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Does size matter? And can it be predicted?

At least three to four times a week, we are asked, “how much will that puppy weigh?” Well, I am a bit sarcastic of a person. I do try not to be rude, however. Honestly, I am not a wizard and cannot foresee the puppy’s future. I can give you the fact about the puppy at this moment. For example, a responsible breeder will tell you the parents and maybe the grandparent’s weight. Please think about this in the context of a human. We know that no Doctor can accurately predict our child’s height or weight in adulthood. Why do people think dog breeders can? The answer is because of “THE CHART.”

Yes, THE CHART is this graph of someone (nobody knows who, and there are many charts) that if a puppy is born X weight, it will be X weight as an adult. But how can it do that? What predicts size? It’s more than just genetics. Let’s look at a few.

1. Genetics does play a role, but we inherit unevenly from our ancestors. So, each puppy in a litter will have different genes that control size. We know about Body size Genetics and do tests for that, but even with this science, it’s not a sure thing.

a. Five known genes play a part in what size our canine is.

i. Body Size (IGF1) This is fixed and doesn’t vary for Chihuahuas

ii. Body Size (IGFR1) We can have three different sizes here Larger GG, Intermediate CA or CG, and Smaller.

iii. Body Size (STC2) This is fixed for Chihuahuas

iv. Body Size (GHR - E191K) This is fixed for Chihuahuas

v. Body Size (GHR - P177L) We can have three sizes here Larger CC, Intermediate CT or CG, and Smaller TT

b. We are still learning how these genes interact with each other, and we are currently tracking adult weights and comparing them to the results of their DNA testing.

2. Diet plays a significant role in the size of a dog. We know if the dog needs better-quality food and gets lots of snacks, it will be overweight. This also follows with if the dog is underfed, the dog may be sickly and thin. Both are something the breeder would not know before you have possession of the puppy.

3. Exercise is essential to overall health. Before your puppy is finished growing can affect oversize as much as too little.

4. Some lines of dogs will go to mature size faster than other lines, which are typically called slow maturing lines. There are pros and cons to both. I have experienced a 6-month-old puppy be at its total mature weight of 5 lbs. and never gain more (this dog is now five years old and the same wt) times; it takes two years for a dog to mature and be finished growing fully. I find you must have patience with this as a breeder. I see a lot of breeders give up on a dog for being a breeding/show prospect for under a year when honestly, they have not even the dog enough time to fill in and finish growing.

5. Illness can cause a dog not to grow to full adult size. When we are sick, our body robs resources to fight to stay alive. Growth is not a priority when we are sick, getting over an infection, or many other conditions that can tax a 1-2lb puppy’s body.

6. In all honesty, 99% of people can’t tell the difference even when picking up a 4lb dog vs. a 6lb dog. We have tested this theory, and almost 100% of people are wrong when predicted by visually and by lifting the wt. Body structure and style can make one dog look heavier when it is not, and another appear lighter than it is.


I have had 1.8oz puppies grow to be 9 lb healthy adults, and I have had a 6oz puppy grow to be barely 4 lbs. There are too many environmental influences in the dog’s life that are out of the breeder’s control to be able to help a puppy buyer in this case. I am 5’3” and have had C4-L2 in my spine fused and reconstrued with cadaver bone and metal. I can comfortably carry a 6lb chihuahua as my medical service dog all day. So not many reasons a 4-6lb chihuahua will be too heavy. So, what to ask a breeder? A typical size of a Chihuahua at ten weeks old is 15 oz to 2lbs… this is normal. Please don’t be fooled into thinking it is rare or unique.

1. How big are the parents

2. How big are the grandparents? (If the breeder knows)

3. What is the weight of this puppy today?

Also, understand that in Chihuahua, a standard size is honestly no matter the birth weight is 4-6lbs (if kept a perfect weight and never been sick). This is a healthy weight.

Tiny Chihuahuas that stay under 3 lbs are rarely healthy and do not happen at full maturity often. Most of the time, when I see a dog being advertised as super small, it is honestly just a standard size that someone is trying to get more money for. Besides, who wants to pay more for a dog requiring more medical attention, vet bills, and constant care?

I will be posting more about what the hardships that come with an under 3lb dog soon.

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