Does mct oil break a fast?

A 15 ml (1 tbsp) serving of MCT oil has about 130 kcal and 14 g of fat. Fat carries about 9 kcal per gram, so the 14 g of fat accounts for nearly all of the energy. MCT stands for medium-chain triglycerides.

On the four goals this site uses to sort answers, MCT oil breaks a fast for weight loss, autophagy and gut rest. It is safe for blood sugar. A tablespoon is well over the common 50-calorie rule of thumb, which is not an official limit. Autophagy is the strictest goal, so 130 kcal of anything counts. Your gut has to digest and absorb the oil, which ends a gut-rest fast. The oil is almost pure fat, with no sugar or starch to raise blood glucose.

Smaller amounts change the numbers but not the verdicts. A 5 ml teaspoon is about 43 kcal, close to the 50-calorie line. A bulletproof coffee made with a tablespoon of butter and a tablespoon of MCT oil comes to about 230 kcal, which is a small meal.

MCT oil is popular with people who want ketones. A review of studies in healthy adults found that MCTs can bring on ketosis without a ketogenic diet or a long fast. The studies were small, so the evidence is early. Higher ketones do not cancel the calories, so the weight-loss verdict stays the same.

Gut trouble is the usual side effect. A 2026 review of 33 studies with about 1,100 people found gut symptoms were the most common, mainly diarrhoea, stomach pain, discomfort and nausea. Moderate to severe reactions were not unusual, especially at higher doses. The ketone review above advised starting with a small amount. If you use MCT oil, keep it for your eating window and start low.