1) don't basal test for a whole day, during an extended fast you might get a liver dump pushing blood sugar up and making the basal test unreliable. Instead do a night, morning, afternoon and evening test. So if your testing for the morning just skip breakfast and finish off with a late lunch or if your doing afternoon have an early breakfast so you've got 4hours food and bolus free then start the test and skip lunch and finish up with a late dinner.
2) don't eat when basal testing. It's all well and good saying carb free snacks but in reality anything vaugely edible but carb free is likely to have a decent amount of protein in, if youre not eating carbs your body will work to turn protein into glucose and that will raise your blood sugar, making a basal test unreliable.
By all means go with what your DSN has said, but most literature now states that a basal test has to be a fasting one, the author of the book Think Like a Pancreas covers the Do's & Don't of a basal test:
Well they said to split the day up in to sections like you said, I was just trying to take a shortcut and do it all in one go. I didn't realise the liver might kick in.
But they said I would be ok to eat food that isn't carbohydrate like eggs and meat and things during the test.
I want to do it properly so I will do a fasting test and try and distract myself from eating!
@Nomi I had an ongoing fight with my DSN about whether I should have insulin if the food I am eating contains no carbs. She says they 'wouldn't advise' bolusing for my egg-only breakfast, as they don't contain carbohydrate - even though they raise my blood glucose quite a bit! I chose to ignore her advice and act on my meter instead.
Curiously she changed her tune when I started on a pump and talked about basal testing, for which I was told to fast for parts of days as explained above.
I saw my chance to ask about the eggs again...... Turns out she can't advise people to bolus for carb-free foods, but she DOES advise people to avoid even carb-free food when basal testing as 'even things like eggs can raise blood glucose'!