Hi Stu,
To calculate the Lantus dose, don't eat, or inject Novorapid, at least 4 hours before bed. Then compare your bedtime and before breakfast readings. If they differ by more than 1.6 mmol/l then adjust your Lantus by 10% accordingly. A fasting test would be to not eat during a preiod in the day, make sure that you have no Novorapid in you and see what happens to your levels. It's less accurate than an overnight test and means that you go hungry!
Some people report that changing a Lantus dose takes a few days to take affect, but not in my circumstance. Personally, I don't understand how it can as Lantus lasts for 24 hours. So how can a dose taken 3 days ago affect your levels today?
Anyway, I'm less insulin sensitive in the evening that I am in the morning. So if I eat the same meal at lunch and dinner, I'll need more insulin for the dinner-time meal. If your levels are saying you need more insulin in the evening, then the only option is to have more insulin. Perhaps you could calculate an insulin-to-carb ratio for your evening meal and use that ratio for your evening meal only.