In general, cream of mushroom soup is not keto. While you know I like to avoid calling foods "keto" or "not keto," (ketosis is a metabolic state, not a food) traditional cream of mushroom soup is not keto friendly. Just a half cup of the most popular brand contains eight grams of carbohydrates.
Not only do most canned cream of mushroom soups have thickeners containing an amount of carbs that could kick you out of ketosis, many of them also have vegetable oils and other questionable ingredients.
Some common ingredients in canned cream of mushroom soup include cornstarch, MSG, canola and/or soybean oil and wheat flour. Even "cleaner" brands may contain thickeners that increase the carb count.
As always, if you're using a prepared food product, read the label carefully. Hidden carbs are everywhere, especially in the over 60 different names for sugar.
Download our handy sugar names guide to store on your phone to have on hand while shopping.