I picked up a couple of 32oz.boxes of organic chicken broth (store brand) from Fresh Market the other day and it claims to have 0g carbs per 1 cup serving.

The ingredients list other ingredients besides chicken stock such as organic vegetable stock, organic carrot, celery turmeric, organic cane sugar, yeast extract, so I would imagine that the entire box would contain some carbs, just less than 1g per cup but all combined could be 8 oz x 4 servings could equal maybe 3g carbs.

The alternative is to buy the common beef/chicken bouillon cubes which might have less carbs but they do have the MSG or preservatives.