Hey Tim. Hope you are well.
Your endo is going from the textbook, but not really putting ALL of it together.
The liver can take up glucose without insulin. It does not use the GLUT4 transport like most of the other tissues and organs. It uses different glucose transporters - GLUT1, GLUT2, and GLUT3. Because of that, it does not need insulin for glucose uptake on the transport level.
So the endo is thinking…your liver released the glucose, and it will take it all back without insulin. Because indeed the liver does not need insulin for uptake.
However what the endo is missing is that glucose uptake by the liver is up-regulated by insulin, and down-regulated by the release of epinephrine, which is what caused your spike.
Insulin stimulates the liver to store glucose in the form of glycogen (glycogen synthesis, or glycogenesis, the storage of glucose as glycogen).
While not necessary for uptake, insulin indeed has several effects which stimulate glycogen synthesis in the liver. It activates the enzyme hexokinase, which phosphorylates glucose, trapping it within the cell. Insulin also activates several of the enzymes that are directly involved in glycogen synthesis - glucokinase and glycogen synthase. In addition, insulin inhibits the activity of glucose-6-phosphatase, which would free glucose.
So your question was about why the endo told you not to correct it.
The difference between the endo’s textbook understanding and the real world application is this:
Endo - The liver is one of the 7 tissues/organs that do not need insulin for uptake, so don’t take insulin! (you can Google this phrase to see them all - “Tissues which don’t need insulin for glucose uptake BRICKLE”)
Real world - Without insulin, the liver’s uptake of glucose is greatly impacted. Take insulin to correct a liver dump and to help the glucose be returned to the liver’s storage.
It is easy to understand in this simple scenario. When would a person’s liver normally take up glucose? When they are in the fed state! When there is food in your stomach, your liver will take up and store.
And what happens when there is food in your stomach? If you are a non-diabetic, there is also insulin in your blood!
So the thing your endo is missing is that insulin, while not necessary for glucose uptake by your liver on a transport level, does play a part in the overall scheme of uptake.
Short answer - if you spike, take insulin,
If you need more details or info, or if I can clarify any of this, feel free to ask. You know how to reach me.