We aren't allowed to give medical advice here so all I can tell you what I would do in my position, which may well be different to yours. Really this is the sort of question that your diabetes team should have answered for you.
Can I ask what type of diabetes you have and what sort of insulin regime you are on?
As a T1 on insulin, now on a pump and previously on MDI (multiple daily injections) I might reduce my insulin by a small correction dose (my pump likes me to have a bg of 6 so does it automatically) and leave it till the actual start of the meal rather than prebolusing.
For me I would Inject as normal based on the carbs i will eat, 5 is a perfectly normal bg reading..
if you prefer to run slightly higher you could take slightly less insulin
If you are lower than 5 you could reduce your dose slightly in the same way that if you are too high you can add insulin
Assuming your insulin dose carb to insulin ration is correct you shouldn’t have an issue, but as always keep an eye on your BG
Questions like this can be asked to you care team who can advise on corrections and when to correct and by how much - everyone is different so ‘how much’ is individual
When I was using Novorapid, I would have injected as usual. On Fiasp, I would inject after the meal, otherwise I would go hypo, due to its quick action time.