Hi xmas,
My DSN suggested missing a meal out (and missing the short acting that went with it) to check whether the background insulin was working right. If it's right, then missing the meal and the short-acting insulin shouldn't affect your sugar levels.
The way that background is typically changed is to get the morning blood sugar level right, then adjust the short acting insulins to take account of the meals - often starting at a ratio of 1 unit of insulin to every ten grammes of carbohydrate. The ratio might be different at breakfast, at lunch and at dinner, but 1u to 10g is a starting point.
It's important, as others have said, to work out a pattern for what your sugars are doing rather than reacting to only one reading.
When you were first diagnosed, the regimen was probably take this many units and this much carbohydrate and that'll be fine. I know that it was with me! Now, there are many other factors that are involved, from basal/bolus to dawn phenomenon. It's become a complicated world with what we've apparently learned!
Steve