a lot of it, because she needs the extra nutrition to fuel their growth.

When your puppy has matured, she’ll no longer need the extra calories. You’ll need to switch to an adult formula and/or cut back on meals and portions.

The diet change should be gradual so your puppy can adjust to consuming fewer calories. You can start at 7-8 months.

If you’re feeding three meals per day and preparing to switch to two, offer a small meal or snack for lunch, even if it’s just a few bites of fresh fruits or veggies to hold her over.

By 12 months, your Chihuahua should be fully switched to a two adult-sized portion meals per day.

Training Into Adulthood

Socialization should begin long before your puppy is grown. Different experts have different opinions on a puppy’s critical fear periods. These are periods in which your puppy will be extra susceptible to becoming fearful of new people, situations and other animals.

I don’t agree that you can nail down “7-9 weeks,” and “8 to 11 months” as concrete fear periods because every puppy is different.

The important takeaway is that your puppy’s experiences will have a strong influence on how she behaves throughout her life.

So, while you do want to introduce your puppy to new people, the experiences must not be traumatic.

Keep meetings brief and predictable. Don’t take her to a crowded dog park, introduce her to a gentle, friendly dog you already know. Don’t take her to your city’s huge parade, take her to a friend’s house to meet 1-2 quiet children at once.

When To Celebrate Your Puppy’s Coming Of Age

Depending on your dog’s ethnicity or religion, you may decide to throw your Chihuahua a bar/bat mitzvah, a Quinceañera, or a Sweet Sixteen. Or, you can celebrate her first birthday.

As for a bar/bat mitzah, you should celebrate when your dog is 13 months old – 13 years is simply too long to wait. For similar reasons, a dog’s Quince should be at 15 months, Sweet Sixteen at 16 months.

Because the breed originated in Mexico, it makes the most sense to throw your Chihuahua a Quinceñera, but honestly, your dog probably doesn’t mind, as long as she gets tacos or some other tasty treat.

Does Your Adult Dog Still Have Bad Habits?

By the time your puppy is a year old, she is hopefully already potty trained, and no longer chews up forbidden items.

However, it’s not unusual for Chihuahuas to take longer to potty train.

It’s not unusual for them to still be a bit nippy, and to still get into mischief.

Every puppy learns at her own pace. Even so, bad habits extending into adulthood are a sign that you may need extra help with training.

Review your approach: what’s not working?

You may need to work with a professional trainer. A good dog trainer really trains you to become a better communicator.

Look for a force free dog trainer from the Pet Professional Guild directory. Do not work with anyone who suggests using force, pain or fear to train your Chihuahua.

This is not limited to shock and prong collars – amateur trainers will suggest using spray bottles and cans full of coins to scare your dog.

Every behavioral issue can be resolved with the help of basic animal behavior science. While punishments can work – which is why people use them – they carry a high risk of fallout.

During your Chi’s first year, you’ll develop many unique ways of communicating with one another.

You’ll learn to recognize the instant she gets hungry, when she has to go out, and she’ll always seem to know when it’s time for you to go to work, when you’re sad, and when you need her snuggles.

Raising a Chihuahua is a very special privilege. There will be ups and downs, but once you have a loving, adult Chi who just “gets” you, you’ll hardly remember how you lived without her.

Lindsay Pevny
Lindsay Pevny lives to help pet parents make the very best choices for their pets by providing actionable, science-based training and care tips and insightful pet product reviews.

She also uses her pet copywriting business to make sure the best pet products and services get found online through catchy copy and fun, informative blog posts. She also provides product description writing services for ecommerce companies.

As a dog mom to Matilda and Cow, she spends most of her days taking long walks and practicing new tricks, and most nights trying to make the best of a very modest portion of her bed.

You'll also find her baking bread and making homemade pizza, laughing, painting and shopping.