@murrayjohn your avatar says you are type 1, but this post -
http://www.diabetes.co.uk/forum/threads/insulin-doses.124278/ - says that you have been type 2 for 10 years. Which is correct? If you are type 2, being on insulin doesn't make you type 1 it makes you type 2 treated with insulin.
Answers to your questions may change depending on type of diabetes and you can update the type shown in your avatar, or ask a moderator to do so, to correct it.
If you've recently commenced on insulin yes, your hospital should be giving you guidance on dosages. A phone call with your DSN to discuss this seems a sensible way of doing this. I certainly had a few nice games of blood sugar bingo in the first couple of weeks post diagnosis with my DSN.
But unless you are expecting a DSN to follow you round, hold your hand and dial up the pen for you it's probably a good idea to make some effort to understand how your insulin works and how to use it and make dosage adjustments of your own accord.
You're on a basal bolus regime.
Tresiba is the basal, the background insulin. The job of the basal is to keep your blood sugars steady when you aren't eating or bolusing. You can do some testing to see if your basal dosage is doing this by following the guidance here -
https://mysugr.com/basal-rate-testing/ - be aware that if you are adjusting Tresiba any adjustment will need 4-5 days to settle before you try and analyse the impact of the adjustment.
Novorapid is the bolus, the fast acting insulin. The job of the bolus is to deal with food eaten or to correct high blood sugar. It sounds like you are on fixed doses of novorapid. Most type 1s will be given guidance on carb counting or attend a DAFNE course to learn. The bolus will deal with the blood sugar rise cause by carbs. Carb counting involves working out how many grams of carbs 1 unit of insulin can deal with and adjusting meal time doses to take account of how many carbs eaten. There is free NHS course on carb counting -
https://www.bertieonline.org.uk
To correct highs you need to figure out how many mmol/l 1 unit will lower you. The 100 rule is a decent starting point for this -
https://www.uclh.nhs.uk/PandV/PIL/P...ets/Correcting a high blood glucose level.pdf