Whether you've got puppies or younger dogs, it's important to monitor their growth. Sure, it takes some dog breeds and individual dogs longer to grow than others, but a complete standstill can indicate serious health issues. Research your dog's breed and call a veterinarian if you're worried.
During their first couple of weeks of life, puppies may not appear to grow much. After that, you can expect them to get bigger and bigger for the first six months of their lives. As a general rule, puppies should gain 50 percent of their body weight per week from the time they're 2 weeks old until they're 4 weeks old. After that, growth should remain fairly steady through the weening period, which generally lasts until they're 8 weeks old. After that growth varies from gradual to dramatic until your puppy turns 6 months old and becomes a young dog.
Young dogs continue growing from the time they're half-a-year old until they're 1 year old or, in some cases, 1-and-a-half years old. As with older, puppies, growth can creep up or come in spurts -- sometimes both. Regardless of whether growth is fast or slow, your dog should continue getting bigger until she reaches the average breed weight, which you can look up on the American Kennel Club's website. Larger breeds tend to take longer to reach their full size than their smaller brethren. It's not unusual for them to fill out when they're closer to 2 years old.
Puppies and young dogs require roughly twice the calories and nutrition as adult dogs. Mother's milk helps, but beginning around the time they're 4 weeks old, it's up to you to supplement food (and growth). The easiest way to make sure your dog has proper nutrition for proper growth is to buy commercial puppy food with the words "complete" and "balanced" on the label. Food type and amount is dictated partially by breed. Ask your vet or visit the American Kennel Club's website for general feeding guidelines. It's tempting to feed your growing dog the maximum amount of food for her breed. Instead, use the average amount to ensure average growth, as recommended by the Virginia-Maryland Regional College of Veterinary Medicine, among others. This helps prevent canine obesity or over-nutrition.
If it seems like your dog isn't growing or isn't growing as fast she should, call a veterinarian. Plenty of congenital and acquired conditions exist that can stop or slow growth, so it's better to be safe than sorry. This is true especially with nursing puppies, as the mother's health could be affecting her litter. Contrary to popular belief, there's no such thing as the "runt" of the litter. A puppy or young dog that's not growing could have serious, potentially fatal health issues.