To answer your questions:
- You do not have to wait for BG to rise before eating a biscuit. You can have it straight away.
- Once you BG has risen above 4 (which should only be minutes), you can take your insulin for lunch as usual.
The only thing I would add is to try to understand your hypo.
- Why did it happen? Did you have too much insulin for the amount of food you ate or have you been especially active? This is something to consider in the future and for you to adjust your insulin and/or BG before exercise.
- Is 3.9 the bottom of your BG or do you know if it is falling further? Unless you have a CGM or Libre, this is not easy to measure apart from keeping an eye on your BG. If you have taken some insulin in the last two hours or so, you still have insulin on board (IOB) which will cause your BG to continue to fall. If you have just nudged down to 3.9 after a long period, you are less likely to continue falling.
Finally, unfortunately, our BG meters are not very accurate. Therefore, although your meter is reading 3.9, you may be 4.0 and not hypo. The reason I say this is to put the hypo in perspective ... you still did the right thing by treating it.
