If you’re aiming to get morning blood sugars of 5-6 mmol then you need to be going to bed between 5-6 mmol, presuming that your basal is set correctly to keep you stable. If you’re rising throughout the night and waking up higher than you wish then upping the tresiba is the answer. It depends what level you’re going to bed at really, as if you’re going to bed at a higher range then you don’t want to up the tresiba and use it to pull you down overnight, as that’s not it’s job. It should keep you stable.