Type 1 Why can’t you inject until 4 hours?

Because that’s typically how long it takes fast acting insulin (like novorapid) to be out of your system. I don’t ever inject if it hasn’t been 4 hours since my last novorapid because I don’t like stacking doses, stacking tends to lead to lows then highs then lows then highs. I find it’s best to give it the 4 hours to work.

I inject as little as 2 hours..

If I have under estimated my food intake and my bg is the same or higher after 2 hours I will have more

But as said above it can last in your system for upto 4 hours so if you dont allow for this you could end up having a hypo

Another thing I was told was never inject without food.. but I do if needed