HI
@Gaffer type 1,
On my reading, experience as a TID but not as health professional advice or opinion:
Not sure how long after the evening meal you tested your BSL.
In various posts people on insulin for Type I or LADA diabetes, have noted that meals with foods like pasta and lentils seem to take longer to reach a BSL peak, particularly with fat in the meal such as eggs, chicken with skin etc - 3 to 4 to 5 hours are mentioned as the peak BSL time after such a meal.
As far as the short acting insulin before the meal - if you search for "pictures of short-acting insulin profiles" you will see graphs showing the onset, peak and duration of the insulin's action. The peak action is often around the 2 to 2 1/2 1/2 hour mark and the duration about 5 hours.
But if so, the peak BSL from the meal noted above may well be happening an hour or more after the peak action of the insulin and nearer the end of the short acting insulin's duration.
Also these profiles are averages of how the insulin might work in someone.
The following table shows the range of onset, peak and duration of a particular short acting insulin.
You will see how much the range of onsets, peaks and duration can vary between individuals. You would need to discuss with your health team how to best sort it what the onset, peak and duration of your short acting insulin may be and also whether these figures are the same say, for the same insulin before breakfast and lunch also.
Secondly: as a general rule the smaller the dose of short acting insulin the shorter its duration, the lower and earlier the peak might be compared to a larger dose as the following graph shows:
So a dose of 4 units of short-acting insulin before a meal is not likely to easily cover a meal with a delayed peak BSL.
I hope the above might explain some of the possible reasons for your BSL troubles.