How much does one tbsp MCT and ghee raise blood glucose/insulin?

The retrieved studies do not directly measure how much 1 tbsp of MCT oil and ghee raises blood glucose or insulin in a fasting human. The answer must be inferred from indirect evidence.

No study in this retrieval tested that exact dose in people. The closest mechanistic evidence comes from a narrative review noting that octanoate, a main MCT component, raises blood glucose via hepatic gluconeogenesis in animal models [1]. That suggests MCT could cause a small glucose rise, but the size is unknown. Ghee (mostly long-chain saturated fat) has no known direct glucose-raising effect.

For insulin, a rat overfeeding study found that an MCT diet produced lower serum insulin than a long-chain triglyceride diet (85 vs 118 μU/ml) [2]. That is chronic, not acute, but it hints that MCT does not strongly stimulate insulin. Human studies on mixed meals show that adding fat to carbohydrate blunts the glucose spike and reduces the insulin response [3], but that is with carbs present. In a pure fast, adding only fat should provoke little to no insulin release.

The bottom line: the evidence cannot give a number. Based on mechanism, any glucose rise from MCT is likely small (single-digit mg/dL at most), and insulin should remain near fasting levels. The practical effect on a fast is negligible for glucose/insulin, though MCT will raise ketones and break a strict fast.

My call: the evidence does not quantify the rise. Confidence: low, because no human study with this dose exists in the retrieval.