In many instances, oatmeal can be eaten on a low carb diet.
Diets containing roughly 130 grams or less of total carbs per day can be considered low in carbs, and 1/2 cup (40 grams) of dry oatmeal contains only 27 grams of total carbs — so it can easily fit into a more moderate low carb diet (26, 27).
However, for stricter low carb diets like keto or Atkins, oatmeal contains too many carbs and can easily take up your entire day's carb allotment in a single serving.