What is the safest way to help an underweight rescue dog gain weight?

A dog that has been significantly underfed can have a digestive system unused to processing normal or large meals, so introducing too much food too quickly risks vomiting, diarrhea, or general digestive upset.

Starting with smaller, more frequent meals, perhaps four or five times a day initially, and gradually consolidating toward a normal two or three meal routine as the dog's system adjusts, tends to work better than a fast increase.

A vet visit soon after adoption helps establish whether the underweight condition has an underlying medical cause beyond simple undereating, which is important to rule out before assuming food alone will solve it.

Your vet can also help set a realistic, safe pace and target weight based on your specific dog's condition and history where known.

Increase the daily amount gradually, roughly 10 to 15 percent every one to two weeks, rather than jumping to a full calculated amount immediately.

Track weight weekly in the early period, since this is a time when close monitoring helps catch whether the increase is being tolerated well and is actually leading to steady, healthy gain. Weekly checks also give you the confidence that the plan is working, which matters during what can otherwise feel like a slow, uncertain process for both you and a dog still settling into a new home.