At 48mmol/mol you are just on the first rung of the diabetes ladder and with some dietary changes you should be in a good position to bring it down and keep it there if the dietary regime is one you enjoy as it will be sustainable. I assume at 48mmol/mol you haven't been put on any medication and are being 'allowed' to address your blood glucose level by some lifestyle changes. Some modest changes may be all that is needed.
The testing you do has to be for a purpose and give you information on which to act upon.
Many test in the morning to monitor daily or weekly progress as if you make the changes you should see improvement in those levels over the weeks.
People also test to find out if their meals are tolerated as if the increase in blood glucose following your meal is kept to a low level then overall level will improve. Many test before they eat and after 2 hours aiming at an increase of no more than 2-3mmol/l, if it is more than that then the meal is too carbohydrate heavy for your body to tolerate and you would need to reduce the carbohydrate component of the meal. As your levels come down then no more than 8-8.5 mmol/l 2 hours post meal is a good place to be and 4-7mmol/l before meals or fasting/ morning level.
Unless you are on medication which could produce low blood glucose that is fairly unlikely to be an issue.
That is when people might test at night.
But everybody will have a testing regime which suits them and that may change as time passes since diagnosis.
Have a look at this link as it may clarify things for you.
https://lowcarbfreshwell.co.uk/
It is a low carb approach which many have found successful at reducing blood glucose and losing weight