If you've given yourself a correction dose, then no, it's not a true basal test. FYI I change my basal almost every day because it varies a lot depending on when I last did exercise. Some days I just can't be ***** to exercise, and sometime I can; therefore I need to adjust my basal regularly.
Here are my rules:
- No eating or injecting around 4 hours before going to bed. Insulin and carbs will interfere with the reading.
- Don't have too much fat or protein the night of the test. Fat can cause a delay in glucose absorption, excess protein is converted into glucose.
- To calculate how much basal you need, calculate the difference in your before bed and before breakfast readings. For every 1.6 mmol/l change adjust your basal by 10%. This calculation is from Gary Scheiner's Think Like a Pancreas. You must buy this book, you will learn loads!
I live by this calculation, it works a treat.
If your pre-breakfast reading is in the teens, you can still use this in your calculation, but there will be a bit of error in it. BG meters are accurate to around 15%, so the higher the reading the less precise. You can use it as an indication that your basal is too high, but you won't get an accurate basal calculation from it.
Finally, if like me your insulin sensitivity changes significantly according to exercise - and if you're lazy like me and can't stick to a regular exercise routine - then change your basal injection time to the morning. This way, if your before bed and before breakfast readings are different, you can act on it immediately, instead of waiting all day to fix it.