Dear Mrs Allport,
If you' google' - Novorapid insulin profile pictures - you will see the manufacturing companies 'graph' of how long the blood-sugar-lowering effect of Novorapid lasts and how long after injection it reaches its peak blood-sugar-lowering effect. As you look at various graphs for Novorapid you can see that the peak varies between 1 to 3 hours. The company does its research, other try Novorapid out and you see the variation.
Now, if your injection of Novorapid blood-sugar-lowering effect peaks nearer 3 hours AND the sugar from your meal reaches its peak in your blood at 2 hours, you can see the Novorapid has possibly 'missed the boat' on controlling your BSL. Yes, if you ate food which took a longer time to show up in the blood sugar ( like a bowl of lentils (cooked!) or, in my experience, some Indian take-away food, either with the same carb content as your usual breakfas,t the blood sugar rise might be nearer to co-inciding with your Novorapid's action.
The other point is that if your blood sugar from breakfast peaks before the Novorapid's peak action, then Novorapid may, in its ascendancy of blood-sugar-lowering action, thump your Blood sugar down as the sugar peak from breakfast wanes, and a hypo may happen. Increasing the dose of Novorapid is not likely to help as the mistiming between breakfast sugar peak and Novorapid action peak remains but the ability of Novorapid to bring your blood sugar down increases, risking the occurrence of a worse hypo.
Perhaps discussing these possibilities with your DN and doctor may help you and them to find a solution. Of course my thoughts above are a guess based on your blood sugars and insulin.
Hope that helps. Think of how a sewing machine can drop stitches etc as it loses its timing. Once adjusted the sewing is perfect again !!