Is Whole Milk Keto?
Whole Milk is not keto-friendly because it is high in carbs. It may kick you out of ketosis even with a small serving size.
Too Much Carbs!
Whole Milk should be avoided on keto because it is very high in net carbs (11.47g of net carbs per 240ml serving).
It is important to limit your net carb consumption to 20g - 30g per day to stay in ketosis. You can calculate your ideal daily net carb allowance by using this keto macros calculator.
As an alternative, you may look for other types of milk that are low in net carbs.
Low in Fats
Whole Milk is both high in carbs and low in fats, which are the exact opposite of the macros required on a keto diet.
The ideal macronutrient ratio for keto is 70% fat, 20-25% protein, and 5-10% carbs. This means the majority of your foods should be both low in carbs and high in fats.