My GSD puppy is underweight. How can I help him gain healthy weight?

Dogs can vary quite a bit in size, even if they are the same breed - so it's more important to look at your dog's body condition to determine if he is under (or over) his ideal weight rather than comparing to averages for the breed. Ideally, you should be able to feel his ribs easily with your hands when you run them down his sides, and he should have a visible "waistline" or abdominal tuck just behind the ribcage. The ribs and hipbones should not be visibly jutting out of his fur, as this would be a sign that he is too thin.

If his body condition is normal, I would not recommend increasing his food or trying to make him gain weight, as it's not good for growing dogs to be overweight at this age - it's very hard on their joints and can predispose them to orthopedic problems such as hip dysplasia later in life. If you're unsure if he is the correct weight for his size, you're welcome to request a consultation with one of us and share some photos of him - we would be glad to try and help :)