Blood glucose levels move throughout the day. Food is a really big factor but also sleep, medication, stress, illness, infection,hormones and other things - even the weather. There is also a thing called dawn phenomenon which basically is your liver adding glucose to,your blood whenever you haven’t eaten for a while (most commonly overnight).
This gives you an idea of what various levels might represent.
https://www.diabetes.co.uk/diabetes_care/blood-sugar-level-ranges.html . Remember though meters are not precise and have one room for error and a one off is just that. Look for trends and patterns instead.
Starving yourself isn’t a good plan. intermittent fasting is a much more planned thing and doesn’t mean starving.
